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Reflexive and volitional orienting in children and adults : pointing to a new future Ristic , Jelena 2003

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REFLEXIVE A N D VOLITIONAL ORIENTING IN C H I L D R E N A N D ADULTS: POINTING TO A N E W FUTURE  by J E L E N A RISTIC . B.A., The U n i v e r s i t y of B r i t i s h C o l u m b i a , 2000  A THESIS SUBMITTED I N P A R T I A L F U L F I L M E N T O F THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF ARTS in T H E F A C U L T Y OF G R A D U A T E STUDIES ( D e p a r t m e n t of P s y c h o l o g y ; C o g n i t i v e Systems P r o g r a m ) W e accept this thesis as c o n f o r m i n g to the r e q u i r e d s t a n d a r d  T H E UNIVERSITY O F BRITISH C O L U M B I A J u l y 2003 © Jelena Ristic, 2003.  In presenting this thesis in partial fulfilment of the  requirements for  an advanced  degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for department  or  by his  or  scholarly purposes may be granted by the head of my her  representatives.  It  is  understood  that  copying or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department of The University of British Columbia Vancouver, Canada  DE-6 (2/88)  11  ABSTRACT T r a d i t i o n a l l y , v o l i t i o n a l attention has been s t u d i e d i n the P o s n e r c u i n g p a r a d i g m b y u s i n g central s p a t i a l l y p r e d i c t i v e a r r o w s as attentional cues. T h e i m p o r t a n t a s s u m p t i o n u n d e r l y i n g this m e t h o d o l o g y has b e e n that a r r o w s (and other central attentional cues) orient attention s p a t i a l l y o n l y if they p r e d i c t w h e r e the target is l i k e l y to appear. Recent studies, h o w e v e r , indicate that this f u n d a m e n t a l a s s u m p t i o n u n d e r l y i n g the classic m e t h o d o l o g y is m i s t a k e n . Several studies n o w report that a range of central d i r e c t i o n a l cues, i n c l u d i n g a r r o w s , can trigger reflexive o r i e n t i n g effects i n b o t h y o u n g c h i l d r e n a n d adults w h e n they d o not p r e d i c t w h e r e the target is l i k e l y to appear. T h i s fact raises the question of w h e t h e r past studies, u s i n g p r e d i c t i v e central a r r o w s as attentional cues, w e r e m e a s u r i n g (1) v o l i t i o n a l attention because the a r r o w s w e r e p r e d i c t i v e , (2) reflexive attention because the a r r o w s w e r e d i r e c t i o n a l , or (3) some c o m b i n a t i o n of v o l i t i o n a l a n d reflexive attention. T h i s issue w a s investigated i n t w o studies. T h e first s t u d y is p r e s e n t e d i n C h a p t e r 1. T h i s i n v e s t i g a t i o n tested adults w i t h (1) p r e d i c t i v e a r r o w cues (2) n o n p r e d i c t i v e a r r o w cues, to get a p u r e measure of reflexive o r i e n t i n g , a n d (3) p r e d i c t i v e n o n d i r e c t i o n a l cues, to get a p u r e m e a s u r e o f v o l i t i o n a l o r i e n t i n g . T h e results of this first s t u d y s h o w e d that the m a g n i t u d e of o r i e n t i n g o b s e r v e d w i t h p r e d i c t i v e a r r o w cues w a s a l w a y s larger t h a n the s u m of p u r e reflexive a n d v o l u n t a r y o r i e n t i n g , s u g g e s t i n g that the t r a d i t i o n a l m e a s u r e reflects a n interaction b e t w e e n reflexive a n d v o l i t i o n a l attention. T h e s e c o n d s t u d y , presented i n C h a p t e r 2, tested c h i l d r e n b e t w e e n the ages of 3 a n d 6 i n a c o n d i t i o n s c o m p a r a b l e to those i n the first s t u d y w i t h a d u l t s . T h e results s h o w e d that p u r e reflexive o r i e n t i n g w a s a d u l t - l i k e , b u t v o l i t i o n a l o r i e n t i n g w a s not. Y o u n g c h i l d r e n , u n l i k e adults, c o u l d sustain v o l i t i o n a l attention for o n l y a brief p e r i o d  Ill of time. M o r e o v e r , a n d also u n l i k e adults, reflexive a n d v o l i t i o n a l o r i e n t i n g a p p e a r e d to be a d d i t i v e rather t h a n interactive. It is suggested that c o l l e c t i v e l y these f i n d i n g s are consistent w i t h the fields' current u n d e r s t a n d i n g of the m a t u r a t i o n of b r a i n regions t h o u g h t to m e d i a t e reflexive and volitional orienting.  iv TABLE OF CONTENTS Abstract  ii  Table of C o n t e n t s  iv  L i s t of Tables  vi  L i s t of F i g u r e s  vii  Acknowledgements  viii  Dedication  ix  CHAPTER 1  1  Introduction  2  Experiment 1  7  Method  •  7  Participants  7  Apparatus and Stimuli  7  Design  9  A r r o w Cues  10  N u m b e r Cues  10  Procedure  11  Results  12  Discussion  17  E x p e r i m e n t 2.....  17  Method  18  Results  Participants  18  Apparatus, Stimuli, Design, and Procedure  18 19  v Discussion  22  General Discussion  22  References  25  CHAPTER 2  28  Introduction  29  Experiment 1  31  Method  32  Participants  32  Apparatus and Stimuli  33  Design  34  Procedure  35  Results  37  Discussion  42  References  45  vi LIST O F T A B L E S  CHAPTER 1 Table 1. M e a n response times, s t a n d a r d deviations, a n d error rates for E x p e r i m e n t 1  13  Table 2. M e a n response times, s t a n d a r d deviations, a n d error rates for E x p e r i m e n t 2  19  CHAPTER 2  '  Table 1. M e a n response times a n d s t a n d a r d d e v i a t i o n s for a d u l t s  37  Table 2. M e a n response times a n d s t a n d a r d d e v i a t i o n s for c h i l d r e n  38  Table 3. O v e r a l l error a n d eye m o v e m e n t rates  38  •.  vii LIST O F F I G U R E S  CHAPTER 1  F i g u r e 1. S a m p l e Sequence of Events  9  F i g u r e 2. E x p e r i m e n t 1 Results  14  F i g u r e 3. E x p e r i m e n t 2 Results  20  CHAPTER 2 F i g u r e 1. S a m p l e Sequence of E v e n t s  34  F i g u r e 2. E x p e r i m e n t 1 Results  39  Vlll  ACKNOWLEDGEMENTS I w o u l d l i k e to express sincere gratitude to m y s u p e r v i s o r A l a n K i n g s t o n e for the exceptional s u p p o r t he p r o v i d e d m e w i t h , b o t h o n a scientific a n d p e r s o n a l level. N e x t , m a n y thanks to Jatinder (Bobby) S i d h u for a l l the daycare trips; B o b b y ' s f r i e n d s h i p a n d p e r s o n a l sacrifice t r u l y m a d e the research c o n d u c t e d w i t h y o u n g c h i l d r e n (reported i n C h a p t e r 2) effortless a n d enjoyable. T h e research r e p o r t e d here w a s s u p p o r t e d b y graduate f e l l o w s h i p s f r o m the N a t u r a l Sciences a n d E n g i n e e r i n g Research C o u n c i l of C a n a d a ( N S E R C ) , the M i c h a e l S m i t h F o u n d a t i o n for H e a l t h Research ( M S F H R ) , a n d a U n i v e r s i t y of B r i t i s h C o l u m b i a g r a d u a t e a w a r d . A d d i t i o n a l s u p p o r t came f r o m grants a w a r d e d to A l a n K i n g s t o n e f r o m the H u m a n Frontiers Science P r o g r a m ( H F S P ) , N S E R C , a n d M S F H R .  to my parents Sonja and Pavle  1  CHAPTER 1  2 Introduction B e h a v i o r a l studies of covert spatial attention to date i n d i c a t e that t w o q u a l i t a t i v e l y different f o r m s of attentional o r i e n t i n g occur i n response to t w o different attentional cues (e.g., Posner, 1980; Jonides, 1981; M u l l e r & Rabbitt, 1989). Reflexive o r i e n t i n g occurs i n response to salient events i n the e n v i r o n m e n t . V o l i t i o n a l o r i e n t i n g , o n the other h a n d , is generated i n accordance w i t h a n observer's goals a n d expectations. T r a d i t i o n a l l y , b e h a v i o r a l m a r k e r s of reflexive o r i e n t i n g w e r e e x p e r i m e n t a l l y e x a m i n e d u s i n g a b r u p t u n e x p e c t e d p e r i p h e r a l events w h e r e a s the b e h a v i o r a l i n d e x of v o l i t i o n a l attention w a s e x a m i n e d b y m a n i p u l a t i n g central s p a t i a l l y i n f o r m a t i v e s y m b o l i c cues. I n the p e r i p h e r a l c u i n g task participants are t y p i c a l l y p r e s e n t e d w i t h brief l u m i n a n c e transients, s e r v i n g as attentional cues, a p p e a r i n g r a n d o m l y (p=. 5) i n one of the t w o p o s s i b l e target locations. The observers' task is to press a k e y w h e n the target appears o n the screen at one of these t w o locations. I n o r d e r to p r o f i l e t e m p o r a l characteristic of the target response, the time b e t w e e n the cue onset a n d the target onset is t y p i c a l l y v a r i e d ( S t i m u l u s Onset A s y n c h r o n y or S O A ) b e t w e e n 0 a n d 1000 m s . The results of s u c h a task generally indicate that targets a p p e a r i n g at the l o c a t i o n w h e r e the cue w a s p r e s e n t e d w i t h i n 0-300 m s are detected faster t h a n targets a p p e a r i n g at the n o n c u e d l o c a t i o n . H o w e v e r , w h e n the cue-target time d e l a y exceeds 300ms, the o p p o s i t e effect is seen: targets a p p e a r i n g at the u n c u e d l o c a t i o n n o w p r o d u c e faster response times (RTs) t h a n the targets a p p e a r i n g at the p r e v i o u s l y c u e d location. T h i s reversal of the attentional effect has b e e n labeled " I n h i b i t i o n of R e t u r n " (IOR), d e n o t i n g the i d e a that attention w a s i n i t i a l l y allocated to the c u e d l o c a t i o n (hence the shorter R T s early on) a n d is n o w b e i n g i n h i b i t e d i n r e t u r n i n g to the c u e d l o c a t i o n at l o n g e r S O A intervals (e.g., Posner, 1980; P o s n e r & C o h e n , 1984). T h i s b i p h a s i c R T p a t t e r n at the c u e d l o c a t i o n m a r k e d b y early R T facilitation f o l l o w e d b y I O R at l o n g e r cue-target delays has  3 t r a d i t i o n a l l y b e e n t h o u g h t to reflect the b e h a v i o r a l signature of a u t o m a t i c attentional o r i e n t i n g (e.g., R a f a l , C a l a b r e s i , B r e n n a n & Sciolto, 1989; P o s n e r & C o h e n , 1984). I n contrast, v o l i t i o n a l o r i e n t i n g is t h o u g h t to reflect c o n t r o l l e d rather t h a n a u t o m a t i c p r o c e s s i n g i n that it requires the d e v e l o p m e n t of a n expectancy set that is b a s e d o n the i n f o r m a t i o n p r o v i d e d b y the cue ( M u l l e r & Rabbitt, 1989; Jonides, 1981). A s s u c h , attentional cues t y p i c a l l y u s e d to elicit v o l i t i o n a l o r i e n t i n g m a n i p u l a t e internal expectations about a target's occurrence b y u s i n g m e a n i n g f u l s y m b o l i c s t i m u l i for d i r e c t i n g attention (e.g., Jonides, 1981). In this task, p a r t i c i p a n t s are a s k e d to fixate a central a r r o w cue that has p r e d i c t i v e v a l u e a b o u t a target's occurrence. T h a t is, the target appears at the l o c a t i o n i n d i c a t e d b y a r r o w d i r e c t i o n o n 80% of a l l the trials. The task is to detect the target a p p e a r i n g either at the c u e d or l i k e l y l o c a t i o n (p=. 