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Attentional demands of different types of PDA tasks Li, Hiroe 2007

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ATTENTIONAL DEMANDS OF DIFFERENT T Y P E S OF PDA TASKS by H I R O E LI B.A., University of British C o l u m b i a , 2 0 0 5 A T H E S I S S U B M I T T E D IN P A R T I A L F U L F I L M E N T O F THE REQUIREMENTS FOR THE D E G R E E OF MASTER OF ARTS in THE FACULTY OF GRADUATE STUDIES (Psychology)  T H E UNIVERSITY O F BRITISH C O L U M B I A August 2007 © Hiroe Li, 2 0 0 7  Abstract P e r s o n a l Digital A s s i s t a n t s ( P D A s ) are mobile d e v i c e s that offer a range of applications a n d are u s e d in various environments (e.g., finding contact information driving while). T h e s e e n v i r o n m e n t s a n d applications vary o n the level of attentional d e m a n d s . T h e key interests of the present study w e r e to explore the interference that o c c u r s w h e n both the P D A task a n d environment are highly attention d e m a n d i n g . T h e main goal of the present study w a s to investigate the attentional d e m a n d s of two types of P D A t a s k s : Navigation a n d data entry. U s i n g a dual-task methodology, I c o n d u c t e d two e x p e r i m e n t s that explored the amount of attention (Experiment 1 and 2), and two e x p e r i m e n t s that investigated the types of attention (Experiment 3 a n d 4), required by the two P D A task types. F o r the first two e x p e r i m e n t s , a tone discrimination task w a s c h o s e n a s the s e c o n d a r y task a s it has b e e n s h o w n to require g e n e r a l attentional r e s o u r c e s . Participants first completed the tone discrimination task a l o n e in order to a s s e s s p e r f o r m a n c e in the baseline condition. In the test p h a s e , participants completed a set of P D A t a s k s concurrently with a tone discrimination task. T o a s s e s s the type of attention required by P D A t a s k s , a method u s e d to reveal the types of attention w a s first validated in Experiment 3. T h e validated method w a s u s e d in E x p e r i m e n t 4 . Participants completed a task that either drew o n visuo-spatial r e s o u r c e s or articulatory/auditory r e s o u r c e s concurrently with either a P D A navigation or data entry task. T h e two main findings of the 4 experiments w e r e : Navigation requires more attention than data entry; d a t a entry requires more articulatory/auditory r e s o u r c e s while navigation requires both articulatory/auditory a n d visuo-spatial r e s o u r c e s , but more of the latter. ii  T a b l e of Content Abstract T a b l e of Content List of T a b l e s List of Figures Acknowledgements Introduction Experiment 1 Method Participants Apparatus Materials T o n e Discrimination T a s k PDA Tasks Neuropsychological Tests Design Procedures Results Data Preparation PDA Tasks T o n e Discrimination T a s k Discussion Experiment 2 Method Participants Apparatus T o n e Discrimination T a s k PDA Tasks Design Procedures Results Data Preparation PDA Tasks T o n e Discrimination T a s k Discussion Experiment 3 Methods Participants Materials Input T a s k s Letter T r a c i n g T a s k Sentence Decision Task Output T a s k s Pointing Tapping Saying Neuropsychological Tests Design  '. ;  ii iii v vi vii 1 10 10 10 10 11 11 12 13 13 14 15 15 17 18 20 23 24 24 24 24 25 26 26 27 27 28 30 33 36 37 37 37 38 38 39 40 40 40 40 40 41 iii  Procedures Results Data Preparation Input a n d Output T a s k s Discussion Experiment 4 Participants Apparatus Input T a s k s Output T a s k s P D A Tasks Design Procedures Results Data Preparation P D A Tasks Secondary Tasks Discussion General Discussion Conclusion References  41 4  2  4  2  4  3  4  4  4  7  4  7  4  7  4  7  4  7  4  8  4  4  5  ^ ^ 0  50 5  1  55 56 59 67 8  7  iv  List of T a b l e s T a b l e 1 T h e n u m b e r of Optimal S t e p s / P r e s s e s for e a c h P D A T a s k a s a n Indicator of T a s k Difficulty 68 T a b l e 2 P e r c e n t a g e of Correct, Incorrect, and Adjusted Identifications in the T o n e Discrimination T a s k a c r o s s C o n d i t i o n s  69  T a b l e 3 T h e N u m b e r of S t e p s / P r e s s e s R e q u i r e d by e a c h P D A T a s k a c r o s s T o n e Discrimination T a s k Difficulty  70  T a b l e 4 P e r c e n t a g e of Correct, Incorrect, and Adjusted Identifications in the T o n e Discrimination T a s k a c r o s s T a s k Conditions and T o n e Discrimination Difficulty  71  T a b l e 5 T h e n u m b e r of S t e p s / P r e s s e s R e q u i r e d by e a c h P D A T a s k A c r o s s Conditions 72  v  List of F i g u r e s Figure 1. Picture of the d e v i c e u s e d for the experiment  73  Figure 2. R e s p o n s e time (mean of median) for correct identification of target tones a c r o s s conditions  74  Figure 3. P e r c e n t a g e of errors in data entry and navigation t a s k s a s a function of tone discrimination difficulty 75 Figure 4. R e s p o n s e time (mean of m e d i a n s ) of correct identifications in the tone discrimination task a s a function of tone discrimination difficulty a n d task c o n d i t i o n s . . . 76 Figure 5. Stimuli for the practice trials of the letter tracing task  77  Figure 6. Stimuli for the test trials of the letter tracing task  78  Figure 7. Illustration of a trial of the letter tracing task with top/bottom instructions  79  Figure 8. Illustration of a trial of the letter tracing task with outside instructions  80  Figure 9. Image of s t a g g e r e d Y a n d N of the output task (pointing)  81  Figure 10. M e a n c o m p l e t i o n time a s a function of input task a n d output task  82  Figure 11. P e r c e n t a g e of P D A task errors a s a function of input task, output task, and P D A task type 83 Figure 12. T y p i n g s p e e d (words per minute) in data entry t a s k s a s a function of input task, and output task 84 Figure 13. C o m p l e t i o n time in navigation tasks a s a function of input task, a n d output task 85 Figure 14. C o m p l e t i o n time of the concurrent tasks a s a function of input task, output task, a n d P D A task type 86  vi  Acknowledgements M a n y p e o p l e h a v e helped m e to a c c o m p l i s h this work. I a m d e e p l y grateful to my supervisor, P e t e r Graf, for his time, patience, g u i d a n c e throughout the entire p r o c e s s . I would like to thank his v a l u a b l e c o m m e n t s on my writing, constant e n c o u r a g e m e n t to present my work at v a r i o u s c o n f e r e n c e s , a n d mentorship in guiding m e in my work. H e h a s taught m e , a n d continues to t e a c h m e , how to u s e w o r d s carefully, how to e x p r e s s myself clearly, a n d how to o r g a n i z e my thoughts logically. I would like to thank my committee m e m b e r s , J o a n n a M c G r e n e r e a n d R o n R e n s i n k , for their thoughtful considerations of my thesis a n d for lending their time and expertise to help m e improve it. I'd like to thank G e r y F u n g a n d M a g g i e S e k h o n for their careful a n d d e d i c a t e d data entry. I a l s o want to thank R a l p h Hakstian a n d J e r e m y B i e s a n z for t e a c h i n g m e the statistics knowledge that I n e e d e d in order to perform the relevant a n a l y s e s for this thesis work. I would to thank my friend a n d lab mate, C a r r i e Cuttler, for helping me with my E n g l i s h , providing v a l u a b l e f e e d b a c k , and sharing her e x p e r i e n c e s about a c a d e m i c life with m e . I want to thank my lab mate a n d friend, J e s s G a o , for sharing her knowledge about conducting e x p e r i m e n t s with m e , a n d providing m e a d v i c e in handling living related matters. I would a l s o like to thank Daniel S i u , my lab mate a n d friend, for cheering m e up w h e n I w a s feeling upset, for continually urging m e to persist, for showing constant c a r e for my well-being, a n d for t e a c h i n g m e how to b e c o m e a better p e r s o n . I would like to thank L y n n Fontanilla for listening to m e rambling on about this project for two y e a r s . I a l s o want to thank all of my family in H o n g K o n g a n d V a n c o u v e r , for providing g e n e r o u s help to m e . I a l s o want to thank e v e r y o n e in my family for their love a n d support. I e s p e c i a l l y thank my m o m and d a d , for their unconditional support during vii  t h e s e two y e a r s , for their understanding w h e n I didn't regularly s p e n d time with them. Finally, I would like to thank my sister, Y u k i e L i , for bringing m e c o u n t l e s s m o m e n t s of joy w h e n w e s p e n t time together, a n d for assisting m e with the h o u s e h o l d c h o r e s w h e n I got too busy. I a l s o would like to thank the Elizabeth Y o u n g L a c e y foundation, a n d my supervisor, P e t e r Graf, for believing in my potential to financially support m e .  1 Introduction P e r s o n a l Digital A s s i s t a n t s ( P D A s ) are mobile d e v i c e s that are e q u i p p e d with various applications a n d u s e d in a wide range of environments. F o r e x a m p l e , t h e s e d e v i c e s are u s e d to look up route information to navigate around a city ( G o o d m a n , G r a y , K h a m m a m p a d & Brewster, 2004), to look up a n d a c c e s s m e d i c a l reference information ( E m b i , 2001), to write a n d s e n d email m e s s a g e s , a n d to store contact information (e.g., a p h o n e number). S o m e e x a m p l e s of environments in w h i c h t h e s e applications are u s e d include a b u s y sidewalk, a quiet r o o m , a n d a bright, s u n n y d a y o n the b e a c h . T h e nature of the environments in which P D A s are u s e d a n d the applications for which P D A s are u s e d differ widely. O n e of the most important variables that distinguish between the various e n v i r o n m e n t s a n d applications is the attentional d e m a n d s . Environments a n d applications differ with respect to their attentional d e m a n d s . F o r e x a m p l e , a b u s y street is more attention d e m a n d i n g than a quiet room. Looking up a stored d o c u m e n t in a directory is more attention d e m a n d i n g than p r e s s i n g a button to turn off the d e v i c e . T h e overall goal of this thesis w a s to learn about the interactions of the attentional d e m a n d s b e t w e e n various environments a n d applications. T h e r e are s e v e r a l p o s s i b l e combinations of e n v i r o n m e n t s a n d applications in relation to their level of attentional d e m a n d s . First, both the environment and application c a n require little or no attention. O n e s u c h e x a m p l e c a n be recording a simple voice m e s s a g e on a d e v i c e while walking on a quiet street. T h e s e c o n d combination o c c u r s w h e n either the environment or the P D A application is attention d e m a n d i n g . O n e of the e x a m p l e s is trying to type a formal email (i.e., high in attention d e m a n d ) in a quiet room (i.e., low attention d e m a n d ) . T h e f o c u s of this thesis is to explore the third combination,  1  w h e n both the environment a n d application are highly attention d e m a n d i n g , for e x a m p l e , typing a formal email while walking on a b u s y sidewalk. O n e of the factors that determine the level of attentional d e m a n d s of an activity is the extent to w h i c h cognitive control is required to e x e c u t e that activity. S c h n e i d e r and Shriffin (1977) distinguished between two types of cognitive p r o c e s s e s , automatic a n d controlled, that varies o n the amount of attentional d e m a n d s . A u t o m a t i c p r o c e s s e s require little or no attention. T h i s is b e c a u s e the execution of the activity that relies on automatic p r o c e s s e s d r a w s o n previously learnt r e s p o n s e s . A s a result, automatic p r o c e s s e s c a n operate in combination with other activities that are attention d e m a n d i n g . Activities that rely o n automatic p r o c e s s i n g require extensive training a n d practice. In contrast, controlled p r o c e s s e s are initiated through effort a n d cognitive control. D u e to the fact that t h e s e p r o c e s s e s require substantial attention, they will interfere with other activities which a l s o require controlled p r o c e s s i n g . T h e interference o b s e r v e d while combining activities that are high in attentional d e m a n d s points to a g e n e r a l limited capacity in attentional r e s o u r c e s . T w o different c l a s s e s of attention theories h a v e b e e n p r o p o s e d to explain v a r i a n c e in interference during multi-tasking: S i n g l e r e s o u r c e theories ( K a h n e m a n , 1973) a n d multiple resource theories ( P a r a s u r a m a n & D a v i e s , 1984). S i n g l e r e s o u r c e theories p r o p o s e that there is only o n e general r e s e r v e of attention that c a n be allocated a m o n g s t various concurrent t a s k s or activities. T h e extent of interference will d e p e n d in part on the load which e a c h of the activities i m p o s e s a n d the allocation of attention a m o n g the activities (Moray, 1967). A s the primary task d e m a n d s more of t h e s e r e s o u r c e s (i.e., b e c o m e s more difficult) f e w e r are a v a i l a b l e for a concurrent or s e c o n d a r y task, a n d performance on the latter task deteriorates accordingly. Primary-task workload w o u l d be inversely reflected  2  in s e c o n d a r y - t a s k p e r f o r m a n c e , d e p e n d i n g on the allocation of attention toward the primary activity (Moray, 1967). T h e multiple r e s o u r c e theory s u g g e s t s that there is more than o n e resource for p r o c e s s i n g information. O n e of the most well-known multiple r e s o u r c e theories w a s formulated by B a d d e l e y a n d Hitch (1974). T h e y p r o p o s e d a tripartite s y s t e m that involves a n attentional controller (central executive) a s s i s t e d by two s l a v e s y s t e m s : T h e visuo-spatial s k e t c h p a d a n d the phonological loop. T h e central executive is responsible for coordinating information from the s l a v e s y s t e m s . T h e central executive is a s s u m e d to function like a n attentional s y s t e m that selects a n d o p e r a t e control p r o c e s s e s and strategies. T h e visuo-spatial s k e t c h p a d is u s e d to hold a n d manipulate visual i m a g e s . T h e phonological loop is u s e d to hold a n d manipulate s p e e c h - r e l a t e d information. A c c o r d i n g to this theory, two activities that require the s a m e types of attention would s h o w task interference. That is, there should be o b s e r v a b l e d e c r e m e n t s in performance on an activity e x e c u t e d singly c o m p a r e d to tending that activity with a s e c o n d activity that a l s o requires the s a m e r e s o u r c e s . Interference b e t w e e n the environment and applications c a n a l s o arise w h e n there is competition for the s a m e sensory/perceptual p r o c e s s e s . A n e x a m p l e includes trying to find a p h o n e n u m b e r (i.e., application) while driving (i.e., environment). Both activities d e m a n d the visual modality a n d thus it is n e c e s s a r y to switch between the two activities in order to h a n d l e both t a s k s concurrently. In other w o r d s , the efficiency of performing both activities is limited at the s p e e d in which vision c a n be switched between the two activities. T h e limits of attending to both activities are restricted at the visual level of p r o c e s s i n g . T h e r e is a large a r e a of r e s e a r c h that investigates the interference that o c c u r s d u e to competition for the s a m e s e n s o r y / p e r c e p t u a l p r o c e s s e s  3  (Broadbent 1957, 1958). H o w e v e r , this a r e a is not of interest to the present thesis and will not be d i s c u s s e d further. Previous  Research  Prior r e s e a r c h on attention and technology u s e h a s generally f o c u s e d on exploring the effects of individual differences in attention on technology usability. For e x a m p l e , d e s i g n guidelines are generally targeted towards a c c o m m o d a t i n g individuals with r e d u c e d attentional capacity, s u c h a s older adults (Connelly & H a s h e r , 1993; Kotary & Hoyer, 1995). Morris a n d V e n k a t e s h (2000) noted that large a m o u n t s of information are usually presented on small displays (e.g., mobile d e v i c e s ) , a n d that could be problematic for older adults w h o have difficulties in handling a lot of information at the s a m e time a n d sorting out task relevant information. T h e y s u g g e s t e d that interfaces with r e d u c e d information content m a k e it e a s i e r to f o c u s attention on relevant information a n d r e d u c e the time spent on information s e a r c h . A i d in focusing attention c a n be provided by structuring the information, providing spatial a n d temporal c u e s , and manipulating the s c r e e n layout. G u i d e l i n e s of interface d e s i g n h a v e a l s o included r e c o m m e n d a t i o n s to e x c l u d e graphic details that m a y be decorative to prevent distraction (Hawthorne, 2000). Individual differences in certain cognitive abilities h a v e b e e n s h o w n to be related to information s e a r c h performance on a wide range of t e c h n o l o g i e s . S e v e r a l studies have found that individuals with lower spatial ability a n d poorer v o c a b u l a r y skills take longer to retrieve information from a hierarchical d a t a b a s e on a c o m p u t e r (Freudenthal, 2 0 0 1 ; V i n c e n t e , H a y e s & Williges, 1987). T h i s effect d u e to spatial ability w a s prominent e v e n after taking into a c c o u n t prior e x p e r i e n c e with t e c h n o l o g y (Vincente, H a y e s & Williges, 1987). Individuals with poorer spatial ability performed less efficient s e a r c h e s on a cell phone (Ziefle & B a y , 2004). O n s e a r c h i n g for information from the W o r l d W i d e 4  W e b , individuals with poorer spatial ability took longer to find the relevant information (Dahlback, H o o k & Sjolinder, 1996). L o w e r mental rotation, verbal a n d visual m e m o r y performance w a s linked to greater time spent on the task in virtual reality navigation (Moffat, Z o n d e r m a n & R e s n i c k , 2001). Data entry p e r f o r m a n c e o n a full-sized keyboard h a s b e e n linked with basic cognitive abilities in a study by C z a j a a n d Sharit (1998). A g e , p r o c e s s i n g s p e e d , motor skills, visuo-spatial skills a n d prior computer e x p e r i e n c e h a v e b e e n found to have an impact o n entering d a t a into records or s e a r c h fields. A m o n g t h e s e factors, visuo-motor skills a n d m e m o r y predicted the number of typing errors a b o v e a n d b e y o n d prior e x p e r i e n c e with c o m p u t e r s . In a recent study (Li a n d Graf, 2007), certain cognitive abilities w e r e found to predict data entry p e r f o r m a n c e on a P D A . A m o n g s e n s o r y abilities, e p i s o d i c memory, perceptuo-motor skills, a n d verbal intelligence, w e found that s e n s o r y abilities and episodic m e m o r y w e r e the stronger predictors for different t y p e s of data entry errors o n a P D A . T h e finding that verbal intelligence had no predictive power is not surprising in view of the fact that n o n e of the data entry t a s k s w e r e d e s i g n e d to c h a l l e n g e verbal skills or to require e x t e n s i v e l a n g u a g e p r o c e s s i n g . Objectives and Motivations T h e motivation for this r e s e a r c h w a s to learn more about the factors that influence the usability of P D A s in order to i n c r e a s e the usability of t h e s e d e v i c e s . T h e majority of r e s e a r c h a n d d e s i g n guidelines have f o c u s e d on providing support for individuals with poorer cognitive abilities. H o w e v e r , the usability of technologies c a n be c o m p r o m i s e d e v e n for individuals with relatively better cognitive abilities in certain situations. If the application is inherently very attention d e m a n d i n g , then usability is reduced w h e n t h e s e applications are u s e d in environments that are a l s o attention 5  d e m a n d i n g , for e x a m p l e , recording a c o m p l e x v o i c e m e s s a g e while driving in busy traffic. M o r e o v e r , if both the environment and application d e m a n d the s a m e type of attention, then usability c a n a l s o be c o m p r o m i s e d . A s a first step to understanding the interference that might be p r o d u c e d in t h e s e situations, o n e of the objectives of this thesis is to learn more about whether certain P D A t a s k s are m o r e attention d e m a n d i n g than others, a n d about the type of attention that they require. T h e s e c o n d motivation for this r e s e a r c h w a s to e x a m i n e the relationship between attention a n d P D A usability in order to guide d e s i g n specifications for t h e s e d e v i c e s to be more suitable for the various environmental d e m a n d s . W h i l e it h a s certainly b e e n inferred that attention plays a crucial role in the usability of t e c h n o l o g y (Hawthorn, 2000), there h a v e b e e n few studies that empirically d e m o n s t r a t e d a link between attention a n d usability. In addition, while there is a plethora of d e s i g n guidelines on designing w e b s i t e s , cell p h o n e m e n u s , a n d interfaces of v a r i o u s software applications and computer s y s t e m s , the guidelines m a y not be a p p l i c a b l e to P D A s . P D A s generally have different s i z e d s c r e e n s a n d rely on a different interaction t e c h n i q u e (i.e., t o u c h s c r e e n using stylus). T h u s , I believe that is a l s o important to generate empirical data that s e r v e s a s a start for basing design guidelines for P D A s . Contributions T h i s type of r e s e a r c h s e r v e s to identify whether future r e s e a r c h n e e d s to be f o c u s e d on reducing the attentional d e m a n d s of certain t y p e s of P D A t a s k s in order to m a x i m i z e the effective a n d efficient u s e of t h e s e d e v i c e s . O n e of the limitations of previous studies is that they often only report either the completion time (an index of efficiency), or n u m b e r of errors (an index of efficacy). T h u s , it is difficult to ascertain whether the individuals e x p e r i e n c e d a s p e e d - a c c u r a c y trade-off. In addition, the studies that reported the n u m b e r of committed errors are e x p r e s s e d a s absolute v a l u e s . A s a 6  result, it is difficult to interpret whether the error p r e s s e s w e r e c o n s i d e r e d high or low in relation to the total n u m b e r of p r e s s e s . M o r e o v e r , the criteria u s e d to classify errors were unclear. T h e e x p e r i m e n t s in this thesis a d d r e s s e d the three limitations mentioned earlier. T h e e x p e r i m e n t s u s e d clearly d e v e l o p e d criteria to c a t e g o r i z e d errors, u s e d standardized m e t h o d s to calculate the d a t a , a n d reported i n d e x e s of both efficiency a n d effectiveness. T h i s r e s e a r c h d e v e l o p e d and validated a dual-task m e t h o d o l o g y to a s s e s s the attentional d e m a n d s of technology u s e . W h i l e this methodology h a s b e e n u s e d in a variety of h u m a n factor studies (see W i c k e n s , 1992 for a review) a n d m e m o r y studies (Craik, G o v o n i , N a v e h - B e n j a m i n & A n d e r s o n , 1996; F e r n a n d e s & M o s c o v i t c h , 2 0 0 0 ; N a v e h - B e n j a m i n , C r a i k , G u e z , Dori, 1998), this method h a s not yet b e e n applied to specifically a s s e s s the attentional d e m a n d s of P D A t a s k s . T h e d e s i g n of the s e c o n d a r y task must meet s e v e r a l criteria. First, the s e c o n d a r y task must be d e s i g n e d to a s s e s s interference p r o d u c e d by the attentional d e m a n d s of the P D A t a s k s , a n d not interference produced by competition of the s a m e perceptual p r o c e s s e s of the P D A t a s k s . S e c o n d , the s e c o n d a r y task must include m e a s u r a b l e performance v a r i a b l e s . O n c e validated, this method c a n a l s o be u s e d to a s s e s s the attentional d e m a n d s of other technological d e v i c e s , s u c h a s cell p h o n e s , m p 3 players, and applications o n p e r s o n a l c o m p u t e r s . Overview T h e overall g o a l of this thesis is to understand the attentional d e m a n d s of P D A t a s k s . W h i l e there are m a n y applications that c a n be u s e d on a P D A , the majority c a n be classified in o n e of two types of t a s k s : Navigation a n d data entry. Navigation refers to locating a certain file, folder or d e v i c e information through the m e n u options. Data  7  entry refers to entering d a t a (i.e., a specific p h r a s e or n u m b e r s ) via a t o u c h - s c r e e n keyboard using a stylus. T h e dual-task methodology w a s u s e d a s the g e n e r a l set-up for m e a s u r i n g the attentional d e m a n d s of performing P D A t a s k s . T h e methodology involves having an individual perform two t a s k s concurrently (i.e., divided attention condition), a n d to m e a s u r e task interference relative to single-task p e r f o r m a n c e (i.e., full attention condition). In my e x p e r i m e n t s , the P D A t a s k s w e r e a l w a y s d e s i g n a t e d a s the primary task. Therefore, c h a n g e s in s e c o n d a r y task performance w e r e attributed to the r e d u c e d availability of attention d u e to allocation of attentional r e s o u r c e s to the P D A t a s k s . F o r experiment 1 a n d 2, I c h o s e tone discrimination a s the s e c o n d a r y task s i n c e this task h a s b e e n s h o w n to involve the central executive ( K l a u e r & S t e g m a i e r , 1997). T h e s e c o n d r e a s o n is that this task w a s d e s i g n e d to avoid the s a m e perceptual p r o c e s s e s u s e d by the P D A t a s k s (i.e., auditory a n d v o c a l for tone discrimination; motor and vision for P D A t a s k s ) . T h i s arrangement e n s u r e d that the tone discrimination task a s s e s s e d the attentional d e m a n d s of P D A t a s k s , a s o p p o s e d to interference produced by competition for the s a m e modalities. Third, the tone discrimination task offered o b s e r v a b l e p e r f o r m a n c e variables which could be m e a s u r e d objectively, which allowed c o m p a r i s o n s of any c h a n g e s in performance w h e n tone discrimination w a s performed with the P D A t a s k s . I d e s i g n e d a n d c o n d u c t e d two experiments to explore w h e t h e r data entry a n d navigation t a s k s require different a m o u n t s of attention. In E x p e r i m e n t 1, the s e c o n d a r y objective w a s to a d a p t the dual-task methodology to explore the attentional d e m a n d s of the P D A t a s k s . Participants w e r e a s k e d to first perform the tone discrimination task a l o n e to get a b a s e l i n e a s s e s s m e n t , followed by performing a s e r i e s of navigation or data entry t a s k s concurrently with the tone discrimination task. 8  Following up o n the findings from Experiment 1, E x p e r i m e n t 2 w a s d e s i g n e d to determine w h e t h e r the results obtained in Experiment 1 w e r e d u e to attentional d e m a n d s or d u e to the difficulty of switching between the tone discrimination task and P D A t a s k s . Participants first completed a n e a s y a n d hard v e r s i o n of the tone discrimination task in the b a s e l i n e condition. In the test conditions, participants completed the e a s y a n d hard version of the tone discrimination task with either a set of data entry a n d navigation t a s k s on the P D A . E x p e r i m e n t 3 a n d 4 w e r e d e s i g n e d and c o n d u c t e d to explore whether performing the data entry a n d navigation t a s k s require different types of attention. T h e primary objective of E x p e r i m e n t 3 w a s to confirm that a method d e v e l o p e d by B r o o k s (1968) is valid a n d reliable for revealing the types of attention, specifically visuo-spatial a n d auditory/articulatory attention. T h e s a m e t a s k s , a task that d r a w s on visuo-spatial r e s o u r c e s a n d a task that requires articulatory/auditory r e s o u r c e s , d e s c r i b e d in the original study w e r e u s e d . F o r E x p e r i m e n t 4 , the method validated in E x p e r i m e n t 3 w a s e m p l o y e d to a s s e s s the types of attention required by the P D A tasks. Participants performed concurrently either a navigation or d a t a entry task with o n e of the two t a s k s that require different types of attention d e s c r i b e d in Experiment 3.  9  Experiment 1 T h e primary objective of this study w a s to explore the attentional d e m a n d s of two P D A task types: Navigation a n d data entry. A dual-task methodology w a s u s e d to a s s e s s the attentional d e m a n d s of e a c h type of task. W h i l e the dual-task methodology has b e e n u s e d s u c c e s s f u l l y in other a r e a s of r e s e a r c h , it h a s b e e n never b e e n e m p l o y e d for a s s e s s i n g the attentional d e m a n d s of P D A t a s k s . T h u s , a n additional objective of the present study w a s to adapt the dual-task m e t h o d o l o g y to the exploration of the attentional d e m a n d s of P D A t a s k s . Method Participants Twenty-six undergraduate students were recruited through the subject pool in the p s y c h o l o g y department at the University of British C o l u m b i a . T h e y w e r e c o m p e n s a t e d with o n e c o u r s e credit in return for their participation. T h e experiment w a s c o n d u c t e d with the approval of the University of British C o l u m b i a behavioral ethics review board. Apparatus A n unmodified H e w l e t t - P a c k a r d i P A Q rx3715 h a n d h e l d c o m p u t e r w a s u s e d for this experiment [see Figure 1]. T h i s d e v i c e has a color s c r e e n w h i c h is 2.26 inches wide a n d 3.02 i n c h e s high. A s s h o w n in Figure 1, five hardware buttons are positioned below the s c r e e n . T h e button in the middle is a navigation key. T h e four other buttons are d e s i g n e d for a c c e s s i n g different applications a n d P D A status information. T o interact with the d e v i c e , u s e r s either p r e s s t h e s e buttons or u s e a stylus to select icons or m e n u options on the s c r e e n . D a t a entry is d o n e via a touch s c r e e n Q W E R T Y keyboard using a stylus. O n this s c r e e n , e a c h letter, digit or s y m b o l h a s a 'target a r e a ' (i.e. the a r e a for selecting e a c h letter) that m e a s u r e s 4 m m in width a n d 3 m m in height.  10  Figure 1 Materials T h e stimuli for the tone discrimination task w e r e pure t o n e s , e a c h exactly 100 m s in duration. O n e tone, herein called the standard tone, had a f r e q u e n c y of 4 0 0 0 H z . T h e other tones required for this task, called odd or target t o n e s , h a d f r e q u e n c i e s of 4 0 2 0 H z , 4 0 4 0 H z , 4 0 6 0 H z , 4 0 8 0 H z , 4 1 0 0 H z , 4 1 2 0 H z , 4 1 4 0 H z , 4 1 6 0 H z or 4 1 8 0 H z . All tones were created using A u d a c i t y v.1.2.6, a freeware C r o s s - P l a t f o r m S o u n d Editor ( M a z z o n i & D a n n e n b e r g , 2000). E a c h tone w a s stored a s a .wav file, with single c h a n n e l 16-bit P C M c o d i n g at a sampling rate of 44.1 k H z . Tone Discrimination Task Stimulus presentation a n d r e s p o n s e recording for the tone discrimination task were controlled by a P C , using the E P r i m e v. 1.0 software ( P s y c h o l o g y Software T o o l s Inc., Pittsburg, P A ) . Participants wore h e a d p h o n e s to e n s u r e controlled presentation of the tones. T h e v o l u m e of the t o n e s w a s set at a level w h i c h e a c h individual c o n s i d e r e d to be "comfortable". F o r the tone discrimination task, participants listened to a s e r i e s of standard tones interspersed with target t o n e s . I instructed participants to s a y the word 'fruit' into the m i c r o p h o n e e a c h time they heard a target tone (i.e., a tone higher in pitch than the standard tone). T h i s r e s p o n s e word (i.e., fruit) w a s c h o s e n to e n s u r e that the microphone captured the onset of the v o c a l r e s p o n s e . Participants w e r e instructed to m a k e their r e s p o n s e s a s accurately a n d a s quickly a s p o s s i b l e . T h e tone discrimination task c o n s i s t e d of nine b l o c k s , e a c h with 150 trials. T h e target tones varied a c r o s s blocks while the standard tone r e m a i n e d constant. During e a c h trial, a tone w a s p r e s e n t e d followed by a random inter-stimulus interval (ISI) of 500 m s , 1000 m s , 1500 m s , 2 0 0 0 m s , 2 5 0 0 m s or 3 0 0 0 m s (the ISI following a target tone 11  w a s a l w a y s 1500 m s in duration to e n s u r e an a d e q u a t e a m o u n t of time for responding). T h e first three trials in e a c h block a l w a y s involved the presentation of a standard tone in order to "habituate" participants to this s o u n d . In the remaining 147 trials, participants were presented with either a standard or target tone. O n e a c h set of thirteen trials, two trials w e r e randomly s e l e c t e d to present a target tone. P D A Tasks S i x c o m m o n P D A t a s k s w e r e s e l e c t e d . T h r e e t a s k s required s e a r c h i n g through the m e n u layers to find information (check the battery, retrieve appointments and find a picture), a n d 3 t a s k s required entering data (enter contact information, enter e x p e n s e information, a n d m a k e a n appointment). E a c h of t h e s e t a s k s c a n be completed in a n u m b e r of different w a y s . T a b l e 1 s h o w s the n u m b e r of s t e p s required for completing e a c h task in the most efficient or optimal manner. Table 1 Check the battery. T h e instructions for this task directed participants to find the current status of the P D A battery a n d to report the remaining battery c h a r g e . Retrieve appointments. F o r this task, participants w e r e required to find and report to the experimenter all appointments s c h e d u l e d for 7 w e e k s a w a y from the current date. Find a picture. Participants were instructed to find a picture of a green door in the p e r s o n a l folder. Enter contact information. F o r this task, participants w e r e required to find the contacts function, a n d to enter contact information for a laboratory, including the n a m e , the complete a d d r e s s , a s well a s the p h o n e n u m b e r a n d the e m a i l a d d r e s s of that laboratory.  12  Enter expense information. Participants w e r e required to find the E x c e l workbook a n d enter a s e r i e s of n u m b e r s into d e s i g n a t e d cells. Make an appointment. T h i s task required finding the date 6 w e e k s a w a y from the current date in the c a l e n d a r , entering a restaurant n a m e for a n appointment at noontime, a n d setting a reminder to go off one hour prior to this event. Neuropsychological Tests A n e u r o p s y c h o l o g i c a l test battery w a s e m p l o y e d to a s s e s s participants' cognitive abilities. T h e battery w a s c o m p r i s e d of four s t a n d a r d i z e d tests: the Digit S y m b o l Substitution T e s t ( W e c h s l e r , 1981), the North A m e r i c a n Adult R e a d i n g T e s t (Blair & S p r e e n , 1989), the R e v e r s e Digit S p a n T e s t ( W e c h s l e r , 1981), a n d the Trail M a k i n g Test (Reitan, 1992). I administered e a c h n e u r o p s y c h o l o g i c a l test a c c o r d i n g to the instructions in the published m a n u a l s . T h e results of t h e s e tests are not directly pertinent to the objectives of the present project and thus will not be reported or d i s c u s s e d here. Design T h i s experiment included a baseline condition a n d two critical test conditions identified, respectively, a s the data entry a n d navigation condition. In the baseline condition, participants c o m p l e t e d the tone discrimination task a l o n e , while in the critical test conditions, they c o m p l e t e d this task concurrently with a P D A task. T h e baseline condition w a s required in order to find a difficulty level w h e r e tone discrimination a c c u r a c y w a s approximately 8 0 % for e a c h participant. T h i s a c c u r a c y level w a s s e l e c t e d b e c a u s e it reflects p e r f o r m a n c e that is off the ceiling, while leaving sufficient d o w n - s i d e room for revealing the additional resource d e m a n d s of the concurrent P D A t a s k s which had to be c o m p l e t e d in the data entry a n d navigation condition. E a c h participant completed the s a m e set of P D A t a s k s , which are listed in T a b l e 1. 13  Procedures I tested participants individually in a s e s s i o n that lasted approximately 60 minutes. U p o n obtaining their written c o n s e n t , I administered the t a s k s in the order d e s c r i b e d below. E a c h participant first completed the tone discrimination task a l o n e in the baseline condition in order to find a frequency difference between the standard a n d target tone at which a level of a c c u r a c y of approximately 8 0 % would be a c h i e v e d . In order to find this level, I u s e d a calibration procedure in which the f r e q u e n c y of the target tone w a s reduced by 2 0 H z (i.e., the difference between the target tone a n d the standard tone w a s d e c r e a s e d ) a c r o s s s u c c e s s i v e blocks of trials. Specifically, for the first block of trials, the target tone f r e q u e n c y w a s 4 1 0 0 H z . If p e r f o r m a n c e a c c u r a c y w a s a b o v e 8 0 % after 150 trials, I r e d u c e d the target tone frequency by 2 0 H z for the next block of 150 trials. I continued with this calibration procedure until the participant's performance w a s approximately at 8 0 % . In the next p h a s e of the experiment, participants c o m p l e t e d the tone discrimination task together with the P D A t a s k s in the order listed in T a b l e 1.1 instructed participants to f o c u s on completing the P D A t a s k s accurately a n d quickly, but to respond to the target t o n e s w h e n e v e r possible. F o r e a c h of the P D A t a s k s , I explained to participants about the g o a l of the task. F o r the navigation t a s k s , participants were given written instructions about the goal of the task. F o r the data entry t a s k s , participants w e r e provided with the to-be entered information in written form. Participants w e r e free to refer to the instruction sheet at a n y time during the task. At a n y time in the c o u r s e of a n y of the t a s k s , participants w e r e permitted to a s k for help, for hints or information about how to p r o c e e d .  