8) or at the u n c u e d or u n l i k e l y l o c a t i o n (p=. 2). The results s h o w that targets a p p e a r i n g at the l i k e l y l o c a t i o n are a l w a y s detected faster t h a n targets a p p e a r i n g at a n u n e x p e c t e d location w i t h the effect i n c r e a s i n g a n d r e a c h i n g a n a s y m p t o t e at a p p r o x i m a t e l y 500ms S O A ( M u l l e r & Rabbitt, 1989; Jonides, 1981). T h e differences i n the b e h a v i o r a l i n d e x of reflexive a n d v o l i t i o n a l attention m o v e m e n t s h a v e suggested that this d i c h o t o m y m a y not reflect differences i n allocation of resources w i t h i n a single attentional m e c h a n i s m (Posner, 1980; Jonides, 1981). A s s u c h , it w a s suggested that reflexive a n d v o l i t i o n a l attention operate i n a n a d d i t i v e f a s h i o n w i t h a u t o m a t i c (reflexive) a n d c o n t r o l l e d (volitional) attentional b e i n g d i f f e r e n t i a l l y susceptible to m a n i p u l a t i o n s of c o g n i t i v e l o a d a n d expectancy i n f o r m a t i o n (e.g., M u l l e r & F i n d l a y , 1988). R e f l e x i v e o r i e n t i n g w a s f o u n d to be h i g h l y resistant to i n f o r m a t i o n p r o v i d e d b y the cue; it c o u l d not be p r e v e n t e d g i v e n the p r o p e r t r i g g e r i n g s t i m u l u s . A t the same time, v o l u n t a r y attention w a s f o u n d to be susceptible to the effects of a s e c o n d a r y task as w e l l as to the a u t o m a t i c effects p r o d u c e d b y the sensory p r o p e r t i e s of the cue (e.g., M u l l e r & Rabbitt, 1989). T h i s difference b e t w e e n  4 reflexive a n d v o l i t i o n a l attention has been r e i n f o r c e d b y a w e a l t h of n e u r o i m a g i n g studies r e p o r t i n g that reflexive a n d v o l i t i o n a l o r i e n t i n g , as d e f i n e d b y the classic b e h a v i o r a l p a r a d i g m s , engage distinct n e u r a l circuits (e.g., P o s n e r & Petersen, 1990; Posner, 1992; C o r b e t t a , M i e z i n , S h u l m a n & Petersen, 1993; H o p f i n g e r , B u o n o c o r e & M a n g u n , 2000; C o r b e t t a & S h u l m a n , 2002). C o n v e r g i n g e v i d e n c e indicates that p o s t e r i o r p a r i e t a l l o b e a n d f r o n t a l cortex (more s p e c i f i c a l l y f r o n t a l eye f i e l d region) are i n v o l v e d i n c o n t r o l l i n g the d i r e c t i o n of covert v o l i t i o n a l attention as w e l l as the m a i n t e n a n c e of a n expectancy set. In contrast, the circuit that i n v o l v e s v e n t r a l frontal cortex a n d t e m p o r o p a r i e t a l j u n c t i o n s h o w s s u s t a i n e d a c t i v a t i o n , as m e a s u r e d b y f M R I , for detection of a b r u p t s t i m u l i . Because of the d i f f e r i n g m a t u r a t i o n a l rates of frontal a n d parietal cortices (e.g., J o h n s o n , 1997), m a r k e d d e v e l o p m e n t a l differences of reflexive a n d v o l i t i o n a l attention h a v e b e e n o b s e r v e d s u c h that f u l l y - f u n c t i o n i n g reflexive o r i e n t i n g is present s h o r t l y after b i r t h (Johnson, P o s n e r & Rothbart, 1991) w h i l e v o l i t i o n a l o r i e n t i n g reaches a d u l t - l i k e f u n c t i o n i n g m u c h later, p o s s i b l y at a r o u n d 8 years of age (e.g., B r o d e u r & E n n s , 1997). T h e k e y theoretical a s s u m p t i o n u n d e r l y i n g classic b e h a v i o r a l p a r a d i g m s of spatial attention is that central a r r o w cues e n g a g e d v o l i t i o n a l o r i e n t i n g m e c h a n i s m o n l y because they p r e d i c t s p a t i a l l y w h e r e the target w i l l a p p e a r ( M u l l e r & Rabbitt, 1989; R a f a l et a l , 1989; Jonides, 1981). In other w o r d s , w i t h o u t p r e d i c t i v e i n f o r m a t i o n about the target, a r r o w s w e r e r e g a r d e d as ineffective i n e l i c i t i n g a n y o r i e n t i n g response, a n d c o u l d not, b y v i r t u e of the s t i m u l u s characteristics, trigger a shift i n attention. T h i s v i e w stems l a r g e l y f r o m a classic s t u d y b y Jonides (1981, E x p e r i m e n t 2) that r e q u i r e d subjects to search a b r i e f l y presented array of letters for the target letter (L or R). Before the array a p p e a r e d , a central a r r o w cue, r a n d o m l y p o i n t i n g to one of the target locations, w a s flashed m o m e n t a r i l y at fixation. Results i n d i c a t e d that if subjects w e r e t o l d to ignore the a r r o w , o r i e n t i n g to the c u e d l o c a t i o n w a s absent c o m p a r e d to the c o n d i t i o n w h e r e  5 a r r o w h e a d w a s flashed at a p e r i p h e r a l location, s u g g e s t i n g that a n o n p r e d i c t i v e central a r r o w cue does not trigger reflexive attention. Several recent studies, h o w e v e r , indicate that this acceptance of a n u l l result w a s m i s t a k e n . Ristic, F r i e s e n , a n d K i n g s t o n e (2002) a s k e d p a r t i c i p a n t s to detect targets a p p e a r i n g to the left or r i g h t of a central a r r o w cue. I m p o r t a n t l y , the a r r o w w a s u n i n f o r m a t i v e of the target l o c a t i o n s u c h that it w a s r a n d o m l y p o i n t i n g to either of the t w o possible target locations. C o n t r a r y to the t r a d i t i o n a l result, p a r t i c i p a n t s w e r e a l w a y s faster to detect targets a p p e a r i n g at the c u e d c o m p a r e d to u n c u e d locations e v e n t h o u g h they u n d e r s t o o d that a r r o w d i r e c t i o n h a d n o p r e d i c t i v e m e a n i n g . Ristic et al (2002) o b s e r v e d faster R T s for c u e d targets at a range of cue-target intervals (195,600, a n d 1000 ms), d e m o n s t r a t i n g that u n i n f o r m a t i v e central a r r o w cues t r i g g e r e d a reflexive shift i n spatial attention. Interestingly, a n d c o n t r a r y to the t r a d i t i o n a l f r a m e w o r k , the attentional o r i e n t i n g i n d e x w a s m a r k e d b y a p r o l o n g e d facilitation for c u e d targets w i t h o u t b e i n g a c c o m p a n i e d b y i n h i b i t i o n at l o n g e r S O A intervals. It is i m p o r t a n t to note that this is not a n isolated instance r e p o r t i n g reflexive o r i e n t i n g i n response to centrally presented d i r e c t i o n a l u n i n f o r m a t i v e cues. S i m i l a r f i n d i n g s u s i n g central a r r o w s t i m u l i w e r e o b t a i n e d i n t w o other studies ( H o m m e l , Pratt, C o l z a t o & G o d j i n , 2001; T i p p l e s , 2002) as w e l l as i n other i n v e s t i g a t i o n s e m p l o y i n g other central d i r e c t i o n a l cues s u c h as eye gaze d i r e c t i o n of b o t h schematic faces (e.g., F r i e s e n a n d K i n g s t o n e , 1998) a n d images of real faces (e.g., D r i v e r et al, 1999; L a n g t o n & Bruce, 1999), h e a d o r i e n t a t i o n ( D r i v e r et al, 1999; L a n g t o n , 2000), a n d finger p o i n t i n g ( L a n g t o n & Bruce, 2000). T a k e n together, these recent results d e m o n s t r a t e that a range of n o n p r e d i c t i v e b u t d i r e c t i o n a l attention cues presented at central fixation, i n c l u d i n g a r r o w s , r e l i a b l y trigger a reflexive shift of spatial attention, w i t h the effect m a r k e d l y different effect f r o m the t r a d i t i o n a l reflexive effect, i.e., reflexive o r i e n t i n g i n is l o n g l i v e d a n d it is not a c c o m p a n i e d b y I O R .  