14  T h e f r e q u e n c y difference between the standard a n d target tone which w a s obtained for e a c h subject in the baseline condition w a s u s e d for the tone discrimination task w h e n it had to be performed in conjunction with o n e of the data entry or navigation t a s k s in the critical test conditions. I started the tone discrimination task w h e n participants b e g a n e a c h P D A task a n d terminated the task a s s o o n a s the P D A task was completed. A Hitachi D Z - M V 3 8 0 A digital video c a m e r a w a s u s e d to create a complete record of participants' b u t t o n - p r e s s e s a n d stylus interactions with the P D A from the start (i.e., turning the P D A on) to the e n d (i.e., turning the P D A off) of e a c h P D A task for offline coding. I started the v i d e o recording immediately before participants turned the P D A on a n d s t o p p e d the v i d e o recording immediately after participants c o m p l e t e d the task and turned the P D A off. Following the completion of the P D A t a s k s , I administered the battery of n e u r o p s y c h o l o g i c a l tests. After the last n e u r o p s y c h o l o g i c a l test w a s c o m p l e t e d , participants w e r e given a verbal debriefing, a s well a s a debriefing form, and c o u r s e credit. Results Data Preparation F o r the P D A t a s k s , I d e v e l o p e d a detailed m a n u a l with step-by-step instructions for scoring e a c h interaction (e.g., button-press, stylus-click) with the P D A , a s well a s for scoring participant-experimenter interactions (e.g., requests for help). T h e manual w a s d e v e l o p e d b a s e d o n the guidelines a n d definitions from a m a n u a l in a previous usability study (Graf & L i , 2007). F o r the m a n u a l in the previous study, a n iterative method w a s u s e d for d e v e l o p i n g the s c o r i n g m a n u a l , alternating b e t w e e n writing scoring instructions a n d applying t h o s e instructions, until the m a n u a l could be u s e d reliably by o n e other 15  coder. T w o independent c o d e r s s c o r e d the complete video record of 10 different subjects. T h e reliability w a s .80 a n d a b o v e a c r o s s the 9 different P D A t a s k s . Participants' p e r f o r m a n c e of the P D A t a s k s w a s c o d e d using the video records. I w a t c h e d the v i d e o s that captured participants' interaction with the P D A , a n d for e a c h task I counted the n u m b e r of p r e s s e s , a s well a s recorded the amount of time to complete e a c h task. F o r navigation t a s k s , a p r e s s w a s s c o r e d a s incorrect w h e n it displayed a n u n d e s i r e d s c r e e n (i.e., did not lead towards the completion of the task) or w h e n it p r o d u c e d no c h a n g e in the s c r e e n . Correct p r e s s e s yielded the display of a desired s c r e e n , o n e that w a s required to progress towards completing the task. C o m p l e t i o n time for navigation t a s k s w a s calculated by the a m o u n t of time e l a p s e d from the start to the e n d of the task. T h e start of a navigation task w a s defined by the first time the stylus t o u c h e d the s c r e e n ; the end w a s defined by the display of the target s c r e e n (i.e., the information to be found). I calculated data entry errors using a method d e v e l o p e d by W o b b r o c k a n d M y e r s (2006). Data entry error rate w a s e x p r e s s e d a s a function of uncorrected a n d corrected errors by the final entered data. T h e standardized metric w o r d s per minute ( W P M ) w a s u s e d a s a n indication of data entry s p e e d . I calculated data entry s p e e d by dividing the total n u m b e r of p r e s s e s by the completion time in minutes to c o m p u t e the characters per minute ( C P M ) metric. T h e n , I c o m p u t e d W P M by dividing C P M by five. T h e s e methods w e r e c h o s e n a s it allowed c o m p a r i s o n s a c r o s s studies using the s a m e metrics. T h e results from the tone discrimination task a n d P D A t a s k s w e r e s c r e e n e d for outliers, defined a s falling more than three standard deviations a w a y from the s a m p l e m e a n . O n e outlier w a s f o u n d . T h e outlier w a s r e p l a c e d with a non-outlying value, a n u m b e r that w a s three standard deviations a b o v e the s a m p l e m e a n .  16  F o r e a c h participant, I calculated the m e a n p e r c e n t a g e of correct and incorrect identifications of target t o n e s , adjusted identification of target t o n e s a n d the m e d i a n r e s p o n s e time ( R T ) for the correct and incorrect r e s p o n s e s in e a c h condition of the experiment (baseline, d a t a entry, navigation) for the tone discrimination task. A correct identification w a s s c o r e d w h e n a participant m a d e a r e s p o n s e to a target tone, while a n incorrect identification w a s s c o r e d w h e n a participant m a d e a r e s p o n s e to a standard tone. T h e adjusted identification s c o r e w a s c o m p u t e d by subtracting the percentage of incorrect identifications by the percentage of correct identifications. T h r e e participants did not m a k e a n y correct r e s p o n s e s on the tone discrimination task while they were concurrently performing either the data entry or navigation t a s k s . T h e data for t h e s e three participants w e r e e x c l u d e d from the a n a l y s i s . T h e a n a l y s i s w a s c o n d u c t e d with data from the remaining 2 3 participants. PDA Tasks T h e d e p e n d e n t m e a s u r e s for the P D A t a s k s w e r e the p e r c e n t a g e of correct p r e s s e s , the p e r c e n t a g e of errors in the data entry a n d navigation t a s k s , s p e e d of data entry, a n d the a m o u n t of time to complete navigation t a s k s . T h e a v e r a g e p e r c e n t a g e of correct p r e s s e s in navigation a c r o s s the t a s k s w a s 5 6 . 5 8 % ( S D = 10.90). O v e r a l l , 3 8 . 8 3 % ( S D = 14.16) of the total p r e s s e s w a s categorized a s incorrect in navigation. A m o n g the navigation t a s k s , participants m a d e the greatest p e r c e n t a g e of errors while trying to find the p a g e for entering contact information (M = 5 8 . 3 1 , SD = 21.53), followed by trying to find the battery (M = 4 7 . 2 7 , S D = 24.90), trying to find the correct date to m a k e a n appointment (M = 4 4 . 7 1 , S D = 28.62), trying to retrieve the appointment dates (M = 2 9 . 8 7 , S D = 25.58) and finding a picture {M = 3 6 . 9 7 , S D = 30.01). Finally, participants m a d e the least percentage of errors trying to find the E x c e l program to enter information (M = 15.83, S D = 22.19). 17  T h e a v e r a g e p e r c e n t a g e of correct p r e s s e s in navigation a c r o s s the tasks w a s 7 7 . 7 1 % ( S D = 5.71). Of the total p r e s s e s m a d e during data entry, 6 . 6 0 % ( S D = .03) were errors. In g e n e r a l , the p e r c e n t a g e of errors for e a c h d a t a entry task w a s low. Participants m a d e the s m a l l e s t percentage of errors while entering information in the E x c e l s h e e t (M = 4 . 8 0 , SD = 5.73), followed by entering contact information (M = 7.21, SD = 3.07), a n d entering appointment information (M = 7.80, SD = 3.00). A paired s a m p l e s f-test w a s c o n d u c t e d using the a v e r a g e p e r c e n t a g e of navigation a n d d a t a entry t a s k s errors. T h e results r e v e a l e d that participants m a d e a significantly greater p e r c e n t a g e of errors w h e n performing navigation t a s k s c o m p a r e d to data entry t a s k s , f (22) = 11.39, p < .001. A v e r a g e c o m p l e t i o n time for the navigation t a s k s w a s 3 2 . 1 5 s (SD = 14.43). Finding the battery (M = 4 8 . 3 0 , SD = 27.16) took the longest, followed by finding the contacts p a g e for entering information (M = 4 1 . 0 5 , S D = 33.09) a n d finding the correct date for entering appointment information (M = 4 1 . 6 5 , S D = 29.09). Finding the appointment date took 30.61 s e c o n d s ( S D = 29.78), followed by finding the picture (M = 23.04, S D = 21.40), a n d finding the E x c e l s h e e t (M = 8.22, S D = 6.84). M e a n data entry s p e e d for the data entry t a s k s w a s 11.31 W P M ( S D = 2.28). Data entry s p e e d w a s the quickest for entering appointment information (M = 14.93, S D = 4.43), followed by entering contact information (M = 10.08, S D = 4.85), and entering information in an E x c e l s h e e t (M = 8 . 9 1 , S D = 1.60). Tone Discrimination Task T h e p u r p o s e of this experiment w a s to explore how p e r f o r m a n c e c h a n g e d w h e n the tone discrimination task w a s performed alone v e r s u s in conjunction with a P D A task. T h e d e p e n d e n t m e a s u r e s for the tone discrimination task, in e a c h task condition, were  18  the p e r c e n t a g e of correct, incorrect, and adjusted identifications of target t o n e s , and the time required to m a k e correct identifications. T a b l e 2 s h o w s the m e a n percentage of correct, incorrect, a n d adjusted identifications of target t o n e s , a s well a s the 9 5 % c o n f i d e n c e intervals, for e a c h condition. C o m p a r e d to the B a s e l i n e condition, p e r f o r m a n c e w a s lower in both the Data Entry a n d Navigation condition, but this effect w a s greater in the Navigation condition. Participants m a d e a similar percentage of incorrect identifications in the B a s e l i n e and Navigation condition. Participants m a d e approximately 1/3 f e w e r incorrect identifications in the Data Entry condition. Table 2 In order to take into a c c o u n t the effect of differences in incorrect identifications on the pattern of correct identifications, the adjusted identifications w e r e explored in detail. T h e a v e r a g e v a l u e s of adjusted identifications for the b a s e l i n e , data entry, a n d navigation conditions followed the s a m e pattern a s correct identifications. T h e m e a n value in the d a t a entry a n d navigation condition w a s not e n c o m p a s s e d by the 9 5 % c o n f i d e n c e interval of the b a s e l i n e condition, indicating that p e r f o r m a n c e a c c u r a c y w a s significantly lower in both the data entry a n d navigation conditions c o m p a r e d to the baseline condition. Similarly, the 9 5 % confidence interval of the data entry condition d o e s not include the m e a n v a l u e of the navigation condition, indicating that a c c u r a c y w a s significantly lower than performance a c c u r a c y in the data entry condition. A large effect s i z e w a s found for the percentage of correct identifications a c r o s s conditions, / = 2.31. S i n c e the pattern of results did not c h a n g e e v e n w h e n taking into account the incorrect identifications d a t a , only the m e d i a n r e s p o n s e times for correct identifications were e x p l o r e d . Figure 2 s h o w s the r e s p o n s e time (mean of m e d i a n s ) for correct 19  identification of target t o n e s , a s well a s the 9 5 % c o n f i d e n c e intervals, in e a c h condition. T h e s u m m a r i z e d results revealed i n c r e a s e d r e s p o n s e times for both the data entry a n d navigation conditions c o m p a r e d to the baseline condition. T h e m e a n r e s p o n s e times in the data entry a n d navigation conditions w e r e not e n c o m p a s s e d by the 9 5 % confidence interval of the b a s e l i n e condition, indicating that r e s p o n s e time w a s significantly greater in the test conditions. R e s p o n s e times w e r e not significantly different a c r o s s the D a t a Entry a n d Navigation conditions. A large effect size w a s found for the r e s p o n s e times a c r o s s conditions, / = 0.96. Figure 2 Discussion F o r this experiment, I d e v e l o p e d a version of the dual-task methodology to explore the attentional d e m a n d s of navigation a n d data entry t a s k s . I had participants perform a tone discrimination task in the baseline condition in order to find a difficulty level that would yield a c c u r a c y performance at approximately 8 0 % . Next, participants performed the tone discrimination task with either a data entry or navigation task. P e r f o r m a n c e for both the data entry a n d navigation t a s k s w a s poorer than what w a s found in previous studies. In particular, data entry errors w e r e slightly greater a n d typing s p e e d w a s s l o w e r c o m p a r e d to studies w h e r e participants performed data entry using a Q W E R T Y k e y b o a r d on a P D A . Z h a a n d S e a r s (2001) reported 4 % (12.62 W P M ) and 5 % error rate (6.98 W P M ) for two data entry t a s k s . F l e e t w o o d et al. (2002) found that experts enter uncorrected text (i.e., w h e r e e r a s i n g errors w e r e not permitted) at a rate of 17.91 W P M a n d n o v i c e s enter at a rate of 15.38 W P M with a 2 % error rate for both g r o u p s . F o r navigation t a s k s , participants took longer to find the information a n d m a d e a greater p e r c e n t a g e of errors c o m p a r e d to the findings in a recent usability study with a P D A (Graf & L i , 2 0 0 7 ) . 20  T h e poorer P D A task performance found in this experiment is likely d u e to distraction of concurrently attending to the tone discrimination task. Attending to a s e c o n d task m a y h a v e distracted participants from performing the P D A t a s k s a s well a s they could w h e n they performed t h e s e P D A tasks a l o n e . H o w e v e r , the results obtained in this experiment w e r e only slightly poorer c o m p a r e d to findings obtained in previous studies (Graf & L i , 2 0 0 7 ; F l e e t w o o d et al., 2 0 0 2 ; Z h a & S e a r s , 2 0 0 1 ) w h e n full attention w a s available (i.e., w h e n the P D A t a s k s were c o m p l e t e d alone). T h e findings from this experiment s u g g e s t that participants f o c u s e d on completing the P D A t a s k s a s well a s possible. T h e results from the tone discrimination task are consistent with findings from previous s t u d i e s that a l s o found s e c o n d a r y task c o s t s w h e n participants were required to perform two t a s k s concurrently (e.g., Troyer, W i n o c u r , C r a i k & M o s c o v i t c h , 1999; A n d e r s o n , l i d a k a , C a b e z a , K a p u r , M c i n t o s h & C r a i k , 2000). T h e c o m p a r a b l e findings indicate that a dual-task methodology using tone discrimination is valid for a s s e s s i n g the attentional d e m a n d s of P D A t a s k s . S e c o n d a r y task c o s t s obtained in this study w e r e slightly larger than what w a s found in previous r e s e a r c h that u s e d auditory discrimination a s a s e c o n d a r y task. In a study involving the effects of divided attention on e n c o d i n g a n d retrieval, lidaka, A n d e r s o n , K a p u r , C a b e z a a n d C r a i k (2000) reported the p e r c e n t a g e of w o r d s recalled w h e n e n c o d i n g performed a l o n e w a s 7 9 % . T h e p e r c e n t a g e of correct words recalled dropped to 5 8 % w h e n e n c o d i n g w a s d o n e with a tone discrimination task (magnitude c h a n g e of 2 6 . 5 8 % ) . T h i s finding s u g g e s t e d that performing tone discrimination is attention d e m a n d i n g . Klingberg a n d R o l a n d (1997) reported a 1 5 . 6 6 % c h a n g e in r e s p o n s e time to detect a pitch c h a n g e in a s e r i e s of p r e s e n t e d tones w h e n c o m b i n e d with a visual detection task.  T h e greater s e c o n d a r y task costs obtained in this experiment c o m p a r e d to previous studies (lidaka, A n d e r s o n , K a p u r , C a b e z a & C r a i k , 2 0 0 0 ; Klingberg & R o l a n d , 1997) is likely d u e to the greater attentional d e m a n d s required by P D A t a s k s . T h e finding that tone discrimination performance w a s affected to a greater extent by navigation t a s k s than by d a t a entry t a s k s s u g g e s t that navigation is more attention d e m a n d i n g than data entry. R e s p o n s e times for adjusted identifications did not significantly differ for the D a t a Entry a n d Navigation conditions. T h e null difference s u g g e s t s that the difference in the percentage of adjusted identifications in the data entry a n d navigation conditions w a s not d u e to simply placing more attention while performing data entry t a s k s c o m p a r e d to navigation t a s k s . O n e of the c o m m o n criticisms of using a dual-task m e t h o d o l o g y to a s s e s s attention is that the results c a n be explained either by attention or task switching. In task switching, individuals w h o perform two concurrent t a s k s allocate their attention to only o n e task at a time. T o attend to the s e c o n d task, individuals n e e d to d i s e n g a g e from the current task a n d re-allocate their attention the s e c o n d task. In order to attend to the first task a g a i n , individuals n e e d to re-allocate their attention b a c k to the first task. A c c o r d i n g to task switching, it is p o s s i b l e that participants find it more difficult to switch between navigation a n d tone discrimination c o m p a r e d to data entry a n d tone discrimination. T h u s lower a c c u r a c y performance in the Navigation condition could a l s o be explained by task switching. T h e s e c o n d study w a s carried out to investigate whether the findings in Experiment 1 w e r e d u e to task switching or attention.  