6 Since the i n t r o d u c t i o n of the c u i n g p a r a d i g m i n e a r l y 1980s, the p o s s i b i l i t y of a central attentional cue t r i g g e r i n g reflexive attention w a s a b a n d o n e d , a n d , as a consequence n e v e r s e r i o u s l y entertained, a p r e m i s e that w a s l a r g e l y b a s e d o n f i n d i n g s r e p o r t e d b y Jonides i n 1981 (see K i n g s t o n e , S m i l e k , Ristic, F r i e s e n & E a s t w o o d , i n press for a r e v i e w ) . T h e recent studies, h o w e v e r , s h o w i n g that s p a t i a l l y n o n p r e d i c t i v e b u t d i r e c t i o n a l s t i m u l i p r o d u c e shifts i n reflexive attention, raise the p o s s i b i l i t y that reflexive attention m a y h a v e been c o n t r i b u t i n g to the effects o b s e r v e d i n the past w i t h s p a t i a l l y p r e d i c t i v e d i r e c t i o n a l s t i m u l i . I n l i g h t of this p o s s i b i l i t y , the m o s t i m p o r t a n t q u e s t i o n n o w becomes w h e t h e r the classic b e h a v i o r a l p a r a d i g m s u t i l i z i n g spatially i n f o r m a t i v e a r r o w s t i m u l i w e r e e s t i m a t i n g the c o n t r i b u t i o n of v o l i t i o n a l attention alone, as o r i g i n a l l y t h o u g h t (because the a r r o w is predictive), reflexive attention (because a r r o w is directional), o r p e r h a p s s o m e u n i q u e c o m b i n a t i o n of r e f l e x i v e a n d v o l i t i o n a l responses that result f r o m a n interaction generated b y cue d i r e c t i o n a l i t y a n d its i n f o r m a t i o n . T h i s test represents a c r u c i a l e x a m i n a t i o n of the v a l i d i t y of b o t h the classic e x p e r i m e n t a l p a r a d i g m a n d the a c c u m u l a t e d results that w e r e , o v e r the past years, generated b y it. I n t w o experiments r e p o r t e d here w e investigated this f u n d a m e n t a l question w h e r e b y o r i e n t i n g responses for s p a t i a l l y p r e d i c t i v e a n d n o n p r e d i c t i v e d i r e c t i o n a l (arrow) a n d n o n d i r e c t i o n a l (digit) attentional cues w e r e dissociated. If the classic line of t h o u g h t is correct, t h a n w e s h o u l d observe little or n o difference b e t w e e n the v o l i t i o n a l o r i e n t i n g effects generated i n response to s p a t i a l l y p r e d i c t i v e d i r e c t i o n a l cues c o m p a r e d to s p a t i a l l y p r e d i c t i v e n o n d i r e c t i o n a l central cues. If, i n contrast, the t r a d i t i o n a l p a r a d i g m w a s not m e a s u r i n g v o l i t i o n a l o r i e n t i n g alone, one w o u l d p r e d i c t m a r k e d differences i n the attentional effect p r o d u c e d b y a r r o w a n d d i g i t cues.  7 Experiment 1 E x p e r i m e n t 1 w a s d e s i g n e d to measure attentional o r i e n t i n g i n response to s p a t i a l l y p r e d i c t i v e a n d n o n p r e d i c t i v e central cues. S p a t i a l p r e d i c t i v e n e s s w a s v a r i e d across t w o different cues types: d i r e c t i o n a l a r r o w cues a n d n o n d i r e c t i o n a l d i g i t cues. A s n o t e d , recent studies demonstrate that central a r r o w cues trigger reflexive shift of attention e v e n w h e n a r r o w d i r e c t i o n does not r e l i a b l y p r e d i c t the target l o c a t i o n (e.g., Ristic et a l , 2002). T h e a i m here w a s to e m p l o y a central cue that w o u l d not h a v e inherent d i r e c t i o n a l i t y a n d thus w o u l d n o t engage reflexive attention. H o w e v e r , w h e n this cue w a s g i v e n p r e d i c t i v e value, it w o u l d p r o v i d e a p u r e m e a s u r e of v o l i t i o n a l o r i e n t i n g . T h e c r i t i c a l c o m p a r i s o n here is w h e t h e r v o l i t i o n a l o r i e n t i n g t r i g g e r e d b y s u c h n o n d i r e c t i o n a l cues matches the v o l i t i o n a l o r i e n t i n g effect p r o d u c e d b y the classic s p a t i a l l y p r e d i c t i v e a r r o w cues. Method Participants F o r t y eight (48) u n d e r g r a d u a t e students p a r t i c i p a t e d i n the e x p e r i m e n t i n exchange for m o n e t a r y c o m p e n s a t i o n (24 p a r t i c i p a t e d i n each of the t w o cue type c o n d i t i o n s ) . A l l observers w e r e n a i v e to the p u r p o s e of the e x p e r i m e n t a n d r e p o r t e d n o r m a l or corrected-to-normal v i s i o n . 1  Apparatus and Stimuli S t i m u l u s presentation a n d t i m i n g w a s c o n t r o l l e d b y V S c o p e 1.2.7 software (Rensink, 1995) r u n n i n g o n the 6100/66 P o w e r M a c i n t o s h c o m p u t e r . S t i m u l i w e r e p r e s e n t e d o n a 15-inch A p p l e color m o n i t o r set to b l a c k a n d w h i t e , o p e r a t i n g at 6 5 H z screen refresh rate. Seven participants were excluded from the initial sample comprised of 55 participants. Because the task was a simple detection task, we adopted a stringent criterion based on which all observers who made more than 5% errors across both cue conditions were excluded from the analysis. 1  8 T h e s t i m u l i a n d s a m p l e t i m i n g sequence are i l l u s t r a t e d i n F i g u r e 1. A l l s t i m u l i w e r e b l a c k line d r a w i n g s presented o n w h i t e b a c k g r o u n d . A r r o w cues w e r e created b y c o m b i n i n g a straight line (2.1° long) w i t h a n a r r o w h e a d a n d a n a r r o w t a i l ( w i t h each 45degree o r i e n t e d l i n e m e a s u r i n g 1° i n length) attached to b o t h ends of the line (e.g., <-<). The w h o l e a r r o w m e a s u r e d 3. 3° of v i s u a l angle i n l e n g t h as m e a s u r e d f r o m the tip of the a r r o w h e a d to the e n d of the a r r o w t a i l . D i g i t cues (3, 6, a n d 9) w e r e 3. 3° i n height a n d 2° i n w i t h the exception of n u m b e r 1 w h i c h w a s created u s i n g a capital letter I (3.2° l o n g a n d 0.5° w i d e ) . T h e n u m b e r cues w e r e created u s i n g the G e n e v a font of 100 p o i n t s i n size. B o t h a r r o w a n d n u m b e r cues w e r e p o s i t i o n e d s u c h that the center of the a r r o w a n d the center of the d i g i t w a s a l w a y s a l i g n e d w i t h the center of the screen. A t the start of each trial, a central f i x a t i o n p o i n t s u b t e n d i n g 1°, c o m p r i s e d of t w o p e r p e n d i c u l a r intersecting lines (each 1° i n length), a p p e a r e d at the center of the screen. T h e target w a s a l w a y s a black asterisk ( m e a s u r i n g .9°) that a p p e a r e d w i t h eccentricity of 6.5° as m e a s u r e d f r o m the center of the cue to the center of the target. T h e center of the target w a s a l i g n e d w i t h the center of b o t h a r r o w a n d n u m b e r cues a l o n g the h o r i z o n t a l a n d v e r t i c a l axes.  Directional Cue  Nondirectional Cue  675 ms  E  Cue Onset  100, 300, 600, 900 SOA  Target Onset until response or 2700ms  Figure 1 illustrates the stimuli and timing sequences for directional (arrow) and nondirectional (digit) cue conditions. Identical stimuli and presentation sequence were used i n both Experiment 1 and Experiment 2. A straight line or a fixation point appeared on the screen for 675 ms. Then, an arrow pointing left, right, up or down, or a central number cue (1, 3, 6, 9) appeared on the screen. The target appeared either to the left, right, up or down after 100, 300, 600 or 900 ms. Both the cue and the target remained on the screen until response was made or for 2700ms, whichever came first. Intertrial interval was 525 ms. Note that the stimuli are not drawn to scale.  Design C u e t y p e ( a r r o w or n u m b e r ) w a s v a r i e d b e t w e e n subjects so that each g r o u p r e s p o n d e d to a single central cue (either a r r o w or n u m b e r ) . B o t h central cues w e r e v a r i e d as either s p a t i a l l y p r e d i c t i v e ( p r o b a b i l i t y of the target o c c u r r i n g at the c u e d l o c a t i o n =. 8) or s p a t i a l l y n o n p r e d i c t i v e ( p r o b a b i l i t y of the target o c c u r r i n g at the c u e d l o c a t i o n p=. 25) of the target location. C u e predictiveness w a s v a r i e d w i t h i n subjects s u c h that each p a r t i c i p a n t r e s p o n d e d to b o t h predictiveness c o n d i t i o n s . C u e p r e d i c t i v e n e s s o r d e r w a s c o u n t e r b a l a n c e d across p a r t i c i p a n t s s u c h that half the  10 p a r t i c i p a n t s i n each g r o u p (N=12) received s p a t i a l l y p r e d i c t i v e cues first a n d the other half (N=12) r e c e i v e d s p a t i a l l y n o n p r e d i c t i v e cues first. A r r o w C u e s . O n e v e r y trial, a central cue c o u l d be d i r e c t e d to the left, right, u p , or d o w n c o n s t i t u t i n g f o u r p o s s i b l e target locations (left, right, u p , d o w n ) . I n the n o n p r e d i c t i v e c o n d i t i o n , the target a p p e a r e d w i t h e q u a l p r o b a b i l i t y at a l l four locations (p=. 25). A l l possible cue directions a n d target locations w e r e d i s t r i b u t e d e q u a l l y t h r o u g h o u t the experiment. In the p r e d i c t i v e c o n d i t i o n h o w e v e r , the target a p p e a r e d at the l o c a t i o n to w h e r e the a r r o w w a s p o i n t i n g i n 80% of a l l trials. I n r e m a i n i n g 20% of trials targets a p p e a r e d e q u a l l y often a m o n g three r e m a i n i n g locations (6.67% for each of the three locations). Trials i n w h i c h the target a p p e a r e d at the l o c a t i o n to w h e r e the a r r o w w a s p o i n t i n g are labeled as c u e d target trials a n d the trials i n w h i c h the target a p p e a r e d at a n y of three other possible locations are l a b e l e d as u n c u e d target trials. N u m b e r C u e s . F o r the n u m b e r cues one of the four p o s s i b l e digits ( 1 , 3 , 6 , 9 ) a p p e a r e d at the center of the screen at the b e g i n n i n g of each trial. W h e n n u m b e r cues w e r e u n i n f o r m a t i v e of the target location, the targets a p p e a r e d w i t h e q u a l p r o b a b i l i t y (p=. 