22  Experiment 2 E x p e r i m e n t 2 w a s d e s i g n e d to investigate w h e t h e r the dual-task methodology u s e d in E x p e r i m e n t 1 a s s e s s e d the attentional d e m a n d s of different kinds of P D A t a s k s , the difficulty of switching between the P D A t a s k s a n d tone discrimination task, or a combination of the two factors. T h e general d e s i g n of E x p e r i m e n t 2 w a s the s a m e a s for Experiment 1. A n additional factor of the tone discrimination task, e a s y a n d hard w a s included in this experiment. T h e additional factor permitted manipulation of the required attentional r e s o u r c e s to perform the tone discrimination task; more attention is required for the hard v e r s i o n c o m p a r e d to the e a s y v e r s i o n . I e x p e c t e d that, a s in Experiment 1, adjusted identifications in the tone discrimination task would be lower w h e n performed together with navigation tasks than data entry t a s k s . If navigation requires more attention than data entry, then the differences in the p e r c e n t a g e s of adjusted identifications b e t w e e n the hard a n d e a s y tone discrimination task would be greater a m o n g navigation t a s k s than a m o n g data entry t a s k s . C o n c u r r e n t l y performing a navigation task a n d hard tone discrimination task should be the most attention d e m a n d i n g , a n d the p e r c e n t a g e of adjusted identifications should be the lowest in this condition. S i n c e an e a s y tone discrimination task requires less attention, the p e r c e n t a g e of adjusted identifications s h o u l d a l s o be lower, but to a l e s s e r extent c o m p a r e d to a hard version of the tone discrimination task. In contrast, since data entry t a s k s require less attention, there is more leftover attention to perform the tone discrimination task. T h e percentage of adjusted identifications should be similar while performing either a n e a s y or hard tone discrimination task. O n the other h a n d , if the dual-task methodology w h i c h u s e s tone discrimination is sensitive to task switching, then switching between a navigation task a n d tone discrimination s h o u l d be equally difficult should be more difficult than switching between 23  a data entry task a n d tone discrimination. In addition, switching between a tone discrimination task ( e a s y or hard) a n d a P D A task (data entry or navigation) would be equally difficult. T h u s , I e x p e c t e d that, similar to E x p e r i m e n t 1, the overall the percentage of adjusted identifications would be lower w h e n the tone discrimination task w a s c o m b i n e d with navigation t a s k s c o m p a r e d to data entry t a s k s . In addition, I e x p e c t e d that the difference in the percentage of adjusted identifications would be similar b e t w e e n a n e a s y a n d hard tone discrimination task w h e n c o m b i n e d with navigation t a s k s . Lastly, I e x p e c t e d that he difference in the p e r c e n t a g e of adjusted identifications would be similar between an e a s y a n d hard tone discrimination task w h e n c o m b i n e d with d a t a entry t a s k s . Method Participants Thirty undergraduate students w e r e recruited through the subject pool at the P s y c h o l o g y department in the University of British C o l u m b i a . T h e y participated individually in this o n e s e s s i o n study lasting approximately 6 0 minutes. T h e y were c o m p e n s a t e d with o n e c o u r s e credit in return for their participation. T h e experiment w a s c o n d u c t e d with the approval of the University of British C o l u m b i a behavioral ethical review b o a r d . Apparatus T h e s a m e d e v i c e a s in Experiment 1 w a s u s e d . Tone Discrimination Task T h e materials, d e s i g n a n d instructions for the tone discrimination task w e r e the s a m e a s for E x p e r i m e n t 1, e x c e p t for the duration of the IS I. T h e interval from the onset of o n e tone to the onset of the next w a s narrowed to 6 0 0 m s , 1 1 0 0 m s , a n d 1 6 0 0 m s .  24  F r o m the results E x p e r i m e n t 1, the m e a n of m e d i a n r e s p o n s e time w a s no greater than 1200 m s . T h u s , the ISI w a s r e d u c e d s i n c e the extra time w a s not n e e d e d . P D A Tasks T w e l v e t a s k s c o m m o n l y performed on a P D A w e r e s e l e c t e d for this study. A greater n u m b e r of t a s k s w e r e included for this experiment s o that there were three P D A t a s k s in e a c h condition that involved a P D A task. T h i s n u m b e r of P D A t a s k s per condition w a s c h o s e n to obtain a n appropriate s a m p l e of P D A task performance. S i x t a s k s required participants to navigate through the m e n u s : Find a picture, retrieve appointments, c h e c k the battery, find a v o i c e recording, find a n email a d d r e s s , and find owner information. T h e other 6 t a s k s required participant to enter text on a Q W E R T Y keyboard using a stylus: Enter s e n t e n c e s , n a m e n e w folder, enter contact information, enter email m e s s a g e , enter appointment information, a n d enter e x p e n s e information. Six of the twelve t a s k s w e r e identical to the o n e s u s e d in E x p e r i m e n t 1. T h e newly a d d e d t a s k s in E x p e r i m e n t 2 will be d e s c r i b e d below. E a c h of t h e s e t a s k s c a n be completed in a n u m b e r of different w a y s . T a b l e 3 s h o w s the n u m b e r of number of steps required for completing e a c h task in the most efficient or optimal manner. Table 3 Find a voice recording. F o r this task, participants w e r e required to locate the folder n a m e d ' P e r s o n a l ' a n d to play the voice m e s s a g e n a m e d 'recording'. Find an email address. Participants w e r e instructed to find, a n d display on the s c r e e n , the email a d d r e s s for the contact ' A p h a s i a project'. Find the owner. F o r this task, participants w e r e required to s e a r c h through several m e n u s to find the s c r e e n that s h o w e d the n a m e of the d e v i c e owner. Enter sentences. Participants w e r e instructed to enter two s e n t e n c e s into a Word document. 25  Enter an email message. T h i s task required participants to enter a brief m e s s a g e into the email c o m p o s e r in the d e v i c e . Name a new folder. Participants were required to create a n e w folder and n a m e it 'Experiment results'. Design T h e d e s i g n of this experiment w a s a 2 x 2 factorial with tone discrimination difficulty (easy, hard) a n d task condition (baseline, d a t a entry, navigation) manipulated as within subjects factors. T h e baseline condition w a s included in order to find two difficulty levels w h e r e a c c u r a c y w a s approximately 8 0 % for the e a s y tone discrimination condition a n d approximately 7 0 % for the hard tone discrimination condition for e a c h participant. T h e s e a c c u r a c y levels w e r e s e l e c t e d b e c a u s e they reflect performance that is off the ceiling, while leaving sufficient d o w n - s i d e room for revealing the additional resource d e m a n d s of the concurrent P D A tasks w h i c h had to be c o m p l e t e d in the data entry a n d navigation condition. Procedures I tested participants individually in a s e s s i o n that lasted approximately 60 minutes. U p o n obtaining their written consent, I administered the t a s k s in the order d e s c r i b e d below. E a c h participant first completed the tone discrimination task a l o n e in the baseline condition in order to find a f r e q u e n c y difference between the standard a n d target tone at which a level of a c c u r a c y w a s approximately 8 0 % a n d 7 0 % . T h e s e performance levels were identified by m e a n s of the s a m e calibration p r o c e d u r e a s in E x p e r i m e n t 1. In the next p h a s e of the experiment, participants c o m p l e t e d either an e a s y or hard tone discrimination task together with the P D A t a s k s listed in T a b l e 3. E a c h participant c o m p l e t e d the s a m e set of P D A t a s k s in combination with a tone 26  discrimination task. P r e s e n t a t i o n of the four conditions ( P D A task type by tone discrimination task difficulty) w a s c o u n t e r b a l a n c e d by m e a n s of a Latin S q u a r e d e s i g n . T h e instructions for performing a P D A task concurrently with a tone discrimination task w e r e the s a m e a s in Experiment 1. T h e p r o c e d u r e s for starting a n d ending the tone discrimination task, a s well a s p r o c e d u r e s for recording P D A task performance, w e r e the s a m e a s in Experiment 1. After the last P D A task w a s c o m p l e t e d , participants w e r e given a verbal debriefing, a s well a s a debriefing form, a n d c o u r s e credit. Results Data Preparation T h e c o d i n g m a n u a l for the P D A t a s k s w a s d e v e l o p e d in the s a m e w a y a s in Experiment 1. T h e m e t h o d s for coding P D A task p e r f o r m a n c e a n d calculating tone discrimination task p e r f o r m a n c e w e r e s a m e a s in E x p e r i m e n t 1. All data w e r e c h e c k e d a n d corrected for transcription a n d c o d i n g errors until a c c u r a c y w a s greater than 9 9 % . T h e results from the tone discrimination task a n d P D A tasks w e r e s c r e e n e d for outliers, defined a s falling more than three standard deviations a w a y from the s a m p l e m e a n . T h e r e w e r e two outliers d i s c o v e r e d in the tone discrimination task a n d 1 outlier in the P D A t a s k s . E a c h outlier w a s replaced with a number either 3 standard deviations a b o v e or below the s a m p l e m e a n , respectively. S i x participants did not m a k e any correct identification o n the tone discrimination task while concurrently completing a P D A task. Data from t h e s e participants were e x c l u d e d from the a n a l y s e s . T h e data from the remaining 2 4 participants were included for the a n a l y s e s . T h e r e w e r e five missing v a l u e s in the P D A t a s k s . E a c h value w a s replaced with the a v e r a g e v a l u e from that variable.  27  P D A Tasks T h e d e p e n d e n t m e a s u r e s for the P D A t a s k s w e r e the p e r c e n t a g e of correct p r e s s e s , the p e r c e n t a g e of errors in the data entry a n d navigation t a s k s , s p e e d of data entry, and the a m o u n t of time to complete navigation t a s k s . O v e r a l l , two-thirds of the p r e s s e s (M = 66.23) in the navigation tasks were correct. A n in depth examination of the navigation errors by e a c h task reveals that the percentage of errors ranged from 8 . 1 5 % to 4 9 . 1 5 % . Nearly half of the total p r e s s e s while finding the battery w e r e errors (M = 4 9 . 1 5 , SD = 23.51). Other t a s k s had slightly fewer errors, s u c h a s finding the page for renaming the folder (M = 4 2 . 6 7 , SD - 19.36), followed by finding a v o i c e recording (M = 4 3 . 3 8 , SD = 20.00), finding appointments (M = 32.52, SD = 21.85), creating a new d o c u m e n t in W o r d (M = 2 8 . 0 0 , S D = 31.27), creating a n e w e m a i l m e s s a g e (M = 32.94, S D = 29.79), finding the appropriate date for entering information (M = 3 1 . 4 6 , S D = 19.80), creating a n e w contact (M = 2 3 . 4 6 , S D = 28.70), finding a n email m e s s a g e (M = 23.29, S D = 27.58), a n d finding the page that displays the o w n e r of the d e v i c e (M = 2 2 . 4 6 , S D = 23.17). T h e fewest errors were m a d e for finding the E x c e l s h e e t to enter information {M = 8.15, S D = 15.22). T h e percentage of errors for finding the E x c e l sheet w a s substantially lower than the rest of the navigation t a s k s , a n d w a s probably not representative of navigation. This task w a s not included in further a n a l y s e s . A l m o s t all the p r e s s e s m a d e during data entry w e r e correct. Of the total p r e s s e s , 6 . 5 % were errors. T h e p e r c e n t a g e of data entry errors a c r o s s t a s k s ranged from 2 . 6 7 % to 8 . 8 3 % . T h e greatest p e r c e n t a g e of errors were m a d e w h e n re-naming a folder (M = 8.83, S D = 9.76), followed by entering appointment information (M = 7.84, S D = 6.19), entering contact information (M - 7.52, S D = 4.22), typing a n email m e s s a g e (M = 7.37,  28  SD = 6.68), a n d entering s e n t e n c e s into W o r d (M = 5.07, SD = 4.11). T h e least percentage of errors w a s m a d e w h e n entering data in the E x c e l sheet. T h e p e r c e n t a g e of errors of e a c h P D A task type a c r o s s tone discrimination difficulty, a s well a s the s t a n d a r d errors, is d i s p l a y e d in Figure 3. Participants m a d e a slightly greater p e r c e n t a g e of navigation errors in the e a s y tone discrimination condition c o m p a r e d to hard tone discrimination condition. S i m i l a r to navigation t a s k s , participants m a d e a slightly greater p e r c e n t a g e of data entry errors in the e a s y tone discrimination c o m p a r e d to the hard tone discrimination condition. Figure 3 A two-way A N O V A w a s c o n d u c t e d on the error data with the P D A task types (data entry, navigation) a n d tone discrimination difficulty ( e a s y , hard) a s within-subjects factors. T h e a n a l y s i s confirmed the observation that participants m a d e more errors while performing navigation t a s k s than data entry t a s k s , F (1, 23) = 1 8 8 . 7 1 , MSE 78.54, p < . 0 0 1 , f  -  = 2 . 1 9 . N o other effects w e r e significant.  T y p i n g rate w a s slightly s l o w e r in the hard tone discrimination condition (M = 12.57, SD = 2.26) c o m p a r e d to the e a s y tone discrimination condition (M = 14.59, SD = 2.91). T y p i n g rate w a s the quickest for renaming a folder (M = 17.50, SD = 4.39), followed by entering s e n t e n c e s in W o r d {M = 15.59, SD = 3.86), typing an email m e s s a g e {M = 15.12, SD = 4.77), entering appointment information (M = 13.65, S D = 3.63), entering contact information (M=  10.68, S D = 2.02), a n d entering information in  a n E x c e l s h e e t (M = 9.48, S D = 1.85). T h e results using a paired s a m p l e s f-test  Cohen's f (1988) is the appropriate effect size measurement used in the context of an F-test. Cohen's f and eta-squared (a power parameter commonly reported with the F-test statistics) are related in the following manner: f - e t a / (1-eta ). 1  2  2  29  revealed that participants entered data at a significantly q u i c k e r rate while performing a n e a s y c o m p a r e d to hard tone discrimination task, t (23) = 4 . 9 1 , p < . 0 0 1 , d = 0.78. 2  A v e r a g e completion time for navigation t a s k s while completing a n e a s y tone discrimination task w a s slightly greater {M = 3 1 . 8 5 , SD = 9.30) c o m p a r e d to while completing a hard tone discrimination task (M = 2 4 . 4 5 , S D = 7.21). T h e completion times ranged from a n a v e r a g e of 55.46 s ( S D = 31.48) to 11.86 s ( S D = 12.18). Participants took the longest while finding the appropriate s c r e e n to r e n a m e a folder, followed by finding a v o i c e recording (M = 52.67, S D = 29.11), finding the battery (M = 4 0 . 8 3 , S D = 20.86), finding the appointment dates (M = 3 6 . 2 9 , S D = 27.08), finding the appropriate date for entering appointment information (M = 3 1 . 2 5 , S D = 20.02), finding a picture (M = 3 0 . 7 1 , S D = 28.57), c o m p o s i n g a new email m e s s a g e (M = 2 8 . 1 3 , S D = 24.16), finding the s c r e e n that d i s p l a y s the o w n e r of the d e v i c e (M = 17.58, S D = 14.62), creating a n e w W o r d d o c u m e n t (M = 15.59, S D = 16.02), creating a new contact (M = 15.59, S D = 16.09), a n d finding an email m e s s a g e . T h e results using a paired s a m p l e s f-test confirmed that participants found the required information significantly faster while performing a hard c o m p a r e d to an e a s y tone discrimination task, f (23) = 3.24, p < .01, d=  1.40.  Tone Discrimination Task T h e d e p e n d e n t m e a s u r e s for the tone discrimination task, in e a c h condition, were the p e r c e n t a g e of correct, incorrect, and adjusted identifications of target tones, and the time required to m a k e correct identifications. s h o w s the m e a n p e r c e n t a g e of correct, incorrect, a n d adjusted identifications of target tones for e a c h condition. A s e x p e c t e d , participants w e r e l e s s accurate while performing a hard c o m p a r e d to e a s y tone discrimination task in the B b s e l i n e condition.  2  Cohen's d (1988) is the appropriate effect size measure to use in the context of a Mest on means.  30  A m o n g the data entry conditions, participants m a d e a greater p e r c e n t a g e of correct identifications while completing a n e a s y c o m p a r e d to hard tone discrimination task. Similarly, in the navigation conditions participants m a d e a greater percentage of correct identifications while completing a n e a s y c o m p a r e d to a hard tone discrimination task.  Overall, the p e r c e n t a g e of incorrect identifications w a s the greatest in the B a s e l i n e conditions (M = 2.43), followed by the navigation (M = 1.82), a n d data entry conditions {M = 1.35). In the b a s e l i n e condition, participants m a d e approximately twice the percentage of incorrect identifications for the e a s y tone discrimination task c o m p a r e d to the hard tone discrimination task [see ]. In the navigation conditions, participants m a d e approximately the s a m e p e r c e n t a g e of incorrect identifications for a n e a s y a n d for a hard tone discrimination task. W h i l e participants w e r e completing data entry t a s k s , they m a d e a slightly greater percentage of incorrect identifications while performing a hard v e r s u s a n e a s y T o n e Discrimination T a s k . In order to take into a c c o u n t the different p e r c e n t a g e of incorrect identifications a c r o s s conditions, the adjusted identifications w e r e explored in detail Q. T h e pattern of results for adjusted identifications w a s the s a m e a s for the pattern of correct identifications. A greater p e r c e n t a g e of adjusted identifications w a s found w h e n participants c o m p l e t e d a n e a s y version of the T o n e Discrimination T a s k than the hard version. W h e n performed concurrently with data entry t a s k s , participants m a d e a similar percentage of adjusted identifications in the e a s y a n d hard v e r s i o n of the tone discrimination task. T h e p e r c e n t a g e of adjusted identifications w a s lower while participants performed a hard T o n e Discrimination T a s k c o m p a r e d to an e a s i e r version. A two-way A N O V A c o n d u c t e d on the adjusted identifications data with the task condition (baseline, data entry, navigation) a n d tone discrimination difficulty (easy, hard) 31  as the within-subjects factors confirmed the o b s e r v a t i o n s . Participants m a d e a significantly greater p e r c e n t a g e of adjusted identifications while performing an e a s y tone discrimination task, F (1, 23) = 3 3 . 4 9 , MSE = 3 9 4 . 7 0 , p < . 0 0 1 , / = 1.16. A main effect of Ttsk condition w a s a l s o f o u n d , F (2, 46) = 5 6 . 9 9 , MSE = 3 0 9 . 8 7 , p < . 0 0 1 , / = 2.16. A post-hoc test c o n d u c t e d with F i s h e r ' s L S D revealed that the percentage of adjusted identifications in the b a s e l i n e condition w a s significantly greater than the data entry condition, a n d that the percentage of correct identifications in the navigation condition w a s significantly l e s s c o m p a r e d to the data entry condition. T h e critical a n a l y s e s w e r e to e x a m i n e whether the p e r c e n t a g e of adjusted identifications varied b e t w e e n P D A task types a c r o s s tone discrimination difficulty. T h e m e a n difference of adjusted identifications a m o n g navigation conditions (M = 17.14, SD = 22.7'4) w a s greater than a m o n g data entry conditions (M = 9 . 5 1 , SD = 21.65). A paired s a m p l e s f-test c o n d u c t e d on the m e a n differences between the two conditions revealed that the difference a p p r o a c h e d significance, f (23) = 1.75, p = .09. S i n c e the pattern of results did not c h a n g e e v e n w h e n taking into account the incorrect identifications d a t a , only the r e s p o n s e times for correct identifications were explored. T h e s u m m a r i z e d results for r e s p o n s e times ( m e a n of m e d i a n s ) of correct identifications are d i s p l a y e d in Figure 4. O v e r a l l , participants took longer to respond to target tones while performing data entry tasks (M = 861.04) a n d navigation tasks (M = 947.00) c o m p a r e d to the B a s e l i n e condition (M = 787.85). T i m e required for responding to target tones while completing data entry t a s k s w a s approximately the s a m e w h e n participants w e r e concurrently performing an e a s y or a hard T o n e Discrimination T a s k . However, r e s p o n s e time while performing navigation t a s k s w a s greater while attending to a hard c o m p a r e d to e a s y T o n e Discrimination T a s k .  