25) at a l l f o u r p o s s i b l e locations (left, right, u p , d o w n ) regardless of w h i c h central d i g i t a p p e a r e d o n the screen. H o w e v e r , w h e n the n u m b e r cue w a s p r e d i c t i v e of the target location, the e x p e r i m e n t w a s set u p so that n u m b e r 3 p r e d i c t e d the target o c c u r r i n g o n the right, n u m b e r 9 the target o c c u r r i n g o n the left, n u m b e r 1 the target o c c u r r i n g u p , a n d n u m b e r 6 the target o c c u r r i n g d o w n . A l l f o u r cues w e r e p r e s e n t e d e q u a l l y often t h r o u g h o u t the experiment. M i r r o r i n g the setup e m p l o y e d for a r r o w cues, s p a t i a l l y p r e d i c t i v e d i g i t cues correctly i n d i c a t e d target l o c a t i o n o n 80% of a l l trials. I n the r e m a i n i n g 20% of the trials the target a p p e a r e d r a n d o m l y at one of the three r e m a i n i n g locations (6.67% p e r location). F o r a l l cue types (arrows a n d n u m b e r s ) a n d cue p r e d i c t i v e n e s s ( n o n p r e d i c t i v e or p r e d i c t i v e ) c o n d i t i o n s , four cue-target onset delays (100,300, 600 a n d 900 ms) w e r e •  11 v a r i e d e q u a l l y a m o n g a l l p o s s i b l e trials. In a l l c o n d i t i o n s p a r t i c i p a n t s w e r e a s k e d to p e r f o r m a s p e e d e d target detection response b y p r e s s i n g the spacebar k e y o n the k e y b o a r d w i t h the i n d e x finger of their p r e f e r r e d h a n d . A d d i t i o n a l l y , i n a p p r o x i m a t e l y 6% of a l l trials w i t h i n each of the four c o n d i t i o n s the target w a s n o t presented o n the screen. These catch trials w e r e d i s p e r s e d r a n d o m l y across a l l p o s s i b l e cue directions a n d w e r e i n c l u d e d to ensure that participants r e s p o n d e d to target onset a n d not its a n t i c i p a t e d appearance. Procedure T h e start of e v e r y trial w a s s i g n a l e d b y a 675ms p r e s e n t a t i o n of a f i x a t i o n cross i n the center of the c o m p u t e r screen. T h e n , a central cue (either a r r o w p o i n t i n g left, right, u p , or d o w n , or one of the four n u m b e r cues) a p p e a r e d o n the screen. T h e target d e m a n d i n g a s i m p l e detection response a p p e a r e d at one of the f o u r target locations after 100,300,600, or 900 m s . T h e trial t e r m i n a t e d o n response or after 2700ms, w h i c h e v e r came first. The intertrial i n t e r v a l w a s set at 525 m s . R e a c t i o n T i m e (RT) w a s m e a s u r e d f r o m target onset a n d it w a s b a s e d o n e x e c u t i o n of the k e y b o a r d responses. E a c h cue t y p e x cue predictiveness c o n d i t i o n (arrow n o n p r e d i c t i v e ; a r r o w predictive; n u m b e r n o n p r e d i c t i v e ; a n d n u m b e r p r e d i c t i v e ) w a s c o m p r i s e d of 480 e x p e r i m e n t a l trials d i s t r i b u t e d o v e r 8 b l o c k s of 60 trials. T h u s , each p a r t i c i p a n t c o m p l e t e d a total of 960 trials, 480 i n response to each cue predictiveness c o n d i t i o n . P a r t i c i p a n t s w e r e seated i n a d i m l y lit r o o m centered w i t h respect to the c o m p u t e r screen a n d the k e y b o a r d at a p p r o x i m a t e distance of 57 c m . Before the c o m m e n c e m e n t of the experiment, observes w e r e s h o w n a p i c t u r e of a t y p i c a l e x p e r i m e n t a l trial. T h e y w e r e i n f o r m e d about the t y p e of the central cue, its possible directions (or values), a n d possible target locations. D e p e n d i n g o n the cue p r e d i c t i v e n e s s c o n d i t i o n , observers w e r e i n f o r m e d that the cues w e r e either n o n p r e d i c t i v e or p r e d i c t i v e of the target locations. T h e y w e r e e x p l i c i t l y t o l d , a n d  12 u n d e r s t o o d , the probabilities of the target occurrence for either a r r o w or n u m b e r central cues. T e n practice trials w e r e r u n before the first testing b l o c k , a n d the experimenter offered to a n s w e r a n y questions after the practice r u n w a s c o m p l e t e d . Participants w e r e i n s t r u c t e d h o w to initiate testing b l o c k s a n d w e r e i n f o r m e d about the d u r a t i o n of the e x p e r i m e n t a n d their total time c o m m i t m e n t . A l l p a r t i c i p a n t s w e r e a s k e d to r e s p o n d as fast a n d as accurately as they c o u l d a n d to m a i n t a i n central f i x a t i o n t h r o u g h o u t the experiment. Results Incorrect k e y presses, anticipations (RT<100 ms), t i m e d - o u t responses (RT>1000ms), a n d false a l a r m s ( r e s p o n d i n g w i t h a k e y p r e s s w h e n the target w a s not present) w e r e classified as errors a n d w e r e e x c l u d e d f r o m the analysis. F o r the a r r o w central cues, anticipations a c c o u n t e d for 0.47% of a l l trials w h i l e t i m e d - o u t responses a c c o u n t e d for 0.26% of a l l target-present trials across b o t h p r e d i c t i v e n e s s c o n d i t i o n s . O v e r a l l false a l a r m rate w a s 0.62%. F o r d i g i t central cues, anticipations a c c o u n t e d for 0.53%, t i m e d o u t trials for 0.26%, a n d k e y press errors for 0.004% of a l l target present trials. False a l a r m rate w a s 1.02%. A s each t y p e of error a c c o u n t e d for less than 2% of a l l trials, errors w e r e not a n a l y z e d further. M e a n error rates for each of the S O A b y v a l i d i t y c o n d i t i o n are p r e s e n t e d i n Table 1.  13  Arrow Condition  nonpredictive  Number predictive  nonpredictive  predictive  SD  %E  .003 344.8 38.9 .002 355.2  50.6  .001  57.3  .004 345.9 42.8 .002 360  51  .006  316.8  48.6  .014 326  42.2  .013  .018  358.8  48  .017 324.9 38.7 .02  340.5  46.3  .011  43.9  .004  304.8  42.1  .007 307.7 43.1 .006  300.9  39  .009  321.5  47.1  .006  350.6  52.7  .004 310.1 36.4 .006  330.5  49.2  .011  Cued  321.3  50.1  .007  317.0  44.3  .006 322.9 45  .004  313.4  44.2  .006  Uncued  330.7  47.6  .005  354.9  46.3  .011 318.6 40  .006  340.1  47  .004  M  SD  0  349  51.0  50.5  .002  369  324.1  51.7  .009  334.5  52.4  Cued  305.1  Uncued  M  SD  Cued  342.7  52.6  Uncued  348.7  Cued Uncued  %E  %E  M  SD  %E  M  100 ms SOA  300 ms SOA 41.9 .017 323.4  600 ms SOA  900 ms SOA  Tablel. Mean response times (RTs), standard deviations, and error rates for Experiment 1. T h e correct R T m e a n s are i l l u s t r a t e d i n F i g u r e s l a a n d l b for the a r r o w a n d digit central cues as a f u n c t i o n of S O A a n d cue v a l i d i t y . A r r o w cues w e r e effective i n t r i g g e r i n g o r i e n t i n g b o t h as n o n p r e d i c t i v e a n d p r e d i c t i v e of a target p o s i t i o n . R e p l i c a t i n g p r e v i o u s results (e.g., Jonides, 1981; Ristic et a l , 2002), o n average, p a r t i c i p a n t s r e s p o n d e d faster to targets at c u e d c o m p a r e d to n o n c u e d locations. N u m b e r cues, o n the other h a n d , w e r e effective o n l y w h e n they p r e d i c t e d target locations.  14 A l t h o u g h b o t h types of p r e d i c t i v e cues (arrow a n d digit) p r o d u c e d significant o r i e n t i n g effects, the c u i n g effect ( u n c u e d R T m i n u s c u e d R T ) w a s m u c h larger for the p r e d i c t i v e a r r o w cue. F i g u r e 2c illustrates the c u i n g effects for a l l types of cues. A: Directional Cue 375  .Q;  nonpredictive arrow  v.V  358  E i - 341 co  \ \  t; 324  ro CU  cC  c ro 307 <u Z 290  •  V  1  1  1  predictive arrow  Q  1  100 300 600 900 SOA  I  I  I  legend uncued cued I  100 300 600 900 SOA  B: Nondirectional Cue 375  .—'  nonpredictive number  358  CU  E i - 341 co  '•6 324 cro u cC  c 307 to  cu T.  290  •  0  2,  \  v V  N  \  \  •  . V 1  —I  1  1  100 300 600 900 SOA  predictive number  legend uncued cued  I I 300I 600 ! 100 900  SOA  C: Cuing Effects 50  legend •o  cu D  predictive arrow  u  •a v  predictive number  c  nonpredictive arrow  I  U  3  nonpredictive number  100  300  600  900  SOA  Figure 2 shows results from Experiment 1. Figure 2a shows mean response times (RTs) plotted as a function of S O A and validity for nonpredictive and predictive directional arrow cues. Figure 2b shows mean RTs for nonpredictive and predictive central digit cues. Figure 2c plots the difference between uncued and cued RTs from all four conditions presented in Figures 2a and 2b.  15 These observations w e r e first c o n f i r m e d b y 2 separate w i thin-subjects A N O V A s w i t h cue predictiveness, S O A , a n d v a l i d i t y , c o n d u c t e d o n each of the cue t y p e separately . S i g n i f i c a n t m a i n effects of b o t h S O A a n d v a l i d i t y w e r e o b s e r v e d for b o t h 2  a r r o w [F (3, 69)= 42.6, p < .0001; F (1, 23)= 101.47, p < .0001] a n d n u m b e r center cues [F (3, 69)= 39.42, p < .0001; F (1, 23)= 16.43, p < .0001 respectively] i n d i c a t i n g a p r e p a r a t o r y set for i n c r e a s i n g S O A intervals, a n d o v e r a l l faster R T s for c u e d c o m p a r e d to u n c u e d targets, respectively. T h e cue predictiveness x v a l i d i t y [all Fs> 4.0, ps< .05] interaction w a s significant i n b o t h analyses, as w e l l as a t h r e e - w a y i n t e r a c t i o n b e t w e e n cue predictiveness, S O A , a n d v a l i d i t y [arrow: F (3, 69)= 2.82, p < . 05; digit: F (3, 69)= 4.21, p< .01]. T h u s , the v a l i d i t y effect differed w i t h respect to S O A a n d t w o predictiveness c o n d i t i o n s for each cue type as i l l u s t r a t e d i n F i g u r e 2c. N e x t , i n o r d e r to e x a m i n e p o t e n t i a l differences b e t w e e n the t w o cues, cue type (arrow, n u m b e r ) w a s i n c l u d e d as a b e t w e e n -subject v a r i a b l e i n a separate f o u r - w a y b e t w e e n - w i t h i n A N O V A . Significant m a i n effects of v a l i d i t y [F (1, 46)= 99.29, p < . 0001], S O A [F (3,138)= 80.19, p < . 0001], a n d cue predictiveness [F (1,46)= 6.83, p < . 05] w e r e o b s e r v e d . T h e highest o r d e r interaction that reached significance w a s a t h r e e - w a y interaction b e t w e e n cue predictiveness, S O A , a n d v a l i d i t y [F (3,138)= 6.4, p < . 001] i n d i c a t i n g that o r i e n t i n g effect v a r i e d differently across S O A for s p a t i a l l y p r e d i c t i v e a n d s p a t i a l l y n o n p r e d i c t i v e cues. T w o t w o - w a y interactions b e t w e e n cue predictiveness a n d Although the order of cue predictiveness presentation was counterbalanced across subjects for both cue types, we included it as a between-subject variable i n a preliminary analyses conducted on each of the cue type separately. N o order effects interacting w i t h validity were observed. For the arrow cues a four-way between (order)-within (cue predictiveness, SOA, and validity) omnibus A N O V A conducted on mean RT with returned a significant interaction between cue predictiveness and order [F (1, 22)= 12.46, p<. 