32  Figure 4 A 2 x 3 A N O V A w a s c o n d u c t e d on the r e s p o n s e time data with the task condition (baseline, data entry, navigation) a n d tone discrimination difficulty (easy, hard) a s the within-subjects factors. T h e a n a l y s i s confirmed that participants took significantly longer to correctly identify target t o n e s w h e n performing a hard c o m p a r e d to a n e a s y tone discrimination task, F (1, 23) = 6.66, MSE = 2 9 0 7 3 . 5 6 , p < . 0 0 1 , / = 0.49. A significant main effect of task condition w a s found F (2, 46) = 19.21, MSE = 1 5 8 5 2 . 6 2 , p < . 0 0 1 , / = 1.23. T h e interaction effect w a s not significant. P o s t - h o c tests using F i s h e r ' s LSD revealed that r e s p o n s e time w a s significantly greater while participants were concurrently completing a P D A task. In addition, r e s p o n s e time w a s greater while performing navigation t a s k s c o m p a r e d to data entry t a s k s . T h e interaction w a s not significant. Discussion T h e primary objective of Experiment 2 w a s to explore w h e t h e r the findings obtained in E x p e r i m e n t 1 reflected measuring attention or task switching. T h e s e c o n d objective w a s to investigate whether the d e v e l o p e d dual-task methodology could be reliably u s e d . W e required participants to perform an e a s y or hard version of the tone discrimination task while completing a set of P D A t a s k s that either f o c u s e d on navigation or data entry. Overall, the navigation task error rate w a s greater than the data entry error rate. T h e error rates for both P D A t a s k s w e r e slightly better w h e n c o m b i n e d with a hard version of a T o n e Discrimination T a s k c o m p a r e d to a n e a s y v e r s i o n , but the difference w a s not significant. Performing hard tone discrimination s l o w e d d o w n information s e a r c h ; performing e a s y tone discrimination s l o w e d d o w n data entry s p e e d .  33  T h e completion time a n d data entry s p e e d should be interpreted with caution. T h e time data reported a l s o reflects the e x c h a n g e of instructions between the participants a n d experimenter, a n d w h e n participants a s k e d for help. O n e possible interpretation of the finding is that participants a s k e d for m o r e help in o n e condition, thus slowing d o w n data entry. A n o t h e r possible interpretation for the findings is that participants w a s more relaxed w h e n they realized that entering d a t a a n d attending to e a s y tone discrimination w a s not difficult, a n d therefore took more time to enter the data. In g e n e r a l , P D A task performance w a s c o m p a r a b l e to findings in studies that had participants c o m p l e t e t h e s e t a s k s with full attention (Graf & L i , 2007), indicating that participants w e r e paying attention to performing t h e s e t a s k s . T h e p e r c e n t a g e of adjusted identifications w a s significantly lower a n d the m e d i a n r e s p o n s e time w a s significantly slower while performing the hard tone discrimination task c o m p a r e d to the e a s y v e r s i o n in the baseline condition. T h e findings suggest that the difficulty manipulation w a s s u c c e s s f u l , and that the hard v e r s i o n of the task required more attention than the e a s y v e r s i o n . A s e x p e c t e d , the difference in adjusted identifications w a s greater between navigation conditions c o m p a r e d to the data entry conditions. R e s p o n s e time w a s the greatest w h e n participants w e r e completing navigation t a s k s with a hard tone discrimination task. W e w e r e able to replicate the majority of findings from E x p e r i m e n t 1. C o n s i s t e n t with E x p e r i m e n t 1, participants m a d e more errors in navigation t a s k s c o m p a r e d to data entry t a s k s . O v e r a l l , the p e r c e n t a g e of navigation errors w a s slightly lower and overall time to c o m p l e t e navigation t a s k s w a s slightly quicker c o m p a r e d to Experiment 1. T h e overall data entry error rate w a s similar to Experiment 1. H o w e v e r , data entry s p e e d w a s slightly s l o w e r than what w a s found in Experiment 1. 34  O v e r a l l , the pattern of adjusted identifications w a s similar to what w a s found in Experiment 1. T h e p e r c e n t a g e of adjusted identifications w a s lower w h e n performing a P D A task a n d a tone discrimination task c o m p a r e d to performing only the tone discrimination task a l o n e . T h e effect size of adjusted identifications for data entry a n d navigation conditions w e r e c o m p a r a b l e to the results from E x p e r i m e n t 1. R e s p o n s e time for correct identifications while completing data entry t a s k s w a s q u i c k e r than what w a s found in E x p e r i m e n t 1. T h e reduced r e s p o n s e time c o m p a r e d to E x p e r i m e n t 1 is most likely d u e to the r e d u c e d inter-stimulus interval. T h e r e is e v i d e n c e that r e s p o n s e time varies a s a function of inter-stimulus interval ( F r a n c e et a l . , 2002). Auditory trace d e c a y s a s a function of time. In longer ISI's, participants take longer to retrieve the c o m p a r i s o n tone prior to m a k i n g a d e c i s i o n . In s u m m a r y , the findings from Experiment 2 provide support that a dual-task methodology using tone discrimination is a valid set-up for a s s e s s i n g the attentional d e m a n d s of P D A t a s k s . In addition, the replicated findings from Experiment 2 also suggest that this method c a n be u s e d reliably in the context of m e a s u r i n g attention required by P D A t a s k s . Finally, E x p e r i m e n t s 1 a n d 2 provide c o n v e r g i n g e v i d e n c e that navigation t a s k s require more attention to perform than text entry t a s k s . W h i l e there h a v e b e e n m a n y r e s e a r c h e r s that study attention a s a single resource, a s e c o n d a c c o u n t of attention a r g u e s that attention c o n s i s t s of distinct reserves w h e r e e a c h r e s o u r c e is responsible for p r o c e s s i n g different types of information ( B a d d e l e y , 1986). T h e following two e x p e r i m e n t s w e r e d e s i g n e d to explore whether different types of attention are required to perform navigation a n d data entry tasks.  35  Experiment 3 T h e p u r p o s e of this study w a s to validate a m e t h o d o l o g y for exploring the different types of attentional r e s o u r c e s required for navigation a n d data entry t a s k s . I c h o s e a n existing m e t h o d , d e s c r i b e d by B r o o k s (1968), for revealing different types of attention: V i s u o - s p a t i a l a n d articulatory/auditory. T h i s method required participants to perform two t a s k s concurrently. Participants c o m p l e t e d a combination of o n e input task (letter tracing task, s e n t e n c e d e c i s i o n task) and o n e output task (pointing, tapping, saying). O n e input task required visuo-spatial r e s o u r c e s (letter tracing task), while the other task required articulatory/auditory r e s o u r c e s ( s e n t e n c e d e c i s i o n task). T h e letter tracing task involved presenting a n image of an E n g l i s h block letter (e.g., s e e Figure 5) and making categorization j u d g e m e n t s . F o r this task, participants w e r e a s k e d to d e c i d e whether e a c h corner w a s the topmost/bottom-most corner in the letter, or whether e a c h corner w a s o n the outside e d g e of the letter. T h e s e n t e n c e d e c i s i o n task required participants to c a t e g o r i z e e a c h word in a s e n t e n c e presented o v e r the s p e a k e r s . T h e y w e r e required to d e c i d e w h e t h e r e a c h word w a s a n o u n / n o n - n o u n or article/non-article. F o r both t a s k s , participants w e r e required to provide ' y e s ' or 'no' a n s w e r s .  Figure 5 T h e three output t a s k s required participants to indicate their a n s w e r s from the Input T a s k s in o n e of three w a y s . Participants m a d e their r e s p o n s e s by a method that required either visuo-spatial r e s o u r c e s (pointing), articulatory/auditory r e s o u r c e s (saying), or motor abilities (tapping). A combination of t h e s e t a s k s (i.e., o n e input task a n d o n e output task) would be then u s e d in conjunction with the P D A t a s k s to explore the type of attention required by the P D A t a s k s .  36  I e x p e c t to find the s a m e pattern of results reported in the original study (Brooks, 1968). C o m p l e t i o n times would be greater w h e n both t a s k s d r a w on the s a m e type of r e s o u r c e s c o m p a r e d to w h e n the two t a s k s require different attentional r e s o u r c e s . Specifically, completion time would be greater for the letter tracing task w h e n responding in a m a n n e r that requires visuo-spatial attention c o m p a r e d to responding by a method that requires articulatory/auditory attention (i.e., s a y i n g the r e s p o n s e s ) . In addition, I predicted that completion time would be greater for the s e n t e n c e d e c i s i o n task w h e n verbally indicating the r e s p o n s e s c o m p a r e d to indicating a n s w e r s by a method that requires visuo-spatial p r o c e s s i n g . Methods Participants T w e n t y - s e v e n undergraduate students were recruited through the subject pool in the p s y c h o l o g y department at the University of British C o l u m b i a . T h e y w e r e c o m p e n s a t e d with o n e c o u r s e credit in return for their participation. T h e experiment w a s c o n d u c t e d with the approval of the University of British C o l u m b i a behavioral ethics review b o a r d . Materials T h e stimuli for the letter tracing task c o n s i s t e d of an outline of six block letters. T w o letters w e r e for practice trials and the remaining four letters w e r e for the test trials. E a c h letter for the practice trials [shown in Figure 5] had 12 c o r n e r s : E , H. E a c h letter for the test trials [shown in Figure 6] had ten corners: F, N, G , a n d Z . E a c h letter w a s drawn using M S Paint a n d stored a s a bitmap file. Figure 6 T h e stimuli for the s e n t e n c e d e c i s i o n task c o n s i s t e d of six f a m o u s English a p h o r i s m s (e.g., a bird in the hand is not in the bush). T w o s e n t e n c e s w e r e u s e d for the 37  practice trials, a n d the remaining four s e n t e n c e s w e r e u s e d for the test trials. E a c h s e n t e n c e in the practice trial had a length of twelve w o r d s : Y o u ' l l never plow a field by turning it o v e r in your m i n d ; the g r a s s is always g r e e n e r on the other side of the f e n c e . E a c h s e n t e n c e in the test trial had a length o f t e n w o r d s : R i v e r s from the hills bring fresh water to the cities; a bird in the hand is not in the b u s h ; there is the low fiend who stole the child's c a n d y ; no m a n w h o h a s a wife is still a bachelor. E a c h s e n t e n c e w a s recorded by s p e a k i n g through a m i c r o p h o n e , a n d stored a s a .wav file, with single c h a n n e l 16-bit P C M c o d i n g at a s a m p l i n g rate of 44.1 k H z . Input Tasks Letter Tracing Task. Stimulus presentation a n d r e s p o n s e recording for the letter tracing task w e r e controlled by a P C , using the E P r i m e v.1.0 software ( P s y c h o l o g y Software T o o l s Inc., Pittsburg, P A ) . T h e stimuli, d e s c r i b e d in the Materials section, w e r e presented o n a 15" monitor. T h e letter tracing task required participants to c a t e g o r i z e e a c h corner of a block letter. T h e letter tracing task c o n s i s t e d of two practice trials a n d four test trials (one trial for e a c h letter). In e a c h trial of this task, a letter w a s p r e s e n t e d on the monitor on a white b a c k g r o u n d . Participants were allowed to view the letter a s long a s they n e e d e d . After participants indicated that they could r e m e m b e r the s h a p e of the letter, the stimulus w a s taken off the monitor. Participants w e r e instructed to imagine the letter to e n s u r e that they could g e n e r a t e a mental image of the letter. Participants w e r e s h o w n the letter again if they indicated that they could not r e m e m b e r . W h e n participants indicated that they could r e m e m b e r the s h a p e of the letter, the i m a g e w a s taken off the monitor. Next, o n e of the categorization instructions w a s p r e s e n t e d on the s c r e e n . Participants w e r e required to begin the task starting at the bottom left corner of the letter a n d to c a t e g o r i z e the c o r n e r s in a c l o c k w i s e direction until all c o r n e r s w e r e c a t e g o r i z e d . 38  In the top/bottom instruction, participants w e r e a s k e d to c a t e g o r i z e the corners that were the highest point or the lowest point in the letter a s ' y e s ' a n d all other corners a s 'no' (see Figure 7). F o r e x a m p l e , the correct s e q u e n c e of r e s p o n s e s for the ' F ' stimulus would be " y e s , y e s , y e s , no, no, no, no, no, no, y e s " . T h e outside instruction required participant to c a t e g o r i z e e a c h corner that t o u c h e d a n imaginary box surrounding the letter a s ' y e s ' a n d all other corners a s 'no' (see Figure 8). T h e correct s e q u e n c e of r e s p o n s e s for the ' F " stimulus would be "yes, y e s , y e s , y e s , no, no, no, no, no, yes". Figure 7  Figure 8 Sentence Decision Task. Stimulus presentation a n d r e s p o n s e recording for the s e n t e n c e d e c i s i o n task w e r e controlled by a P C , using the E P r i m e v. 1.0 software ( P s y c h o l o g y Software T o o l s Inc., Pittsburg, P A ) . T h e s e n t e n c e s w e r e presented over two s p e a k e r s . T h e s e n t e n c e d e c i s i o n task consisted of two practice trials a n d four trials (one trial for e a c h s e n t e n c e ) . T h e s e n t e n c e d e c i s i o n task required participants to categorize e a c h word immediately after a presented s e n t e n c e . In e a c h trial of this task, a s e n t e n c e w a s presented auditorily through two s p e a k e r s . After the s e n t e n c e w a s p r e s e n t e d , participants w e r e a s k e d to repeat the s e n t e n c e to e n s u r e that they w e r e able to recite the s e n t e n c e perfectly. T h e s e n t e n c e w a s repeated if participants recited the s e n t e n c e incorrectly. After correcting the participants, they w e r e a s k e d to repeat the complete s e n t e n c e a g a i n . W h e n participants were able to r e h e a r s e the s e n t e n c e perfectly, o n e of the two categorization instructions w a s p r e s e n t e d . In the noun instruction, participants were required to c a t e g o r i z e e a c h word (in serial order) that w a s a noun a s 'yes' and all  39  other w o r d s a s 'no'. In the article instruction, participants w e r e required to categorize e a c h word that w a s a n article a s 'yes' and all other w o r d s a s 'no'. Output Tasks Pointing. A list of Y a n d N w a s d i s p l a y e d in a s t a g g e r e d m a n n e r on a computer monitor [see Figure 9]. T h e Y ' s and N's w e r e s t a g g e r e d to force c l o s e visual monitoring of pointing. E a c h line d i s p l a y e d o n e Y and o n e N. A total of 12 lines of Y ' s and N's w e r e presented on the s c r e e n for a practice trial, s i n c e there w e r e 12 corners on e a c h stimulus of the practice trial. T e n lines were presented for a test trial, s i n c e there were ten corners on e a c h stimulus of the test trial. Participants clicked o n either a Y or N on e a c h line to m a k e o n e r e s p o n s e , starting from the top line. Participants u s e d a m o u s e to point a n d click at the Y (for y e s ) a n d N (for no). Figure 9 Tapping. In the tapping output condition, participants p r e s s e d a button on a keyboard that c o r r e s p o n d e d to a 'yes' with their left index finger a n d another button for a 'no' r e s p o n s e with their right index finger. Saying. In the s a y i n g output condition, participants r e s p o n d e d by saying 'yes' and 'no' into a m i c r o p h o n e . Neuropsychological  Tests  A n e u r o p s y c h o l o g i c a l test battery w a s e m p l o y e d to a s s e s s participants' cognitive abilities. T h e battery c o n s i s t e d of four standardized tests: the F o r w a r d C o r s i B l o c k tapping task ( C o r s i , 1 9 7 2 ; K e s s e l s , Zandvoort, P o s t m a , K a p p e l l e a n d H a a n , 2000), the R e v e r s e C o r s i B l o c k tapping task (Corsi, 1972; K e s s e l s , Z a n d v o o r t , P o s t m a , K a p p e l l e & H a a n , 2000), the F o r w a r d s Digit s p a n test ( W e c h s l e r , 1981), a n d the R e v e r s e Digit S p a n T e s t ( W e c h s l e r , 1981). T h e tests were administered a c c o r d i n g to the standardized  40  instructions published in e a c h m a n u a l . T h e results of t h e s e m e a s u r e s are not pertinent to the objectives of the present thesis and thus will not be included. Design T h e d e s i g n of this experiment c o n s i s t e d of a 2 x 3 factorial d e s i g n that had input task (letter tracing task, s e n t e n c e d e c i s i o n task) a n d output task (pointing, tapping, saying) a s within subject factors. Procedures I tested participants individually in a s e s s i o n that lasted 6 0 minutes. U p o n obtaining their written c o n s e n t , e a c h participant c o m p l e t e d the t a s k s d e s c r i b e d below. T h e r e w e r e a total of six conditions in this experiment. In e a c h condition, participants c o m p l e t e d either a letter tracing task or s e n t e n c e d e c i s i o n task, c o m b i n e d with o n e method of r e s p o n d i n g : pointing, tapping, s a y i n g . P r e s e n t a t i o n of the six conditions w a s c o u n t e r b a l a n c e d a c r o s s participants by m e a n s of a Latin S q u a r e d e s i g n . In e a c h condition, participants w e r e given two practice trials to familiarize them with the task, the categorization instructions, a n d the method of r e s p o n s e . Prior to beginning the practice trials, I explained to participants the g o a l of the task. F o r conditions that involved the s e n t e n c e decision task, I e x p l a i n e d to participants that they were to listen to a s e r i e s of short s e n t e n c e and m a k e categorization judgments for e a c h word. I then e x p l a i n e d e a c h categorization instruction (i.e., n o u n , article). O n c e participants indicated that they understood the task, I p r o c e e d e d to d e s c r i b e the method of r e s p o n s e for that condition. After the practice trials w e r e c o m p l e t e d , a block of four s e n t e n c e s w a s run a s the test trials. T h e stimuli a n d categorization instructions were randomly p r e s e n t e d a c r o s s trials. F o r the letter tracing task, I explained to participants that they w e r e required to look at a block letter presented on the monitor a n d to c a t e g o r i z e e a c h corner, in a 41  clockwise direction, starting from the bottom left corner. F o r e a c h letter, I told participants they w o u l d be a s k e d to m a k e categorization j u d g m e n t s for e a c h corner. Next, I explained e a c h categorization instruction. O n c e participants indicated that they understood the task, I p r o c e e d e d to d e s c r i b e the method of r e s p o n s e for that condition. T h e s e instructions w e r e the s a m e a s for the s e n t e n c e d e c i s i o n task. After the practice trials w e r e c o m p l e t e d , a block of four letters w e r e run a s the test trials. I instructed participants to m a k e their r e s p o n s e s immediately w h e n they m a d e a categorization. T h i s instruction w a s given to prevent participants from first collecting several a n s w e r s a n d then indicating the r e s p o n s e s , w h i c h w o u l d not reflect completion time p r o d u c e d by the interference. In addition, I told participants to be a s accurate a s possible in m a k i n g their r e s p o n s e s . T h e timing for e a c h trial b e g a n after the categorization instruction w a s presented and e n d e d w h e n participants m a d e the last response. Following the completion of the last condition, I administered the battery of n e u r o p s y c h o l o g i c a l tests. After the last n e u r o p s y c h o l o g i c a l test w a s c o m p l e t e d , participants w e r e given a verbal debriefing, a s well a s a written debriefing form, and a c o u r s e credit. Results Data Preparation T h e results from the t a s k s were s c r e e n e d for outliers, defined a s falling more than three standard deviations a w a y from the s a m p l e m e a n . O n e outlier that w a s three standard deviations a b o v e the m e a n w a s found. T h i s outlier w a s r e p l a c e d with a n o n outlying number, a n u m b e r that w a s 3 standard deviations a b o v e the s a m p l e m e a n .  42  O n e participant did not complete the four test trials of the s e n t e n c e d e c i s i o n task while m a k i n g verbal r e s p o n s e s . T h e data from this participant w e r e e x c l u d e d from the analysis. Data from the remaining 26 participants w e r e u s e d for the a n a l y s e s . T h e d e p e n d e n t m e a s u r e for the letter tracing task a n d s e n t e n c e d e c i s i o n task w a s the time it took to c o m p l e t e o n e trial. F o r e a c h participant, I c o m p u t e d the m e a n completion time for e a c h condition. Input and Output T a s k s M e a n completion time is s h o w n in Figure 10. O v e r a l l , completion time for the letter tracing task w a s 17.73 s ( S D = .85) a n d 16.04 s ( S D = .74) for the s e n t e n c e decision task, s u g g e s t i n g that the t a s k s w e r e of approximately the s a m e difficulty. T h e figure revealed that the two conditions that required o v e r l a p p i n g r e s o u r c e s had greater completion times c o m p a r e d to other conditions that had an input a n d output tasks that required different t y p e s of r e s o u r c e s . W h e n participants r e s p o n d e d by pointing to a n s w e r s , completion time for the letter tracing task (M = 2 6 . 8 7 , S D = 7.34) w a s approximately twice a s long c o m p a r e d to categorizing w o r d s in a s e n t e n c e (M = 15.27, S D = 4.45). Similarly, completion time w a s greater w h e n participants m a d e v o c a l r e s p o n s e s for the s e n t e n c e d e c i s i o n task (M = 2 1 . 8 3 , S D = 6.01) c o m p a r e d to w h e n the performing the letter tracing task (M = 13.66, S D = 3.57). C o m p l e t i o n time in the tapping output condition w a s approximately the s a m e w h e n performing the letter tracing task (M = 12.85, S D = 3.57) a s in the s e n t e n c e d e c i s i o n task (M = 11.64, S D = 3.54). Figure 10 A two-way A N O V A w a s c o n d u c t e d on the completion time[s] with the input task (letter tracing task, s e n t e n c e d e c i s i o n task) and output task (pointing, tapping, saying) as the within-subjects factors. A main effect of output task w a s f o u n d , F (2, 50) = 79.24, MSE = 1 3 . 0 5 , p < . 0 0 1 , / = 0.86. T h e interaction between input a n d output task w a s 43  also significant, F (2, 50) = 115.38, MSE = 11.03, p < . 0 0 1 , / = 2.97. C o m p l e t i o n times between the input t a s k s w e r e not significantly different, p > .05. T w o follow-up paired s a m p l e s f-tests w e r e c o n d u c t e d on the completion times to explore whether completion time varied a c r o s s input a n d output t a s k s . C o m p a r i s o n between completion times confirmed the observations. W h e n participants pointed to the a n s w e r s , they took significantly longer to categorize c o r n e r s of a letter than to categorize w o r d s in a s e n t e n c e , t (26) = 9.04, p < . 0 0 1 . W h e n participants indicated their a n s w e r s verbally, they took longer to complete the s e n t e n c e d e c i s i o n task c o m p a r e d to the letter tracing task, t (26) = -6.78, p < . 0 0 1 . Discussion T h e main p u r p o s e of the experiment w a s to investigate w h e t h e r the method d e s c r i b e d by B r o o k s (1968) provided a reliable a n d valid m e a n s for revealing the different types of attention. Participants w e r e required to perform two t a s k s concurrently. T h e y w e r e e n g a g e d in a task that required primarily visuo-spatial (categorizing corners of a block letter) or verbal r e s o u r c e s (categorizing w o r d s in a s e n t e n c e ) , a n d they indicated their a n s w e r s in a m a n n e r that required verbally, motor or visuo-spatial resources. T h e g e n e r a l pattern of results found in this experiment w a s consistent with my h y p o t h e s e s . C o m p l e t i o n time w a s the greatest w h e n participants handled two t a s k s that required the s a m e r e s o u r c e s . T h e results s h o w e d that r e s p o n d i n g in a verbal m a n n e r w a s s l o w e s t while categorizing w o r d s in a s e n t e n c e , a n d pointing to the a n s w e r s on a monitor w a s s l o w e s t for categorizing corners of a letter. C o m p l e t i o n time for tapping the a n s w e r s o n a k e y b o a r d w a s approximately the s a m e while c o m b i n e d with either input task, s u g g e s t i n g that tapping a n s w e r s required neither visuo-spatial nor verbal resources. 44  H o w e v e r , there are s e v e r a l differences between the results obtained from this experiment a n d the results reported by B r o o k s (1968). In this experiment, participants took 15 s to c o m p l e t e the s e n t e n c e d e c i s i o n task w h e n pointing to the a n s w e r s , while the completion time w a s slightly shorter (10 s) in the original study. T h e greater completion time found in this experiment c a n be e x p l a i n e d by the different technique u s e d record to the r e s p o n s e s . W h i l e B r o o k s (1968) required participants to circle the a n s w e r s on a p i e c e of paper, I required participants to u s e a m o u s e a n d select their a n s w e r s on a computer. Participants m a y have b e e n l e s s familiar with the m o u s e and computer method than the typical pencil a n d p a p e r m e t h o d , a n d this m a y explain why the completion time w a s greater in the present experiment. In the original study, participants took almost twice a s long to tap the a n s w e r s for the letter tracing task (M = 14.1 s, SD = 5.4) c o m p a r e d to the s e n t e n c e d e c i s i o n task (M = 7.8 s, SD = 2.1) while I found that completion time w a s approximately the s a m e for both letter tracing (M = 12.85, SD = 3.57) and s e n t e n c e d e c i s i o n task (M = 11.64, S D = 3.54). T h e effect s i z e for the m e a n difference in completion times for B r o o k ' s study is d = 1.54) a n d d = 0.34 for the m e a n difference in completion times for Experiment 3. O n c e a g a i n , the difference in m e a n completion times found in B r o o k ' s study a n d my experiment m a y be e x p l a i n e d by the method u s e d to record the r e s p o n s e s . In the original study, B r o o k s recorded the a n s w e r s by having participants touch either the Y or N printed o n a p i e c e of p a p e r for their r e s p o n s e s . Participants w e r e likely reading the Y or N prior to touching the a n s w e r . T h u s , the r e s p o n s e record method w a s likely to require s o m e visuo-spatial r e s o u r c e s , which resulted in greater completion time for performing the letter tracing task. Finally, a m u c h larger difference in completion time w a s found in this experiment between the letter tracing a n d s e n t e n c e d e c i s i o n t a s k s w h e n participants r e s p o n d e d by 45  saying the a n s w e r s c o m p a r e d to what w a s reported by B r o o k s (1968). Specifically, in this experiment, a n eight s e c o n d difference w a s found b e t w e e n the two input t a s k s (d = 1.66), while the original study found only a two s e c o n d difference between the s a m e tasks (d = .77). T h e difference in completion times a n d effect s i z e s m a y be explained by the i n c r e a s e d n u m b e r of participants in the study, which m a y reflect a more accurate understanding of the specific type of p r o c e s s i n g required for t h e s e t a s k s .  46  Experiment 4 T h e objective of this experiment w a s to explore the type of attention required of two P D A task t y p e s : Navigation a n d data entry. T h e dual task methodology w a s u s e d to a p p r o a c h this objective. T h e input t a s k s validated in E x p e r i m e n t 3 (letter tracing task a n d s e n t e n c e d e c i s i o n task) w e r e u s e d a s the s e c o n d a r y t a s k s . Participants were required to perform either a letter tracing task or a s e n t e n c e d e c i s i o n task concurrently with either a navigation or data entry task on the P D A . Method Participants Thirty undergraduate students were recruited through the subject pool in the p s y c h o l o g y department at the University of British C o l u m b i a . T h e y w e r e c o m p e n s a t e d with o n e c o u r s e credit in return for their participation. T h e experiment w a s conducted with the approval of the University of British C o l u m b i a behavioral ethics review board. Apparatus T h e s a m e a p p a r a t u s w a s u s e d a s in Experiment 1. Input T a s k s T h e letter tracing task a n d s e n t e n c e d e c i s i o n task w e r e u s e d a s the s e c o n d a r y t a s k s . T h e stimuli for the t a s k s , a s well a s the setup for the t a s k s are d e s c r i b e d in the M e t h o d s section of E x p e r i m e n t 3. Output T a s k s Participants r e s p o n d e d in o n e of two methods: verbally s a y i n g the a n s w e r s or tapping the a n s w e r s . T h e s e m e t h o d s of r e s p o n s e are d e s c r i b e d in the M e t h o d s section of Experiment 3.  47  P D A Tasks S i x t e e n P D A t a s k s w e r e s e l e c t e d , two per condition (a factorial combination of input task, output task a n d P D A task type yielded eight conditions). Eight t a s k s required s e a r c h i n g through the m e n u layers to find information (find font s i z e , retrieve appointments, c h e c k the battery, find voice m e s s a g e , create n e w folder, find Bluetooth version, find t h e m e s , a n d load w e b p a g e ) , a n d eight t a s k s required entering data. T w o of the navigation t a s k s w e r e identical to the o n e s u s e d in Experiment 1 (check the battery, retrieve appointments) and o n e of the navigation task w a s the s a m e o n e u s e d in E x p e r i m e n t 2 (find voice m e s s a g e ) . B e l o w includes a brief description of e a c h navigation task. Find font size. T h e instructions for this task directed participants to find the font size that d i s p l a y s the text o n the P D A . Create new folder F o r this task, participants w e r e required to find the program that had the option to create a new folder. Find Bluetooth version. T h i s task required participants to find the Bluetooth application a n d to display the current version of the application. Find themes. Participants w e r e instructed to find the s c r e e n that s h o w e d the available t h e m e s of the d e v i c e . Load a webpage. F o r this task, participants w e r e instructed to locate the s a v e d w e b p a g e w w w . h o t m a i l . c o m under the Favorites category a n d to load this w e b p a g e . T h e information for the data entry task c o n s i s t e d of eight f a m o u s English a p h o r i s m s , e a c h o n e s e n t e n c e in length. T h e s e n t e n c e s ranged from 31 to 35 p r e s s e s , five to s e v e n syllables a n d five to s e v e n words. Participants entered o n e s e n t e n c e for e a c h data entry task. E a c h of the P D A t a s k s c a n be c o m p l e t e d in a n u m b e r of different  48  w a y s . T a b l e 4 s h o w s the n u m b e r of number of s t e p s required for completing e a c h in the most efficient or optimal manner. Table 4 Design T h e d e s i g n of this experiment c o n s i s t e d of a 2 x 2 x 2 that had input task (letter tracing task, s e n t e n c e d e c i s i o n task), output task (tapping, saying) a n d P D A task (navigation, data entry) a s the within subjects factors. Procedures I tested participants individually in a s e s s i o n that lasted 60 minutes. U p o n obtaining their written c o n s e n t , e a c h participant c o m p l e t e d the t a s k s d e s c r i b e d below. E a c h participant c o m p l e t e d eight conditions in this experiment. E a c h condition consisted of a set P D A t a s k s listed in T a b l e 4 c o m b i n e d with a n input task and an output task. T h e eight conditions w e r e presented in a c o u n t e r b a l a n c e d order by m e a n s of a complete Latin S q u a r e d e s i g n . Prior to beginning e a c h condition, participants w e r e given two practice trials to familiarize t h e m with the input task. Specifically, participants w e r e given detailed instructions for how to c o m p l e t e the s e c o n d a r y task a n d the p r o c e d u r e s for the method of r e s p o n s e . T h e s e instructions w e r e the s a m e a s E x p e r i m e n t 3 a n d are d e s c r i b e d in the P r o c e d u r e s section of E x p e r i m e n t 3. T h e s e q u e n c e of e v e n t s for e a c h trial is a l s o d e s c r i b e d in the P r o c e d u r e s section in Experiment 3. Participants then c o m p l e t e d the P D A t a s k s listed in T a b l e 4 together with an input task (i.e., letter tracing task, s e n t e n c e d e c i s i o n task) a n d method of r e s p o n s e for the s e c o n d a r y task (i.e., tapping, saying). I instructed participants to f o c u s on completing the P D A t a s k s accurately a n d quickly, but to m a k e r e s p o n s e s for the input task w h e n e v e r p o s s i b l e . 49  Before participants started e a c h P D A task, I g a v e a verbal explanation of the goal of e a c h task. F o r navigation t a s k s , I s h o w e d participants a written description of the task a n d e x p l a i n e d the goal of the task. I removed the written material from view o n c e participants indicated that they understood the task. F o r data entry t a s k s , participants were first provided with the s e n t e n c e of the to-be-entered information. Next, I a s k e d participants to recite the s e n t e n c e to e n s u r e that they w e r e a b l e to r e h e a r s e the material from memory. I corrected any incorrect words recited by the participant. After correcting the participants, I a s k e d t h e m to repeat the complete s e n t e n c e a g a i n . W h e n participants were able to recite the s e n t e n c e perfectly, I r e m o v e d the materials with the written sentence. T h e p r o c e d u r e s for starting a n d ending the letter tracing a n d s e n t e n c e d e c i s i o n task w e r e the s a m e a s in Experiment 3 a n d are d e s c r i b e d in the P r o c e d u r e s section of Experiment 3. T h e p r o c e d u r e s for recording participant interactions with the P D A were the s a m e a s in E x p e r i m e n t 1 a n d are d e s c r i b e d in the P r o c e d u r e s section of Experiment 1. Following the completion of the last condition, participants w e r e given a verbal debriefing, a s well a s a written debriefing form, and a c o u r s e credit. Results Data Preparation T h e c o d i n g m a n u a l for the P D A t a s k s w a s d e v e l o p e d in the s a m e w a y a s in Experiment 1. T h e method for coding P D A task performance w a s s a m e a s in Experiment 1. P e r f o r m a n c e for the concurrent t a s k s w a s c a l c u l a t e d in the s a m e w a y a s in Experiment 3. I e x a m i n e d the d a t a from the input t a s k s a n d corrected for c o d i n g errors until a c c u r a c y w a s greater than 9 9 % . T h e results from the input t a s k s a n d P D A tasks w e r e 50  s c r e e n e d for univariate outliers, defined a s a s c o r e falling more than three standard deviations a w a y from the s a m p l e m e a n . N o outliers w e r e found from the input t a s k s . T h r e e outliers w e r e found from the P D A task data. E a c h outlier w a s r e p l a c e d with a non-outlying v a l u e , a n u m b e r either 3 standard deviations a b o v e or below the s a m p l e m e a n , respectively. T w e l v e participants did not complete at least a single trial on the concurrent t a s k s while they w e r e performing either the data entry or navigation t a s k s . T h e data from t h e s e participants w e r e e x c l u d e d from the a n a l y s i s . D a t a from the remaining 18 participants w e r e u s e d for the a n a l y s e s . P D A Tasks T h e d e p e n d e n t m e a s u r e s for the P D A t a s k s w e r e the p e r c e n t a g e of correct p r e s s e s , a n d the p e r c e n t a g e of errors for data entry a n d navigation t a s k s , s p e e d of data entry, a n d the a m o u n t of time to complete navigation t a s k s . Overall, two-thirds of the p r e s s e s in navigation t a s k s w e r e correct {M = 62.04). T h e p e r c e n t a g e of P D A t a s k s errors a s a function of input task, output task, a n d P D A task type are s h o w n in Figure 1 1 . O v e r a l l , error rates for navigation t a s k s were similar w h e n c o m b i n e d with either the letter tracing task (M = 40.41) or s e n t e n c e d e c i s i o n task (M = 44.33). H o w e v e r , error rates for navigation t a s k s varied a c r o s s the input task a n d the output task. W h e n concurrently performing the letter tracing or s e n t e n c e d e c i s i o n task, error rates for navigation t a s k s w e r e greater while m a k i n g motor r e s p o n s e s (M = 47.63) c o m p a r e d to v o c a l r e s p o n s e s (M = 37.11). H o w e v e r , this difference w a s greater w h e n c o m b i n e d with the letter tracing task a s c o m p a r e d to the s e n t e n c e d e c i s i o n task. Participants m a d e a greater percentage of errors while concurrently performing the letter tracing task w h e n m a k i n g motor r e s p o n s e s {M = 4 7 . 3 6 , S D = 20.34) c o m p a r e d to w h e n m a k i n g v o c a l r e s p o n s e s (M = 3 3 . 