01] reflecting the issue that both predictive and nonpredictive cues were overall responded to faster when received second with the effect being bigger for the predictive cues. N o other effects or interactions involving presentation order were significant [all Fs< 2.6, all ps>.06]. The same analysis was performed on digit central cues. The only significant effect involving order was again an interaction with cue predictiveness [F (1, 22)= 7.69, p< .05] reflecting that again cue predictiveness condition received second was overall responded to faster. Importantly, an interaction involving validity and order was not present [all Fs<l]. 2  16 v a l i d i t y [F (1,46)= 110.05, p < . 0001] a n d S O A a n d v a l i d i t y [F (3,138)= 11.8, p < . 0001] d e m o n s t r a t i n g the s i m i l a r t r e n d w e r e also significant. H o w e v e r , the interaction b e t w e e n cue predictiveness, v a l i d i t y , a n d cue t y p e w a s n o n s i g n i f i c a n t [p>. 2] i n d i c a t i n g that, o v e r a l l , the p a t t e r n of o r i e n t i n g i n response to n o n i n f o r m a t i v e a n d i n f o r m a t i v e cues w a s not statistically different b e t w e e n d i r e c t i o n a l a n d n o n d i r e c t i o n a l attentional cues. W h e n n o n d i r e c t i o n a l n u m b e r cues w e r e v a r i e d i n d e p e n d e n t l y of the target p o s i t i o n , n o differences i n R T s w e r e o b s e r v e d for c u e d c o m p a r e d to u n c u e d targets. In contrast, w h e n n u m b e r cues w e r e m a d e p r e d i c t i v e of the target location, a significant c u i n g effect at l o n g e r S O A intervals w a s o b s e r v e d , d e m o n s t r a t i n g a result consistent w i t h b e h a v i o r a l i n d e x of v o l i t i o n a l o r i e n t i n g (e.g., M u l l e r & Rabbitt, 1989). A recent s t u d y (Fisher, C a s t e l , D o d d & Pratt, 2003) r e p o r t e d that n u m e r i c a l l y l o w centrally p r e s e n t e d n u m b e r cues (1 a n d 2) trigger a n a u t o m a t i c shift of attention to targets a p p e a r i n g i n the left v i s u a l f i e l d w h e r e a s n u m e r i c a l l y h i g h n u m b e r s (8 a n d 9) i n d u c e a shift of spatial attention t o w a r d s the r i g h t v i s u a l f i e l d . T o e x a m i n e w h e t h e r this effect w a s o p e r a t i n g i n the present data, w e a n a l y z e d m e a n R T s i n response to s p a t i a l l y n o n p r e d i c t i v e d i g i t cues (1,3, 6,9) as a f u n c t i o n of S O A (100,300,600, a n d 900 ms) a n d target p o s i t i o n (left, right, u p , or d o w n ) . N o significant i n t e r a c t i o n i n v o l v i n g cue type a n d target p o s i t i o n w a s o b s e r v e d [F (9, 207) = 1.79, p > .05] i n d i c a t i n g that i n d e e d this spatial bias w a s n o t o p e r a t i n g i n o u r data a n d as s u c h d i d n o t i n f l u e n c e the m a g n i t u d e of v o l i t i o n a l o r i e n t i n g w h e n d i g i t cues w e r e m a n i p u l a t e d as s p a t i a l l y p r e d i c t i v e . O v e r a l l , the results f r o m E x p e r i m e n t 1 i n d i c a t e that w h e n v a r i e d as spatially p r e d i c t i v e of the target p o s i t i o n , b o t h a r r o w a n d n u m b e r cues p r o d u c e d significant c u i n g effects for targets a p p e a r i n g at the p r e d i c t e d locations. I n contrast to n u m b e r cues, o n l y d i r e c t i o n a l a r r o w triggered a reflexive shift of attention w h e n it w a s u n i n f o r m a t i v e of the target p o s i t i o n , a n d w h e n i t w a s m a d e s p a t i a l l y p r e d i c t i v e the size of o r i e n t i n g effect s u r p a s s e d that of s y m b o l i c i n f o r m a t i v e d i g i t cues.  17 Discussion W h e n cue d i r e c t i o n a l i t y a n d cue predictiveness are e x p e r i m e n t a l l y dissociated, m a r k e d differences i n m a g n i t u d e of v o l i t i o n a l o r i e n t i n g i n response to d i r e c t i o n a l a n d n o n d i r e c t i o n a l attentional cues emerge: P r e d i c t i v e a r r o w cues p r o d u c e d larger o r i e n t i n g effects t h a n p r e d i c t i v e n o n d i r e c t i o n a l d i g i t cues. H o w e v e r , w h e n o r i e n t i n g i n response to the t w o cues w a s c o m p a r e d i n a between-subject a n a l y s i s n o significant interaction b e t w e e n cue type, cue v a l i d i t y , a n d predictiveness w a s o b s e r v e d . T h i s result raises t w o possible explanations. First, it is i n d e e d possible that o r i e n t i n g i n response to n o n d i r e c t i o n a l a n d d i r e c t i o n a l p r e d i c t i v e cues does not differ, a f i n d i n g that w o u l d v a l i d a t e t r a d i t i o n a l c u i n g studies. H o w e v e r , this does not agree w i t h o u r observations as i l l u s t r a t e d i n F i g u r e 2c. A n alternative e x p l a n a t i o n is that the cue t y p e w a s i n c l u d e d as a between-subject factor a n d the present e x p e r i m e n t l a c k e d the necessary p o w e r to detect a significant difference b e t w e e n the m a g n i t u d e s of o r i e n t i n g to p r e d i c t i v e d i r e c t i o n a l a n d p r e d i c t i v e n o n d i r e c t i o n a l cues. E x p e r i m e n t 2 w a s c o n d u c t e d i n order to address this alternative. Experiment 2 T h e results f r o m E x p e r i m e n t 1 d e m o n s t r a t e d that the m a g n i t u d e of o r i e n t i n g effect t r i g g e r e d b y p r e d i c t i v e a r r o w cues a l w a y s exceeded o r i e n t i n g effects elicited b y a n u n c o n t a m i n a t e d m e a s u r e of v o l i t i o n a l o r i e n t i n g p r o d u c e d b y s y m b o l i c d i g i t cues. H o w e v e r , this m a g n i t u d e difference w a s not reliable. A l t h o u g h the data f r o m E x p e r i m e n t 1 are c o n v i n c i n g , the fact r e m a i n s that the results d i d n o t s h o w statistical difference b e t w e e n the t w o cues w h e n tested i n a n o m n i b u s A N O V A . I n a d d i t i o n , e v e n if a reliable difference i n o r i e n t i n g m a g n i t u d e b e t w e e n the p r e d i c t i v e a r r o w a n d d i g i t cues h a d b e e n o b s e r v e d , the fact r e m a i n s that cue type w a s m a n i p u l a t e d b e t w e e n subjects. A s s u c h there is a real p o s s i b i l i t y that a n y p o t e n t i a l differences i n o r i e n t i n g m i g h t h a v e reflected g r o u p differences rather than differences i n attentional orienting.  18 T o address b o t h these issues, w e e x a m i n e d w h e t h e r reliable difference w o u l d be o b s e r v e d w h e n the effects are m e a s u r e d entirely w i t h i n the same g r o u p of participants. Method Participants T h e d a t a f r o m a d d i t i o n a l f o r t y eight (48) u n d e r g r a d u a t e students f r o m the U n i v e r s i t y of B r i t i s h C o l u m b i a w e r e i n c l u d e d i n the analysis. A l l p a r t i c i p a n t s w e r e b l i n d to the p u r p o s e of the e x p e r i m e n t a n d n o n e h a d p a r t i c i p a t e d i n a n y p r e v i o u s c o n d i t i o n s . T e s t i n g w a s d i v i d e d o v e r t w o sessions i n d u r a t i o n of less t h a n one h o u r each that w e r e c o n d u c t e d o n separate d a y s . Apparatus, Stimuli, Design, and Procedure E x p e r i m e n t a l parameters w e r e k e p t i d e n t i c a l to those o f E x p e r i m e n t 1 unless e x p l i c i t l y stated. A l l participants c o m p l e t e d a l l four cue t y p e x cue predictiveness c o n d i t i o n s . C u e t y p e (arrow or n u m b e r ) w a s c o u n t e r b a l a n c e d w i t h i n subjects across sessions s u c h that h a l f the p a r t i c i p a n t s r e c e i v e d (N=24) a r r o w cues first a n d the other half r e c e i v e d n u m b e r cues first (N=24). O r d e r of cue p r e d i c t i v e n e s s (nonpredictive; p r e d i c t i v e ) p r e s e n t a t i o n w a s counterbalanced b o t h b e t w e e n a n d w i t h i n subjects s u c h that half of a l l observers (N=24) received p r e d i c t i v e cues f o l l o w e d b y n o n p r e d i c t i v e cues i n the first session a n d the other half (N=24) r e c e i v e d the o p p o s i t e o r d e r i n their first session. C o u n t e r b a l a n c i n g of cue type a n d cue p r e d i c t i v e n e s s w a s c o m p l e t e l y crossed s u c h that each g r o u p of 12 p a r t i c i p a n t s r e c e i v e d a distinct c o m b i n a t i o n of a r r o w a n d n u m b e r cues b e t w e e n sessions as w e l l as t w o cue p r e d i c t i v e n e s s orders w i t h i n sessions. C u e t y p e w a s k e p t constant w i t h i n a single session i n o r d e r to m a t c h e x p e r i m e n t a l m a n i p u l a t i o n w i t h that u s e d i n E x p e r i m e n t 1. E a c h p a r t i c i p a n t c o m p l e t e d a total of 1920 e x p e r i m e n t a l trials, 480 i n response to each cue t y p e x cue predictiveness c o n d i t i o n .  19 Results A s i n E x p e r i m e n t 1, anticipations (RT<100) t i m e d - o u t responses (RT>1000 m s ) , /  a n d false a l a r m s w e r e e x c l u d e d f r o m the analysis. E r r o r s o c c u r r e d o n less t h a n 1% of a l l target trials w h i l e false a l a r m s o c c u r r e d o n less t h a n 2.1% n o target trials i n each of the cue p r e d i c t i v e n e s s c o n d i t i o n s . E r r o r s w e r e n o t a n a l y z e d further. M e a n correct R T s for a l l cue p r e d i c t i v e n e s s c o n d i t i o n s are s h o w n i n Table 2 a n d i l l u s t r a t e d i n F i g u r e 3a for a r r o w cues a n d F i g u r e 3b for n u m b e r cues.  Number  Arrow Condition  nonpredictive  predictive  nonpredictive  predictive  M  SD  %E  57  .009  58.3  .005  .022 321.5  50.2  .025  49.3  .029 334.1  57.1  .033  308.6  44.9  .011 307.4  46.2  .014  .007  313.6  45.9  .009 322.1  45.2  .019  40.1  .007  316.2  46.3  .011 311.1  41  .013  48.3  .01  319.8  45.5  .011 325.6  39.3  .01  M  SD  %E  M  SD  %E  M  SD  %E  Cued  343.2  64.2  .007  342.3  56.7  .004  347.4  63.5  .007 347  Uncued  352.1  61.8  .009  366.7  72  .006  343.9  57.1  .01  323.2  59.6  .027  311.5  49.7  .027  324.7  55.6  332  57.8  .027  354.6  55.3  .029  324  Cued  306.8  46  .008  299.3  41.5  .011  Uncued  318.5  48  .01  337.7  44  313  48.5  .004  308.2  325.1  44.2  .012  339.4  100 ms SOA  348  300 ms SOA Cued Uncued 600 ms SOA  900 ms SOA Cued Uncued  Table 2. Mean response times (RTs), standard deviations, and error rates for Experiment 2.  