4 5 , S D = 19.72). W h e n c o m b i n e d with the 51  s e n t e n c e d e c i s i o n task, errors from the navigation t a s k s w e r e only slightly w h e n making motor r e s p o n s e s {M = 4 7 . 9 0 , S D = 15.88) c o m p a r e d to m a k i n g v o c a l r e s p o n s e s (M = 4 0 . 7 7 , S O = 16.44). Figure 11 A n in-depth e x a m i n a t i o n of the error rates for navigation t a s k s revealed that the percentage of errors ranged from 2 8 . 2 3 % ( S D = 28.42) to 5 7 . 1 6 % ( S D = 26.00). Participants m a d e the most errors w h e n finding the t h e m e s in the P D A , followed by finding the font s i z e (M = 5 5 . 4 2 , S D = 22.18), creating a n e w folder (M = 4 7 . 9 5 , S D = 20.21), finding the Bluetooth version (M = 4 7 . 8 4 , S D = 22.30), finding the appointment date (M = 3 9 . 3 1 , S D = 26.22), finding the voice m e s s a g e (M = 3 7 . 1 1 , S D = 24.47), finding the battery (M = 3 0 . 3 0 , S D = 25.88), a n d loading a w e b p a g e . T h e majority of p r e s s e s while entering data w e r e correct (M = 87.00). O v e r a l l , the percentage of data entry errors were similar w h e n concurrently performing a letter tracing task (M = 11.96) or s e n t e n c e d e c i s i o n task (M = 14.44). Participants m a d e a slightly greater p e r c e n t a g e of errors in data entry t a s k s while concurrently performing the letter tracing task a n d m a k i n g v o c a l r e s p o n s e s {M = 12.24, S D = 4.84) c o m p a r e d to w h e n making motor r e s p o n s e s (M = 11.69, S D = 6.72). Similarly, participants m a d e a slightly greater p e r c e n t a g e of errors for the s e n t e n c e d e c i s i o n task w h e n making v o c a l r e s p o n s e s (M = 15.42, S D = 8.29) c o m p a r e d to w h e n m a k i n g motor r e s p o n s e s (M = 13.47, S D = 7.39). Error rates for the data entry t a s k s ranged from 1 0 . 4 5 % ( S D = 8.69) to 1 7 . 0 4 % ( S D = 11.58). Participants m a d e the most errors while entering ' c h a n c e s favors the prepared mind', followed by entering 'don't bite the hand that f e e d s y o u ' (M = 15.92, S D = 18.22), 'all things c o m e to him w h o waits' (M = 14.27, S D = 9.38), 'birds of a feather  52  flock together' (M = 13.16, S D = 8.60), 'a rolling stone gathers no m o s s ' (M = 12.93, S D = 7.58), 'look on the s u n n y side of life' (M = 12.67, S D = 7.46), 'every cloud h a s a silver lining' {M = 11.36, S D = 6.42), a n d 'good f e n c e s m a k e g o o d neighbors'. A n A N O V A c o n d u c t e d on the error steps data with the input task, output t a s k s a n d P D A task a s the within-subject factors revealed a significant main effect of P D A task, F (1, 17) = 1 0 7 . 9 0 , MSE = 2 8 3 . 8 5 , p < .05, / = 2.44, s u c h that participants m a d e a significantly greater p e r c e n t a g e of errors in navigation t a s k s c o m p a r e d to data entry tasks. A two-way interaction w a s found between output task a n d P D A task, F (1, 17) = 5.66, MSE = 2 2 0 . 2 3 , p < .05, / = 0.51. Follow-up tests using a Bonferroni correction were c o n d u c t e d to explore the differences in p e r c e n t a g e of errors. F o r navigation t a s k s , participants m a d e a significantly greater percentage of errors while indicating their a n s w e r s for the input task by tapping c o m p a r e d to by s a y i n g . N o other differences were significant. T y p i n g s p e e d ranged from 4.28 W P M ( S D = 1.49) to 8.20 W P M ( S D = 4.19). Typing rate w a s the quickest for ' E v e r y cloud has a silver lining', followed by 'Birds of a feather flock together' (M = 7.43, S D = 2.66), ' G o o d f e n c e s m a k e g o o d neighbors' {M = 7.21, S D = 2.38), ' A rolling stone gathers no m o s s ' (M = 6.87, S D = 1.99), ' L o o k on the bright side of things' {M = 6 . 1 1 , S D = 3.63), 'Don't bite the h a n d that f e e d s y o u ' {M = 5.42, S D = 1.80), 'All things c o m e to him w h o waits' {M = 5.18, S D = 1.53), and ' C h a n c e favors the prepared mind'. T h e s u m m a r y of typing rate by the input task and output task is s h o w n in Figure 12. T y p i n g rate w a s slightly slower while participants were concurrently performing the s e n t e n c e d e c i s i o n task (M = 5.23) c o m p a r e d to the letter tracing task (M = 7.42). Figure 12  53  A n A N O V A c o n d u c t e d o n the typing s p e e d data from the data entry t a s k s with the input task a n d output task a s within-subject factors r e v e a l e d a significant main effect of input task, F (1, 17) = 2 3 . 2 8 , MSE = 3.73, p < . 0 0 1 , / = 1.11, s u c h that typing s p e e d w a s slower while concurrently performing a s e n t e n c e d e c i s i o n task. A significant interaction w a s a l s o f o u n d , F (1, 17) = 11.46, MSE = 5.16, p < .05, / = 0.48. Follow-up tests using a Bonferroni correction w e r e conducted to explore the differences in the typing s p e e d a c r o s s conditions. O v e r a l l , typing s p e e d while performing the s e n t e n c e d e c i s i o n task w a s significantly slower than concurrently performing the letter tracing task. In addition, typing s p e e d w a s significantly s l o w e r for the s e n t e n c e d e c i s i o n task w h e n r e s p o n d i n g vocally c o m p a r e d to tapping the a n s w e r s . C o m p l e t i o n times ranged from 4 0 . 2 2 s ( S D = 32.45) to 9 4 . 6 7 s ( S D = 57.70). Participants took the longest while trying to find the option to c h a n g e the font size, followed by creating a n e w folder (M = 8 8 . 5 6 , S D = 24.86), finding the available interface t h e m e s (M = 8 7 . 7 8 , S D = 52.03), finding the v e r s i o n of the Bluetooth (M = 77.39, S D = 38.09), finding a v o i c e recording (M = 6 9 . 9 4 , S D = 50.00), finding the battery status (M = 6 1 . 7 1 , S D = 44.02), finding the appointment date (M = 58.56, S D = 34.32), a n d loading a w e b p a g e . O v e r a l l , completion time for navigation t a s k s w a s greater w h e n participants concurrently performed the s e n t e n c e d e c i s i o n task (M = 73.49) c o m p a r e d to the letter tracing task (M= 66.61). A s s h o w n in Figure 13, completion time w a s greatest w h e n participants performed the S e n t e n c e D e c i s i o n task by tapping the r e s p o n s e s (M = 8 2 . 9 7 , S D = 21.17). C o m p l e t i o n times w e r e similar in the three other conditions. Figure 13  54  A n A N O V A w a s c o n d u c t e d on the completion time data from navigation t a s k s with the input task a n d output task a s the within-subject factors. T h e results revealed no significant effects. Secondary T a s k s C o m p l e t i o n time for the letter tracing a n d s e n t e n c e d e c i s i o n task a s a function of input task, output task, a n d P D A task type is s h o w n in Figure 14. Overall, participants took slightly longer to c o m p l e t e the s e n t e n c e d e c i s i o n task (M = 28.20) c o m p a r e d to the letter tracing task (M = 26.03). W h i l e performing a navigation task, completion time for the letter tracing task w a s slightly greater (M = 28.61) c o m p a r e d to the s e n t e n c e decision (M = 27.64). W h i l e performing a data entry task, completion time for the s e n t e n c e d e c i s i o n task w a s greater (M = 28.77) c o m p a r e d to the letter tracing task (M = 23.45). Figure 14 A n A N O V A w a s c o n d u c t e d on the completion time data with the input task, output task a n d P D A task type a s the within-subject factors. T h e results revealed a significant main effect of output task, F (1, 17) = 4 . 9 3 , MSE = 9 8 . 4 3 , p < .05, / = 0.47. A significant two-way interaction w a s found between input task by output task, F (1, 17) = 11.54, MSE = 6 0 . 5 2 , p < .05, / = 0.77, and input task by P D A task type, F (1, 17) = 4.52, MSE = 7 8 . 8 2 , p < .05, / = 0.44. N o other main effects or interactions were significant. Follow-up tests using a Bonferroni correction w e r e c o n d u c t e d to explore the differences in the completion times a c r o s s conditions. T h e s e n t e n c e d e c i s i o n task a n d tapping w a s significantly quicker than by tapping. C o m p l e t i o n time w a s significantly greater w h e n participants performed the letter tracing task a n d navigation t a s k s .  55  C o m p l e t i o n time w a s greater w h e n participants c o m b i n e d the s e n t e n c e d e c i s i o n task with data entry t a s k s c o m p a r e d to navigation t a s k s , but the difference w a s not significant. Discussion T h e primary objective of Experiment 4 w a s to explore the types of attention, required by navigation a n d data entry t a s k s . W e required participants to perform a s e c o n d task that either required visuo-spatial (i.e., letter tracing task) or auditory/articulatory (i.e., s e n t e n c e d e c i s i o n task) r e s o u r c e s in combination with a data entry or navigation task. A s w a s found in Experiment 1 and 2, the overall error rates for navigation tasks were greater than data entry t a s k s . H o w e v e r , performance for the P D A t a s k s from this experiment w a s w o r s e than what w a s found in E x p e r i m e n t 1 a n d 2. Participants m a d e a greater p e r c e n t a g e of errors for both navigation a n d data entry t a s k s , entered data at a slower rate, a n d took longer to find the target s c r e e n for navigation t a s k s . C o m p l e t i o n time for the input t a s k s (i.e., letter tracing task, s e n t e n c e decision task) by output t a s k s (i.e., s a y i n g , tapping) revealed the s a m e patterns a s in Experiment 3. C o m p l e t i o n time for the letter tracing task did not differ w h e t h e r participants indicated their a n s w e r s by tapping or calling out the a n s w e r s . T h e completion time for the s e n t e n c e d e c i s i o n task w a s greater w h e n participants indicated their r e s p o n s e s by saying the a n s w e r s than by tapping out the a n s w e r s . T h e s e findings are consistent with previous notions that tapping the a n s w e r s is primarily a motor activity, a n d thus should not interfere with p r o c e s s i n g with either input task, while s a y i n g the a n s w e r s requires mainly articulatory/auditory r e s o u r c e s . F o r navigation or data entry t a s k s , the error rates did not differ while performing the letter tracing task or the s e n t e n c e d e c i s i o n task. T h e differences in P D A task error 56  rates were revealed by the combination of input a n d output task. Navigation error rates were significantly higher w h e n participants were a s k e d to indicate their r e s p o n s e s by tapping the a n s w e r s c o m p a r e d to saying the a n s w e r s , but the difference w a s quite small. T h e o p p o s i t e w a s found for data entry t a s k s . F o r both the letter tracing a n d s e n t e n c e d e c i s i o n task, participants m a d e a greater p e r c e n t a g e of data entry errors while r e s p o n d i n g vocally c o m p a r e d to tapping the a n s w e r s . H o w e v e r , none of the data entry error rates a c r o s s conditions w e r e significantly different. Overall, typing s p e e d w a s slower while performing the s e n t e n c e d e c i s i o n task c o m p a r e d to the letter tracing task. Moreover, typing s p e e d w a s slightly slower while performing the s e n t e n c e d e c i s i o n task a n d responding vocally c o m p a r e d to responding by tapping. H o w e v e r , n o n e of t h e s e differences w e r e statistically different. T h e s e findings s u g g e s t that the slower typing rate is a result of the d e m a n d s placed on the auditory/articulatory r e s o u r c e w h e n performing data entry a n d concurrently making verbal r e s p o n s e s . O n e of the p o s s i b l e r e a s o n s for the elevated error rates, greater completion times a n d s l o w e r typing s p e e d s for the P D A t a s k s is the greater r e s o u r c e d e m a n d s for the letter tracing a n d s e n t e n c e d e c i s i o n task, c o m p a r e d to a tone discrimination task. T h i s is u n d e r s t a n d a b l e s i n c e the letter tracing a n d s e n t e n c e d e c i s i o n task required m u c h more r e s o u r c e s at any moment c o m p a r e d to a tone discrimination task. Performing tone discrimination simply requires the participant to attend to and to c o m p a r e whether the previously presented tone a n d the present tone s o u n d different. T h e r e s p o n s e is a binary d e c i s i o n , either the tones are the s a m e or they are not the s a m e . W h e r e a s for the input t a s k s in this experiment, participants w e r e required to first hold in mind the stimuli (e.g., a picture of the letter or the w o r d s in the s e n t e n c e ) , then retrieve the categorization instructions, a n d finally m a k e categorization judgements. 57  T h u s the elevated P D A error rates c a n be partly attributable to the fact that performing the concurrent t a s k s by itself is fairly difficult. C o m p l e t i o n times for the s e c o n d a r y t a s k s varied a s a function of the output task. T h e most prominent effect c a n be s e e n w h e n participants w e r e performing the s e n t e n c e decision task. C o m p l e t i o n time w a s greater w h e n participants indicated their r e s p o n s e s by saying the a n s w e r s c o m p a r e d to tapping their a n s w e r s o n a k e y b o a r d . This finding is consistent with the notion that categorizing w o r d s in a s e n t e n c e a n d indicating r e s p o n s e s verbally both require auditory/articulatory r e s o u r c e s . T h e critical results that are pertinent to the objective of this experiment are the completion time for the s e c o n d a r y t a s k s w h e n c o m b i n e d with the P D A t a s k s . T h e results revealed that data entry requires more auditory/articulatory r e s o u r c e s , while navigation requires both visuo-spatial a n d auditory/articulatory r e s o u r c e s , but more of the former.  58  General Discussion T h e overall g o a l of this thesis w a s to investigate the attentional d e m a n d s of various P D A t a s k s . T o a c h i e v e this g o a l , I u s e d s e v e r a l a p p r o a c h e s . T h e first a p p r o a c h w a s to validate a modified v e r s i o n of the dual-task methodology to a s s e s s the amount of attentional d e m a n d s of the P D A t a s k s . T h e s e c o n d a p p r o a c h w a s to explore the amount of attention required by the P D A t a s k s within the dual-task methodology framework. T h e third a p p r o a c h w a s to validate two t a s k s that w o u l d reveal the different types of attention. T h e fourth a p p r o a c h w a s to explore the types of attention required by t h e s e P D A t a s k s using the dual-task methodology with the t a s k s validated in the third a p p r o a c h . T h e main findings of t h e s e four a p p r o a c h e s w e r e d i s c u s s e d in Experiments 1 through 4, a n d will be briefly s u m m a r i z e d here. T h e implications for d e s i g n will be d i s c u s s e d , followed by limitations a n d directions for future r e s e a r c h . Summary of Research Findings T h e first a p p r o a c h towards achieving the goal of this t h e s i s w a s to explore the attentional d e m a n d s of navigation and data entry t a s k s using a dual-task methodology d e v e l o p e d for this p u r p o s e . T h i s a p p r o a c h forms the investigation reported in Experiment 1. U s i n g the tone discrimination task a s the s e c o n d a r y task, the results revealed that p e r f o r m a n c e for the tone discrimination task w a s lower w h e n concurrently completed with the navigation t a s k s c o m p a r e d to data entry t a s k s . T h e results reported in Experiment 1 were followed up in E x p e r i m e n t 2 in order to clarify w h e t h e r the d e v e l o p e d methodology a s s e s s e d the attentional d e m a n d s or the difficulty of task switching. A n e w level of difficulty w a s a d d e d to the tone discrimination task (i.e., e a s y a n d hard) that would manipulate the required attention for the tone discrimination task, but not the difficulty of switching b e t w e e n tone discrimination and a P D A task. T h e pattern of results from the tone discrimination task revealed that the 59  methodology a s s e s s e d attention. B a s e d on t h e s e findings, it w a s s u g g e s t e d that navigation requires more attention than data entry. In an investigation to find out whether navigation a n d d a t a entry t a s k s requires different types of attention, w h i c h forms the b a s i s of E x p e r i m e n t 3 a n d 4, I first validated a method d e s c r i b e d by B r o o k s (1968) w h i c h m a y be u s e d to reveal the types of attention. T h e results s u g g e s t e d that the method revealed two t a s k s that drew on visuospatial or auditory/articulatory r e s o u r c e s . U s i n g the dual-task methodology in Experiment 4 , I had participants complete a P D A task concurrently with o n e of the t a s k s validated in E x p e r i m e n t 3 in order to find out whether different types of attention w e r e required for the P D A t a s k s . T h e findings revealed that data entry drew heavily articulatory/auditory r e s o u r c e s , w h e r e a s navigation required both articulatory/auditory a n d visuo-spatial r e s o u r c e s , but more of the latter. General Limitations T h e r e are s e v e r a l limitations to the experiments reported in my thesis. First, all of the participants w e r e undergraduate students and m a y not be representative of the population, e s p e c i a l l y of older adults. T h e r e are s e v e r a l r e a s o n s w h y this is a c o n c e r n . First of all, attentional capacity, in addition with other cognitive abilities, has b e e n proposed to r e d u c e with a g i n g . S e c o n d , older adults are l e s s familiar with technology, a factor known to influence the attention required to u s e technology. D u e to both of these r e a s o n s , the s e c o n d a r y task d e c r e m e n t s are likely to reveal a larger effect with older adults than with u n d e r g r a d u a t e s . A s a result, caution must be taken w h e n generalizing the results of this study to a n older population. A s e c o n d limitation c o n c e r n s the r e s e a r c h d e s i g n of E x p e r i m e n t 2 and 4. Ideally, the d e s i g n s h o u l d a l s o h a v e included complete c o u n t e r - b a l a n c i n g of the combination of 60  P D A task sets with the conditions of the s e c o n d a r y task, s u c h that e a c h P D A task a p p e a r e d equally likely with e a c h combination of the conditions of the s e c o n d a r y task. T h u s , the findings are c o n f o u n d e d with both the intended manipulations from the experiments, a s well a s possibly the nature of the specific P D A t a s k s that were c o m b i n e d with e a c h of the conditions. In order to perform c o m p l e t e counter-balancing with the P D A task sets, I would require a total of 64 participants for Experiment 2, and 512 participants for E x p e r i m e n t 4. H o w e v e r , obtaining a s a m p l e of this size w a s not feasible during the c o u r s e of the a c a d e m i c year. Follow-up s t u d i e s in the near future c a n be c o n d u c t e d to i n c r e a s e the s a m p l e s to appropriate s i z e s for further investigation. For the moment, caution should be taken w h e n interpreting t h e s e results. T h e third limitation involves the input t a s k s u s e d in E x p e r i m e n t 4 . W h i l e the t a s k s were valid for a s s e s s i n g the types of attention required by the P D A t a s k s , I believe that the input t a s k s w e r e too difficult to be performed s i m u l t a n e o u s l y with the P D A t a s k s . T h e elevated p e r c e n t a g e of errors, greater completion times for navigation t a s k s , and slower typing s p e e d c o m p a r e d to Experiment 1 a n d 2 indicate that participants were having difficulty performing the P D A tasks well. T h i s finding m a y s u g g e s t that performing a input task a n d a P D A task w e r e simply too attention d e m a n d i n g , and found it difficult to maintain P D A task performance while trying to perform a input task. T o fully a s s e s s the type of attention required, another set of concurrent t a s k s m a y be n e e d e d . Finally, t e c h n o l o g y familiarity of the participants w a s not a s s e s s e d in t h e s e experiments. Familiarity of the task is known to influence the a m o u n t of attention required to perform the task. H o w e v e r , while t e c h n o l o g y familiarity within the undergraduate population is likely to differ a m o n g individuals, the variability should be quite s m a l l . In addition, at the time that t h e s e e x p e r i m e n t s w e r e c o n d u c t e d the d e v i c e w a s new a n d it w a s unlikely that participants had any e x p e r i e n c e in using this specific 61  device. T h i s r e a s o n i n g is supported by the small variability s e e n in the performance m e a s u r e s of the P D A t a s k s . H o w e v e r , a follow-up study that a l s o a s s e s s e s the technology familiarity would strengthen the validity of the findings. Implications for Design A s mentioned in the introduction, P D A s are frequently u s e d in various environments. T h u s , a n u m b e r of guidelines and principles c a n be implemented to e a s e the attentional d e m a n d s in order to facilitate efficiency a n d efficacy. First, to reduce the amount of attention p l a c e d on navigation, o n e of the s u g g e s t i o n s w o u l d be to reduce the n u m b e r of m e n u layers required to find the target s c r e e n . A c r o s s the experiments, trying to locate the E x c e l w o r k s h e e t w a s o n e of the t a s k s performed most efficiently a n d easily (i.e., least a m o u n t of time a n d errors). O n e of the p o s s i b l e r e a s o n s is that the E x c e l shortcut s h o w s up o n the Start m e n u after the first a c c e s s . T h u s , after pressing the Start m e n u , participants could easily recognize the option. F o r y o u n g e r adults w h e r e technology u s e is frequent a n d varied, this d e s i g n s u g g e s t i o n m a y be e v e n more effective for older u s e r s w h e r e technology familiarity is low. H o w e v e r , reducing the levels in the hierarchy m a y lead to interfaces with m a n y menu options, creating a n environment with too m a n y c h o i c e s that m a y overload attention. T h i s is e s p e c i a l l y true for P D A s , where s c r e e n s p a c e is limited a n d there is a trade-off with displaying the amount of information a n d the visual clarity of which the information c a n be v i e w e d . Therefore, it is important that the navigation structure is b a l a n c e d b e t w e e n depth a n d breadth, s o that the items in e a c h m e n u a n d number of steps that h a v e to be taken to complete a task are b a l a n c e d ( W e s t e r m a n , 1995). T h e r e is previous r e s e a r c h that d e m o n s t r a t e s that the organization of m e n u structures c a n influence attentional d e m a n d s . W e s t e r m a n , D a v i e s , G l e n d o n , S t a m m e r s and Matthews (1995) found that a linear information structure w a s beneficial for all a g e 62  groups, in terms of s e a r c h times. S t a n n e y & S a l v e n d y (1995) found that 2 D visual hierarchies (all levels visible) a n d linear structures (open folders with their files presented) w e r e more efficient in supporting individuals with low spatial ability than interfaces w h e r e s o m e parts of the information structure w e r e hidden (buttons presenting only main categories). B a s e d on t h e s e findings, interfaces that are rich in presenting the structure of the information s p a c e m a y r e m o v e the n e e d to mentally construct the environment, w h i c h in turn could be beneficial for individuals with low spatial ability ( S t a n n e y & S a l v e n d y , 1995; V i n c e n t e & W i l l i g e s , 1988). T h e s e c o n d r e c o m m e n d a t i o n c o n c e r n s the visual presentation of information. F r o m informal o b s e r v a t i o n s , I noticed that participants spent longer looking at s c r e e n s that d i s p l a y e d more icons a n d m e n u options than w h e n f e w e r options w e r e available. It is important that the u s e r is able to f o c u s the attention o n the task at h a n d . W h i l e e n g a g e d in multiple activities simultaneously, irrelevant information or cluttered b a c k g r o u n d s o n a c o m p u t e r s c r e e n c a n be distracting ( C o n n e l l y & H a s h e r , 1993). Interfaces with r e d u c e d information content m a k e it e a s i e r to f o c u s attention on relevant information a n d r e d u c e the time spent on information s e a r c h e r s . A i d in focusing attention c a n be provided by structuring the information, providing spatial and temporal c u e s , a n d manipulating the s c r e e n layout (Singh, 2 0 0 0 ; s e e P r e e c e , R o g e r s , B e n y o n Holland & C a r e y , 1994). P r e s e n t i n g information to various s e n s o r y c h a n n e l s c a n reduce the attentional load on o n e single s y s t e m . T h e capacity of the s e n s o r y s y s t e m limits the amount of information that c a n be learnt or a b s o r b e d . T a k i n g a d v a n t a g e of all the available s e n s o r y s y s t e m s by presenting information via different s y s t e m s c a n facilitate acquisition of k n o w l e d g e . F o r e x a m p l e , B r u n k e n , S t e i n b a c h e r , P l a s s a n d Leutner (2002) found that a u d i o v i s u a l presentation of text-based a n d picture-based learning materials 63  induced l e s s cognitive l o a d , a n d facilitated knowledge acquisition, c o m p a r e d to the visual-only presentation of the s a m e material. T a r d i e u a n d G y s e l i n c k (2003) investigated w h e t h e r the u s e of multimodal information presentation would reduce cognitive o v e r l o a d o n working m e m o r y by using the s u b s y s t e m s in working memory. Finally, providing environmental support might e n h a n c e learning a n d s u b s e q u e n t s e a r c h performance. Environmental support c o n s i s t s of information in the environment that facilitates e n c o d i n g or retrieval of information a n d c a n r e d u c e the amount of cognitive p r o c e s s i n g that is n e e d e d ( J o n e s & B a y e n , 1998). Navigation is effortful and attention d e m a n d i n g . O n e s u g g e s t i o n is to provide certain pop-up dialog b o x e s that m a y guide finding the task b a s e d o n the statistical probability of the most c o m m o n l y u s e d applications. H o w e v e r , it is a l s o important to c o n s i d e r whether or not the environmental support i n c r e a s e s the cognitive d e m a n d s to the point that it b e c o m e s too d e m a n d i n g . It is therefore important to investigate which type of support c o n s i d e r e d to be useful for different t a s k s , a n d to what extent individuals c a n m a k e u s e of the environmental support that is provided ( M c D o w d & S h a w , 2000). Future Directions A s d e s c r i b e d in the introduction, o n e of the primary motivations for conducting this line of r e s e a r c h is to understand the factors that affect usability of P D A s . T h e s e r i e s of experiments d e s c r i b e d in this thesis formed a s pilot studies to w h i c h the methods could be applied to a s s e s s the attentional d e m a n d s of P D A u s e a c r o s s the lifespan. O n e line of future r e s e a r c h c a n explore how attentional d e m a n d s of different P D A t a s k s c h a n g e a c r o s s the adult lifespan. T h e findings from the experiments in this thesis have s u g g e s t e d that navigation is more d e m a n d i n g than d a t a entry. F r o m what is known in the a r e a of cognitive a g i n g , aging is a s s o c i a t e d with l o s s of available r e s o u r c e s (Craik, 1 9 8 3 ; C r a i k & B y r d , 1982; R a b i n o w i t z , C r a i k & A c k e r m a n , 1982). 64  G i v e n t h e s e two p r e m i s e s , it would be r e a s o n a b l e to predict that P D A task performance would be w o r s e a m o n g older adults c o m p a r e d to y o u n g e r adults, w h i c h could be partly explained by the r e d u c e d attentional capacity from a g i n g . A l t h o u g h previous r e s e a r c h has led to the formulation of extensive d e s i g n guidelines for cell p h o n e interfaces, w e b p a g e s , and v a r i o u s software applications for the P C , there is no r e s e a r c h that specifically f o c u s e s o n reducing attentional load on P D A t a s k s . S i n c e P D A s relies on a different interaction t e c h n i q u e than a d e s k t o p or laptop c o m p u t e r (i.e., stylus a n d t o u c h s c r e e n ) , a n d h a s a different s c r e e n size than other technological d e v i c e s (such a s cell p h o n e s or p e r s o n a l c o m p u t e r s ) , it is r e a s o n a b l e to believe that the findings will yield something novel. A n o t h e r line of this type of r e s e a r c h is to investigate w h e t h e r aging has the s a m e effect on the different types of attentional r e s o u r c e s . At present, there is a lot of r e s e a r c h that indicates that aging affects spatial ability, but not verbal ability. In addition, there h a s b e e n no study that c o m p a r e s the two types of attention. O n e of the implications of this theoretical r e s e a r c h is to determine w h e t h e r to f o c u s innovative r e s e a r c h a n d d e s i g n guidelines to c h a n g e P D A t a s k s that take a d v a n t a g e of the ability that is less s u s c e p t i b l e to a g i n g . T h e other implication w o u l d be to c o m p l e m e n t interface and d e v i c e specifications with training. T h e third line of r e s e a r c h c a n explore whether older v e r s u s y o u n g e r adults are more c h a l l e n g e d by navigation than data entry t a s k s . In g e n e r a l , most studies that have investigated the effects of a g e on technology u s e have found that older adults typically m a k e more errors a n d take longer to complete the task c o m p a r e d to y o u n g e r adults on both data entry t a s k s (Brewster & Cryer, 1999; C z a j a , H a m m o n d , B l a s c o v i c h & S w e d e , 1989; C z a j a & Sharit, 1998) a n d information s e a r c h t a s k s . In a pilot study with individuals ranging from 18 to 8 5 y e a r s of a g e , w e found that older adults m a d e more 65  errors on navigation a n d data entry t a s k s , a n d took longer for navigation t a s k s c o m p a r e d to y o u n g e r adults (Graf & Li, 2007). H o w e v e r , it is u n c l e a r the specific nature of e a c h task that m a k e s t h e m more difficult to perform by older adults. Future studies c a n explore the specific factors that m a y contribute to the difficulty of the task.  66  Conclusion T h e results from the experiments of my thesis d e m o n s t r a t e d that navigation and data entry performed on a P D A differ in the amount of attention, a n d type of attention. T h e s e findings are consistent with the intuition that data entry is e a s i e r s i n c e it involves mostly a motor activity, w h e r e a s navigation requires a greater amount of cognitive p r o c e s s i n g , s u c h a s r e m e m b e r i n g what you n e e d to find, w h e r e you are in the s y s t e m , a n d the correct options that will lead to the desired application. T h e findings are a l s o consistent with the notion that data entry involves primarily r e h e a r s i n g the to-be-entered information while navigation requires creating a mental m o d e l of the m e n u s y s t e m . A s d i s c u s s e d in the introduction, performing these t a s k s under highly attention d e m a n d i n g environments m a y c o m p r o m i s e usability of certain t a s k s . T h e results from this thesis contribute to the theoretical understanding of the interaction b e t w e e n the attentional d e m a n d s of P D A t a s k s a n d the environment. T h i s u n d e r s t a n d i n g o p e n s up the possibilities of further r e s e a r c h that could be c o n d u c t e d to pinpoint the specific characteristics of t h e s e t a s k s that m a k e them attention d e m a n d i n g . T h e s e findings will have implications for the d e s i g n guidelines of P D A s a n d , a n d p e r h a p s , other technologies.  67  Table 1 The number of Optimal Steps/Presses for each P D A Task as an Indicator of Task Difficulty PDA Tasks  O r d e r of Tasks  N u m b e r of required s t e p s Navigation  Data entry  Total  C h e c k the battery  4  /  4  2  Retrieve appointments  6  /  6  4  Find a picture  4  /  4  5  Enter contact information  3  116  119  1  Enter e x p e n s e information  4  74  78  3  M a k e a n appointment  6  23  29  6  25  213  238  Navigation t a s k s  Data entry t a s k s  Total steps  68  Table 2 Percentage of Correct, Incorrect, and Adjusted Identifications in the Tone Discrimination Task a c r o s s Conditions Identification Test Score  Condition  Baseline  Correct Incorrect  Data Entry  M  CI.95  M  CI.95  M  CI.95  75.00  70.21, 79.79  48.10  39.73, 56.46  32.78  24.95, 40.61  9.50  5.43,  6.26  4.39,  9.31  5.85, 12.77  23.47  14.05, 32.90  13.56 Adjusted  Navigation  65.50  58.39, 72.61  8.12 41.84  32.78, 50.91  69  Table 3 The Number of Steps/Presses Required by each P D A Task across Tone Discrimination Task Difficulty N u m b e r of required s t e p s  PDA Tasks  Navigation  Data entry  Total  Find Picture  4  /  4  1  Retrieve Appt Information  6  /  6  2  C h e c k Battery  4  /  4  3  Enter S e n t e n c e s  4  88  92  1  Name New Folder  5  19  24  2  Enter C o n t a c t Information  3  116  119  3  Enter E m a i l M e s s a g e  4  36  40  1  Enter Appointment Information  6  23  29  2  Enter E x p e n s e Information  4  74  78  3  Find V o i c e R e c o r d i n g  5  /  5  1  Find E m a i l A d d r e s s  3  /  3  2  Find O w n e r  3  /  3  3  48  356  404  Easy Navigation  Easy Entry  Hard E n t r y  b  c  d  Total steps Set A SetB SetC SetD  3  b  c  Hard N a v i g a t i o n  a  Order within S e t s  d  70  Table 4 P e r c e n t a g e of C o r r e c t , Incorrect, a n d A d j u s t e d Identifications in the T o n e D i s c r i m i n a t i o n T a s k a c r o s s T a s k C o n d i t i o n s and Tone Discrimination Difficulty  dentification | Test Score j  Condition  j  Baseline Easy  M Correct  \  90.23 !  :  | Hard  ;  D a t a Entry  I  SE  SE  M  2.06  .J30.63 |  5.07  Incorrect  1.82  0.34  3.04  I  .74  Adjusted  88.42  2.13  i 57.59 !  5.62  Easy  M  |  , SE  :  53.09 |  5.49  ]  I  0.23  :  51.92 |  5.51  1.17  Hard  m  Navigation  j  |  43.94 |  j SE  |  Easy  M  \  [ SE  5.36  I 45.83  5.62  |  0.27  j  0.36  42.40 |  5.42  | 44.10  1.53  1.73  5.62  Hard  M  \  SE  !  5.07  !  !  0.41  |  26.96 j  5.14  |  28.86 | 1.91  ->J  Table 5 The number of Steps/Presses Required by each P D A Task A c r o s s Conditions N u m b e r of required s t e p s  O r d e r within S e t s  Find font s i z e  6  1  Retrieve appointments  5  2  C h e c k the battery  5  1  Find v o i c e m e s s a g e  4  2  C r e a t e new folder  5  1  Find Bluetooth v e r s i o n  5  2  Find t h e m e s available in d e v i c e  3  1  Load webpage  4  2  A rolling stone gathers no m o s s .  32  1  G o o d f e n c e s m a k e g o o d neighbors.  32  2  Birds of a feather flock together.  34  1  E v e r y cloud h a s a silver lining.  32  2  Look on the s u n n y s i d e of life.  31  1  All things c o m e to him w h o waits.  33  2  C h a n c e favors the prepared mind.  32  1  Don't bite the h a n d that f e e d s y o u .  35  2  Letter T r a c i n g / T a p p i n g / N a v i g a t i o n  Letter T r a c i n g / S a y i n g / N a v i g a t i o n  Sentence Decision/Tapping/Navigation  Sentence Decision/Saying/Navigation  Letter T r a c i n g / T a p p i n g / D a t a entry  Letter T r a c i n g / S a y i n g / D a t a Entry  S e n t e n c e D e c i s i o n / T a p p i n g / D a t a Entry  S e n t e n c e D e c i s i o n / S a y i n g / D a t a Entry  72  Image r e m o v e d d u e to copyright. V i e w original i m a g e at w w w . h p . c o m Figure 1. Picture of the d e v i c e u s e d for the experiment.  73  1400  w  1200  E (/> c o a a:  1000 isilPtSf  800  600 Baseline  Data entry  Navigation  Condition Figure 2. R e s p o n s e time (mean of median) for correct identification of target tones a c r o s s conditions. f  vertical bars represents 9 5 % c o n f i d e n c e intervals  74  •  40  Easy  • Hard 6^  S2  30  o k_ k.  UJ «*o 20 0)  U)  c o o 10 L. <D  Q.  D a t a Entry  Navigation P D A Task Type  Figure 3. P e r c e n t a g e of errors in data entry and navigation t a s k s a s a function of tone discrimination difficulty. 1  vertical bars r e p r e s e n t s standard errors  75  1100  _  1000  E E  900  a> (0  c o a. a:  800  700  tulip's  600 Baseline  Data entry  Navigation  Condition  Figure 4. R e s p o n s e time (mean of medians) of correct identifications in the tone discrimination task a s a function of tone discrimination difficulty a n d task conditions, f vertical bars represents standard errors  76  Figure 5. Stimuli for the practice trials of the letter tracing task.  77  5 Figure 6. Stimuli for the test trials of the letter tracing task.  78  time  respond  top/bottom  re 7. Illustration of a trial of the letter tracing task with top/bottom instructions.  Figure 8. Illustration of a trial of the letter tracing task with outside instructions.  80  N N N N N N N N N N N N Figure 9. Image of s t a g g e r e d Y a n d N of the output task (pointing).  81  30 El Letter Tracing task • S e n t e n c e D e c i s i o n task *  20  10  0 Pointing  Tapping  Saying  Output T a s k s Figure 10. M e a n completion time a s a function of input task a n d output task. +  vertical bars represent standard error.  82  • Saying • Tapping  Navigation  Data Entry  Letter Tracing task  Navigation  D a t a Entry  Sentence Decision Task  Figure 11. P e r c e n t a g e of P D A task errors a s a function of input task, output task, and P D A task type. * vertical bars represent standard error.  83  10 • Tapping —  • Saying  8  Q.  B  6  1  o Q.  V>  TJ k.  O  5  Letter Tracing task  S e n t e n c e D e c i s i o n task Task Type  Figure 12. T y p i n g s p e e d (words per minute) in data entry t a s k s a s a function of input task, a n d output task. t vertical bars represent standard error.  84  100 n Tapping _ w o  80  0)  60  O (A  E  • Saying  c o  1  40  Q.  E o °  20  Letter Tracing task  S e n t e n c e D e c i s i o n task Task T y p e  Figure 13. 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