20 A: Directional Cue 375  £ cu  3  j! c o  341  5  nonpredictive arrow  predictive arrow  8  legend  " 'g  324  |  307  uncued cued  290  100 300 600 9 0 0  100 300 600 900  SOA  SOA  B: Nondirectional Cue 375  358 .—'  cu E 341 ic o tj 324  \  ID CU  a: c  307  ID CU  predictive number  nonpredictive number  290  yv-°  V •  •  •  I  •  Vi  i  legend uncued cued  i  100 300 600 900  100 300 600 900  SOA  SOA  C: Cuing Effects 50  legend •a cu  u  predictive arrow  I T 3 CU 3 <J C  -®-  predictive number nonpredictive arrow  3  nonpredictive number  100  300  600  900  Figure 3 shows results rlrjirh Experiment 2. Figure 3a shows mean response times (RTs) plotted as a function of S O A and validity for nonpredictive and predictive directional arrow cues. Figure 3b shows mean RTs for nonpredictive and predictive central digit cues. Figure 3c plots the difference between uncued and cued RTs from all four conditions presented in Figures 3a and 3b. A s i l l u s t r a t e d i n F i g u r e s 3a a n d 3b the results m i r r o r e d those o b t a i n e d i n E x p e r i m e n t 1. These observations w e r e e x a m i n e d u s i n g a f o u r - w a y within-subjects A N O V A w i t h cue type (arrow, n u m b e r ) , cue p r e d i c t i v e n e s s ( n o n p r e d i c t i v e , predictive),  21 S O A (100,300, 600, a n d 900 ms), a n d v a l i d i t y (cued, u n c u e d ) i n c l u d e d as factors . The 3  results i n d i c a t e d that, o n average, observers w e r e faster to detect targets a p p e a r i n g after l o n g e r cue-target d e l a y s [F (3,141)= 59.4, p< .0001] as w e l l as that o v e r a l l c u e d targets w e r e detected faster t h a n u n c u e d targets [F (1,47)= 167.78, p < .0001]. T w o t w o - w a y interactions b e t w e e n cue type a n d v a l i d i t y [F (1,47) = 89.67, p < .0001] a n d cue predictiveness a n d v a l i d i t y [F (1, 47)= 97.08, p < . 0001] w e r e h i g h l y significant. A threew a y i n t e r a c t i o n b e t w e e n cue predictiveness, S O A , a n d v a l i d i t y w a s also significant [F (3,141)= 4.62, p < .01] reflecting that the c u i n g effect d i f f e r e d across S O A intervals b u t o n l y w h e n attentional cues w e r e m a d e s p a t i a l l y p r e d i c t i v e of the target. I m p o r t a n t l y , so w a s the t h r e e - w a y interaction b e t w e e n cue type, cue p r e d i c t i v e n e s s , a n d v a l i d i t y [F (1, 27)= 19.23, p < .0001] i n d i c a t i n g that s p a t i a l l y p r e d i c t i v e a r r o w cues p r o d u c e d s i g n i f i c a n t l y larger o r i e n t i n g effects than the p r e d i c t i v e n u m b e r cues. A s i n E x p e r i m e n t 1, i n o r d e r to v e r i f y that s p a t i a l l y n o n p r e d i c t i v e n u m b e r cues d i d not p r o d u c e a n y R T facilitation for a n y of the possible target p o s i t i o n s , the data f r o m u n i n f o r m a t i v e d i g i t c o n d i t i o n w e r e a n a l y z e d as a f u n c t i o n of S O A (100, 300, 600, a n d 900 ms), n u m b e r cue ( 1 , 3 , 6 , 9 ) , a n d target p o s i t i o n (left, right, u p , d o w n ) . The analysis i n d i c a t e d that, once again, cue type x target p o s i t i o n i n t e r a c t i o n w a s not  A s i n Experiment 1, order of cue presentation and cue predictiveness was included as a between-subject variable i n a preliminary analysis. First, to assess any possible effects of cue type presentation order, mean correct RT scores were subjected to a between (cue order: arrow, number) within (cue type, cue predictiveness, SOA, validity) A N O V A . The analysis returned no significant main effect of order [F<1] and significant interactions of cue order x cue type [F (1, 46)= 9.1, p<. 01] and cue type, cue validity, and cue order [F (1, 46)= 5.66, p<. 05] indicating that again both cue types were responded to faster when they were received second and that larger effect were observed for arrow cues regardless of whether they were received first or second. Next, to examine whether validity effects varied with order of cue predictiveness, it (nonpredictive, predictive) was entered as between-subject variable i n three-way between within A N O V A conducted on each of the two cues types separately including cue predictiveness, SOA, and validity as within-subject factors. Again, for both arrow and number cues, no main effects of cue predictiveness order were observed [both Fs<l]. The only significant interaction was observed in arrow condition between cue validity and order [F (1, 46)= 4.7, p<. 05] reflecting the fact that overall invalid trials were overall slower when predictive cues were received second. N o other interactions involving cue predictiveness and order of the presentation were significant [all Fs< 2.3, all ps>.085]. 3  22 significant [F (9, 423)= 1.4, p>. 15] demonstrating that any spatial bias induced by perception of numerically low and high numbers was not present i n our data. A s such, once again, we are confident that orienting effects observed i n response to spatially predictive digit cues accurately reflects the contribution of endogenous orienting alone. The results obtained i n Experiment 2 replicate those from Experiment 1. Spatially nonpredictive directional arrow cues were once again effective i n eliciting reflexive orienting while spatially nonpredictive digit cues were not. In addition both predictive arrow and number cues were effective i n eliciting volitional orienting. Spatially predictive arrow cues produced the largest orienting effects as illustrated i n Figure 3c. Discussion Experiment 2 manipulated cue type and cue directionality within the same group of observers. This manipulation allowed for a direct comparison of the magnitudes of the orienting effects generated by our four conditions (arrow nonpredictive; arrow predictive; number nonpredictive; number predictive). Thus, any differences between the orienting magnitudes were now independent of group differences because Experiment 2 was carried out within-subjects. The results mirrored those of Experiment 1, and indicated that a spatially predictive arrow cue, that was traditionally used i n a range of behavioral and neuroimaging studies of human volitional attention, triggers a shift of spatial attention that is reliably larger than the unconfounded measure of voluntary orienting measured by spatially informative symbolic digit cues. General Discussion A s outlined in the introduction, for over twenty years, the Posner paradigm has been widely used i n research investigations and predictive arrow cues have almost exclusively been used to elicit voluntary orienting responses. However, several recent findings (e.g., H o m m e l et al, 2001; Tipples, 2002; Ristic et al, 2002) demonstrate that central arrow cues, by a virtue of their inherent directionality, trigger a reflexive shift of  23 spatial attention. T w o e x p e r i m e n t s r e p o r t e d here e x a m i n e d the differences b e t w e e n the b e h a v i o r a l i n d e x of v o l i t i o n a l attention w h e n triggered b y s p a t i a l l y p r e d i c t i v e central d i r e c t i o n a l cues, s u c h as a r r o w s , a n d w h e n triggered b y p u r e l y s y m b o l i c n o n d i r e c t i o n a l i n f o r m a t i v e cues, that o n their o w n d o not p r o d u c e a shift i n attention automatically. In E x p e r i m e n t 1 w e dissociated o r i e n t i n g i n response to s p a t i a l l y p r e d i c t i v e directional a n d n o n d i r e c t i o n a l attentional cues. T h e data d e m o n s t r a t e d differences b e t w e e n the m a g n i t u d e s of v o l i t i o n a l o r i e n t i n g w h e n triggered b y the cue that, b y the v i r t u e of its s t i m u l u s characteristics, does not trigger a reflexive attentional shift a n d the o r i e n t i n g effect t r i g g e r e d b y the p r e d i c t i v e a r r o w cues. E x p e r i m e n t 2 r e p l i c a t e d this i n i t i a l result, a n d also d e m o n s t r a t e d that a difference i n m a g n i t u d e of attentional o r i e n t i n g i n response to d i r e c t i o n a l a r r o w a n d n o n d i r e c t i o n a l d i g i t cues w a s significant. T o address the i n i t i a l question p e r t a i n i n g to the v a l i d i t y of the classic p a r a d i g m s , the data f r o m the t w o e x p e r i m e n t s i n d i c a t e that the o r i e n t i n g i n response to s p a t i a l l y i n f o r m a t i v e a r r o w cues does not e q u a l either the reflexive or p u r e v o l u n t a r y effect. Instead, the large o r i e n t i n g effect elicited b y s p a t i a l l y p r e d i c t i v e a r r o w cues appears to be u n i q u e s u c h that the m a g n i t u d e of this o r i e n t i n g effect surpasses b o t h reflexive a n d v o l i t i o n a l effects. I n other w o r d s , its m a g n i t u d e c o u l d not be a c c o u n t e d for s i m p l y b y the a d d i t i o n of the reflexive a n d v o l u n t a r y o r i e n t i n g effects (see F i g u r e s 2c a n d 3c). A l t h o u g h this interpretation represents a p l a u s i b l e account for the data, it is still unclear w h e t h e r this large o r i e n t i n g effect arises as a result of a u n i q u e i n t e r a c t i o n b e t w e e n reflexive a n d v o l i t i o n a l o r i e n t i n g systems or w h e t h e r it represents a n isolated effect seen o n l y w i t h s p a t i a l l y i n f o r m a t i v e d i r e c t i o n a l cues, s u c h as a r r o w s . If the effect is l a r g e l y d u e to the interaction b e t w e e n the t w o o r i e n t i n g m e c h a n i s m s , one w o u l d p r e d i c t that the s i m i l a r results w o u l d emerge w h e n other attentional cues that trigger reflexive o r i e n t i n g w h e n s p a t i a l l y u n i n f o r m a t i v e a n d v o l u n t a r y o r i e n t i n g w h e n presented as i n f o r m a t i v e of the target are e m p l o y e d (e.g., a b r u p t p e r i p h e r a l onsets).  24 A d d i t i o n a l l y , since w e m e a s u r e d o r i e n t i n g response to t w o specific s t i m u l i o n l y , it is u n k n o w n w h e t h e r the s i m i l a r s u p e r a d d i t i v e b e h a v i o r a l result c o u l d be o b s e r v e d for other i n f o r m a t i v e d i r e c t i o n a l cues presented at central f i x a t i o n , s u c h as eye gaze d i r e c t i o n or h e a d orientation. These questions are left for f u t u r e studies. P e r h a p s the m o s t i m p o r t a n t i m p l i c a t i o n of f i n d i n g s r e p o r t e d here concerns the v a l i d i t y of past e x p e r i m e n t a l results r e p o r t e d i n the attentional literature o v e r the past t w o decades. O u r results demonstrate t w o v e r y i m p o r t a n t p o i n t s . First, w e replicate p r e v i o u s results i n d i c a t i n g that reflexive attentional shifts o c c u r w h e n central n o n p r e d i c t i v e cues are presented. A s s u c h these f i n d i n g s raise concerns about the o r i g i n a l d i s t i n c t i o n b e t w e e n reflexive a n d v o l u n t a r y attentional systems; a theoretical f r a m e w o r k that w a s g r o u n d e d i n distinct b e h a v i o r a l p a r a d i g m s e m p l o y i n g p e r i p h e r a l onsets a n d i n f o r m a t i v e central s t i m u l i as attentional cues. S e c o n d , o u r data demonstrate that past i n v e s t i g a t i o n s of v o l i t i o n a l attention that u s e d p r e d i c t i v e central a r r o w s t i m u l i w e r e i n fact not assessing the c o n t r i b u t i o n of v o l i t i o n a l attention alone, b u t rather a specific o r i e n t i n g response elicited b y a p r e d i c t i v e d i r e c t i o n a l cue (i.e., a r r o w ) . M o r e generally, these data cast d o u b t o n the v a l i d i t y of the classic P o s n e r p a r a d i g m , w h i c h r o u t i n e l y u s e d p r e d i c t i v e a r r o w cues, a n d , consequently, the a c c u m u l a t e d k n o w l e d g e about the p r o p e r t i e s of c o n t r o l l e d attentional processes m u c h of w h i c h has been g r o u n d e d i n this t r a d i t i o n a l e x p e r i m e n t a l p r o c e d u r e . F o r e x a m p l e , the classical p a r a d i g m s h a v e b e e n o v e r the years t y p i c a l l y a d o p t e d as a n e x p e r i m e n t a l default for n e u r o p s y c h o l o g i c a l (e.g., R a f a l & R o b e r t s o n , 1995), n e u r o i m a g i n g ( M a n g u n & H i l l y a r d , 1990; C o r b e t t a et al, 1993; H o p f i n g e r , B u o n o c o r e & M a n g u n , 2000; C o r b e t t a & S h u l m a n , 2002), a n d d e v e l o p m e n t a l (e.g., B r o d e u r & E n n s , 1997; G o l d b e r g , M a u r e r & L e w i s , 2001) investigations, a n d as s u c h h a v e been the f o u n d a t i o n o n w h i c h m u c h of the current k n o w l e d g e about h u m a n attentional processes a n d the r e s u l t i n g scientific theories of attentional operations h a v e b e e n b u i l t .  25 References B r o d e u r , D, A . & E n n s , J, T. (1997). C o v e r t v i s u a l o r i e n t i n g across the lifespan. C a n a d i a n Tournal of E x p e r i m e n t a l P s y c h o l o g y , 51, 20-35. C o r b e t t a , M . , M i e z i n , F.M., S h u l m a n , G.L., & Petersen, S.E. (1993). A P E T s t u d y of v i s u o s p a t i a l attention. J o u r n a l of N e u r o s c i e n c e , 13,1202-1226. C o r b e t t a , M & S h u l m a n , G . L. (2002). C o n t r o l of g o a l - d i r e c t e d a n d s t i m u l u s - d r i v e n attention i n the b r a i n . N a t u r e R e v i e w s : N e u r o s c i e n c e , 3, 201-215. D r i v e r , J., D a v i s , G., R i c c i a r d e l l i , P., K i d d , P., M a x w e l l , E., & B a r o n - C o h e n , S. (1999). G a z e p e r c e p t i o n triggers v i s u o s p a t i a l o r i e n t i n g b y a d u l t s i n a reflexive m a n n e r . V i s u a l Cognition, 6,509-540. Fisher, M , H . , C a s t e l , A , D., D o d d , M , D., & Pratt, J. (2003). P e r c e i v i n g n u m b e r s causes spatial shifts of attention. N a t u r e N e u r o s c i e n c e , 6, 555-556,. Friesen, C . K., & K i n g s t o n e , A . (1998). T h e eyes h a v e it!: R e f l e x i v e o r i e n t i n g is t r i g g e r e d b y n o n p r e d i c t i v e gaze. P s y c h o n o m i c B u l l e t i n a n d R e v i e w , 5,490-495. G o l d b e r g , . M . C , M a u r e r , D, & L e w i s , T, L. (2001). D e v e l o p m e n t a l changes i n attention: the effects of e n d o g e n o u s c u e i n g a n d of distractors. D e v e l o p m e n t a l Science, 4, 209-219. H o m m e l , B., Pratt, J., C o l z a t o , L. & G o d i j n , R. (2001). S y m b o l i c c o n t r o l of v i s u a l attention. P s y c h o l o g i c a l Science, 12,360-365. H o p f i n g e r , J. B., B u o n o c o r e , M . , H . , & M a n g u n , G., R. (2000). T h e n e u r a l m e c h a n i s m s of t o p - d o w n attentional c o n t r o l . N a t u r e N e u r o s c i e n c e , 3 (3), 284-291. J o h n s o n , M , H . (1997). D e v e l o p m e n t a l C o g n i t i v e N e u r o s c i e n c e . C a m b r i d g e , M A : Blackwell Publishers. J o h n s o n , M . H , Posner, M . I, & Rothbart, M . K. (1991). C o m p o n e n t s of v i s u a l o r i e n t i n g i n e a r l y infancy: C o n t i n g e n c y l e a r n i n g , a n t i c i p a t o r y l o o k i n g a n d d i s e n g a g i n g . J o u r n a l of C o g n i t i v e N e u r o s c i e n c e , 3, 335-344.  26 Jonides, J. (1981). V o l u n t a r y v e r s u s a u t o m a t i c c o n t r o l o v e r the m i n d ' s eye's m o v e m e n t . I n J. B. L o n g a n d A . D . B a d d e l e y (Eds.), A t t e n t i o n a n d P e r f o r m a n c e I X (pp. 187-203). H i l l s d a l e , N J : E r l b a u m . K i n g s t o n e , A , S m i l e k , D, Ristic, J, Friesen, C . K, & E a s t w o o d , J, D . (in press). A t t e n t i o n researchers! It is t i m e to l o o k at the real w o r l d . C u r r e n t D i r e c t i o n s i n P s y c h o l o g i c a l Science. L a n g t o n , S. R. H . , & Bruce, V . (1999). R e f l e x i v e social o r i e n t i n g . V i s u a l C o g n i t i o n , 6, 541-567. L a n g t o n , S, R, H . (2000). T h e m u t u a l i n f l u e n c e of h e a d a n d gaze o r i e n t a t i o n i n the analysis of social attention d i r e c t i o n . Q u a r t e r l y l o u r n a l of E x p e r i m e n t a l P s y c h o l o g y , 5 3 A , 825-845. L a n g t o n , S, R, H . & Bruce, V . (2000). Y o u m u s t see the p o i n t : A u t o m a t i c p r o c e s s i n g of cues to the d i r e c t i o n of social attention. l o u r n a l of E x p e r i m e n t a l P s y c h o l o g y : H u m a n P e r c e p t i o n a n d P e r f o r m a n c e , 26, 747-757. M a n g u n , G . R, & H i l l y a r d , S. A . (1990). E l e c t r o p h y s i o l o g i c a l studies of v i s u a l selective attention i n h u m a n s , In A . B. Schiebel & A . F. W e c h s l e r (Eds.) N e u r o b i o l o g y a n d H i g h e r C o g n i t i v e F u n c t i o n (pp. 271-295). N e w Y o r k , N Y : T h e G u i l f o r d Press. M u l l e r , H , J. & F i n d l a y , J, M . (1988). The effect of v i s u a l attention o n p e r i p h e r a l d i s c r i m i n a t i o n thresholds i n single a n d m u l t i p l e element d i s p l a y s . A c t a P s y c h o l o g i c a , 69,129-155. M u l l e r , H . J., & Rabbitt, P. M . A . (1989). R e f l e x i v e a n d v o l u n t a r y o r i e n t i n g of v i s u a l attention: time course of a c t i v a t i o n a n d resistance to i n t e r r u p t i o n . l o u r n a l of E x p e r i m e n t a l P s y c h o l o g y : H u m a n P e r c e p t i o n a n d P e r f o r m a n c e , 15,315-330. Posner, M . I. (1980). O r i e n t i n g of attention. Q u a r t e r l y l o u r n a l of E x p e r i m e n t a l P s y c h o l o g y , 32,3-25.  27 Posner, M , I. (1992). A t t e n t i o n as a c o g n i t i v e a n d n e u r a l s y s t e m . C u r r e n t D i r e c t i o n s i n P s y c h o l o g i c a l Science, 1,11-14. Posner, M . I., & C o h e n , Y . (1984). C o m p o n e n t s of V i s u a l O r i e n t i n g . I n H . B o u m a & D. G . B o w h u i s (Eds.), A t t e n t i o n a n d P e r f o r m a n c e X (pp. 531-556). H i l l s d a l e , N J : Erlbaum. Posner, M . I, & Petersen, (1990). T h e attention s y s t e m of the h u m a n b r a i n . A n n u a l R e v i e w of N e u r o s c i e n c e , 13, 25-42. R a f a l , R, D., C a l a b r e s i , P, A . , B r e n n a n , C , W., & Sciolto,T, K. (1989). Saccade p r e p a r a t i o n i n h i b i t s r e o r i e n t i n g to recently attended locations. Tournal of E x p e r i m e n t a l P s y c h o l o g y : H u m a n P e r c e p t i o n a n d P e r f o r m a n c e , 15, 673-685. R a f a l , R. & R o b e r t s o n , L. (1995). T h e n e u r o l o g y of v i s u a l attention. I n M . S. G a z z a n i g a (Ed.), T h e C o g n i t i v e N e u r o s i c e n c e s (pp. 625-648). C a m b r i d g e , M A : M I T Press. R e n s i n k , R. A . , (1995). V S c o p e 1.2.7, M i c r o P s y c h Software, V a n c o u v e r , B r i t i s h C o l u m b i a , C a n a d a , c o p y r i g h t 1991 - 1995. Ristic, J., Friesen, C . K., & K i n g s t o n e , A . (2002). A r e eyes special? It d e p e n d s o n h o w y o u l o o k at it. P s y c h o n o m i c B u l l e t i n a n d R e v i e w , 9,507-513. T i p p l e s , J. (2002). E y e gaze is n o t u n i q u e : A u t o m a t i c o r i e n t i n g i n response to noninformative arrows. Psychonomic Bulletin and Review.  28  CHAPTER 2  29 Introduction D e v e l o p m e n t of attentional processes p l a y s a large r o l e i n e a r l y o r g a n i z a t i o n of b e h a v i o r s u c h that it influences early c o n t r o l of a r o u s a l levels, distress m a n a g e m e n t , self-regulation as w e l l as the o r g a n i z a t i o n of early social interactions (e.g., Rothbart, P o s n e r & R o s i c k y , 1994; P o s n e r & Rothbart, 2000). B e h a v i o r a l i n v e s t i g a t i o n s of h u m a n attention i n d i c a t e that w h i l e attention generally m o v e s i n c o n j u n c t i o n w i t h eye m o v e m e n t s (overt attention), it can also be allocated to an. object or a p o s i t i o n i n space i n d e p e n d e n t l y of a shift i n gaze p o s i t i o n (covert attention) (e.g., K l e i n , K i n g s t o n e , Pontefract, 1992; K l e i n & Shore, 2000). B o t h covert a n d overt attention c a n be triggered either externally b y s t i m u l u s properties (e.g., transient abrupt-onset events) or b y i n t e r n a l goals a n d expectations of a n observer ( M u l l e r & Rabbitt, 1989; Posner, 1980; Jonides, 1981). D e v e l o p m e n t a l studies c o n d u c t e d to date i n d i c a t e that these t w o attentional systems (i.e., exogenous a n d e n d o g e n o u s , respectively) exhibit differential m a t u r a t i o n a l rates, a n d as s u c h p l a y a large role i n the d e v e l o p m e n t of relevant emergent b e h a v i o r s (e.g., H o o d , A t k i n s o n & B r a d d i k , 1998). D e v e l o p m e n t of reflexive or exogenous attention has t y p i c a l l y been investigated i n the e x p e r i m e n t a l p a r a d i g m s m a n i p u l a t i n g a b r u p t p e r i p h e r a l onsets, m i r r o r i n g those e m p l o y e d w i t h a d u l t s (e.g., Posner, 1980). W h e n reflexive o r i e n t i n g is e x a m i n e d u s i n g m a n u a l response t i m e (RT) measures i n a cross-sectional s a m p l e of c h i l d r e n , b e t w e e n ages of 5 a n d 18, the results indicate that reflexive o r i e n t i n g responses exhibit little or n o c o m p a r a t i v e change o v e r the l i f e s p a n (e.g., B r o d e u r , T r i c k & E n n s , 1997). I n contrast, studies of v o l i t i o n a l or e n d o g e n o u s attention indicate the presence of m a r k e d d e v e l o p m e n t a l differences i n the c o n t r o l of attention. Investigations of covert v o l u n t a r y attention suggest that a d u l t - l i k e c o n t r o l of attentional a l l o c a t i o n is o b s e r v e d o n l y at about 8 years of age (e.g., B r o d e u r , T r i c k & E n n s , 1997). These m a r k e d b e h a v i o r a l differences i n a l l o c a t i o n of covert reflexive a n d v o l i t i o n a l attention h a v e l a r g e l y been  30 a t t r i b u t e d to different m a t u r a t i o n a l rates of the u n d e r l y i n g b r a i n m e c h a n i s m s w h e r e reflexive attention is t h o u g h t to be c o n t r o l l e d b y earlier d e v e l o p i n g subcortical (e.g., s u p e r i o r colliculus) a n d cortical (parietal lobe) structures w h e r e a s the c o n t r o l of v o l i t i o n a l attention is a c c o m p l i s h e d b y later d e v e l o p i n g f r o n t a l cortical areas (e.g., J o h n s o n , 1997). Recently, Ristic, F r i e s e n & K i n g s t o n e (2002) r e p o r t e d that c h i l d r e n as y o u n g as 4 years of age w i l l shift their attention r e f l e x i v e l y to w h e r e a s p a t i a l l y n o n p r e d i c t i v e a r r o w is directed. A g r o u p of c h i l d r e n (mean age 4. 5 years) a n d a c o m p a r i s o n g r o u p of a d u l t s detected p e r i p h e r a l targets a p p e a r i n g to the left or r i g h t of a central s p a t i a l l y n o n p r e d i c t i v e a r r o w cue. A t t e n t i o n a l o r i e n t i n g w a s s a m p l e d at t e m p o r a l intervals of 195,600, a n d 1000 m s . T h e results r e v e a l e d that, o v e r a l l , b o t h g r o u p s r e s p o n d e d faster to c u e d c o m p a r e d to u n c u e d targets. T h i s effect a p p e a r e d less t h a n 200 m s after the a r r o w cue w a s p r e s e n t e d a n d it persisted, a n d g r e w i n m a g n i t u d e , as the cue-target S O A w a s e x t e n d e d to a p p r o x i m a t e l y 1000 m s . T h i s f i n d i n g contrasts w i t h the o n l y other i n v e s t i g a t i o n that has s t u d i e d the effect of central a r r o w cues o n attentional o r i e n t i n g i n s u c h y o u n g c h i l d r e n . B r o d e u r a n d E n n s (1997, E x p e r i m e n t 1) a s k e d three g r o u p s of c h i l d r e n ( m e a n ages of 6,8, a n d 10 years) to i d e n t i f y a target (X or O ) that a p p e a r e d either near to, or far f r o m , a central a r r o w cue. T h i s a r r o w cue correctly i n d i c a t e d the target h e m i f i e l d o n 80% of the trials (i.e., it w a s s p a t i a l l y p r e d i c t i v e ) . O r i e n t i n g effects w e r e e x a m i n e d at S O A s o f 133,250 a n d 450 m s . W h i l e a d u l t s s h o w e d significant o r i e n t i n g effects ( U n c u e d - C u e d R T ) for a l l cue-target intervals, c h i l d r e n s h o w e d significant o r i e n t i n g effects for 133 m s S O A o n l y . In contrast to the Ristic et al. (2002) s t u d y , the c u i n g effect for the y o u n g e s t g r o u p of c h i l d r e n d e c l i n e d as the S O A increased, d i s a p p e a r i n g altogether b y the 500 m s S O A . B a s e d o n these data, the authors a r g u e d that c h i l d r e n 6 years of age w e r e able to orient attention v o l i t i o n a l l y i n response to the p r e d i c t i v e nature of a central a r r o w cue, b u t o n l y for a  31 short p e r i o d of time. Subsequent studies s h o w e d that after age 8, l i k e adults, c h i l d r e n are able to s u s t a i n v o l i t i o n a l o r i e n t i n g for longer d u r a t i o n s ( G o l d b e r g , M a u r e r & L e w i s , 2001). Insofar as these t w o studies can be attributed to reflexive a n d v o l i t i o n a l attention respectively, the i m p l i c a t i o n is that for y o u n g c h i l d r e n reflexive o r i e n t i n g is r a p i d a n d l o n g - l a s t i n g a n d v o l i t i o n a l o r i e n t i n g is r a p i d a n d s h o r t - l i v e d (the latter interpretation b e i n g f a v o r e d b y B r o d e u r & Enns). H o w e v e r , as w e h a v e s h o w n i n C h a p t e r 1, there are v e r y g o o d reasons to q u e s t i o n the interpretation of studies that h a v e e m p l o y e d p r e d i c t i v e a r r o w cues, as it w a s u s e d b y B r o d e u r & E n n s (1997). T h e attention effect they o b s e r v e d w i t h a p r e d i c t i v e a r r o w cue c o u l d reflect r e f l e x i v e attention, v o l i t i o n a l attention, or s o m e c o m b i n a t i o n of the t w o . N e v e r t h e l e s s , the fact r e m a i n s that the B r o d e u r & E n n s (1997) s t u d y suggests that p r e d i c t i v e a r r o w cues p r o d u c e a v e r y different p a t t e r n of results t h a n w h a t w a s o b s e r v e d for a d u l t s i n C h a p t e r 1. Specifically, w h e r e the attention effect for p r e d i c t i v e a r r o w s g r e w for a d u l t s as the cue-target i n t e r v a l e x t e n d e d across time, the effect d e c l i n e d for c h i l d r e n i n the B r o d e u r a n d E n n s ' (1997) i n v e s t i g a t i o n . W h e t h e r this effect s h o u l d be a t t r i b u t e d to s h o r t - l i v e d v o l i t i o n a l attention, or a c o m b i n a t i o n of reflexive a n d v o l i t i o n a l attention that is v e r y different f r o m w h a t w a s o b s e r v e d for adults, is v e r y m u c h a n o p e n question. In C h a p t e r 2 w e a d d r e s s e d this issue d i r e c t l y b y e m p l o y i n g the l o g i c u s e d successfully i n C h a p t e r 1, w h e r e b y w e dissociated o r i e n t i n g responses of y o u n g c h i l d r e n to s p a t i a l l y p r e d i c t i v e a n d n o n p r e d i c t i v e d i r e c t i o n a l (arrow) a n d n o n d i r e c t i o n a l (shape) central attentional cues. Experiment 1 In o r d e r to e x a m i n e this issue, first w e presented a g r o u p of y o u n g c h i l d r e n a n d a g r o u p of a d u l t s w i t h a c u i n g task i n w h i c h central d i r e c t i o n a l a r r o w cues s e r v e d as f i x a t i o n s t i m u l i . Further, to assess w h e t h e r the o r i e n t i n g t r i g g e r e d b y s p a t i a l l y  32 p r e d i c t i v e a r r o w cues i n d e e d reflected v o l u n t a r y o r i e n t i n g , i n a subsequent m a n i p u l a t i o n w e c o m p a r e d o r i e n t i n g i n y o u n g c h i l d r e n a n d a d u l t s i n response to central geometric shape cues. Instead of u s i n g d i g i t cues as e m p l o y e d i n C h a p t e r 1, here w e u t i l i z e d central geometric shape (circle or square) as a s y m b o l i c target l o c a t i o n p r e d i c t o r i n o r d e r to equate f a m i l i a r i t y w i t h the cue b e t w e e n y o u n g c h i l d r e n a n d a d u l t s . T h i s n o n d i r e c t i o n a l cue m a n i p u l a t i o n represents a c r u c i a l test of w h e t h e r the attentional o r i e n t i n g i n response to p r e d i c t i v e a r r o w cues i n c h i l d r e n is i n d i c a t i v e of v o l u n t a r y o r i e n t i n g or not. B o t h d i r e c t i o n a l (arrow) a n d n o n d i r e c t i o n a l (shape) cues w e r e presented as either n o n p r e d i c t i v e (p=. 5) or p r e d i c t i v e (p=. 8) of the target l o c a t i o n . A l l m a n i p u l a t i o n s w e r e c a r r i e d o u t b e t w e e n subjects s u c h that each cue t y p e b y cue predictiveness c o n d i t i o n w a s c a r r i e d out o n a separate g r o u p of p a r t i c i p a n t s i n each age g r o u p . I n o r d e r to ensure that w e w e r e i n fact e x a m i n i n g covert o r i e n t i n g responses eye movements were monitored i n all experimental conditions. Method Participants A total of 60 c h i l d r e n a n d 60 u n d e r g r a d u a t e students p a r t i c i p a t e d i n the present s t u d y . Fifteen c h i l d r e n a n d 15 a d u l t s w e r e a s s i g n e d to each of the cue type x cue predictiveness c o n d i t i o n s (arrow n o n p r e d i c t i v e ; a r r o w p r e d i c t i v e ; shape n o n p r e d i c t i v e ; s h a p e p r e d i c t i v e ) . T h e ages for the c h i l d r e n i n each of the f o u r c o n d i t i o n s w e r e : (1) n o n p r e d i c t i v e a r r o w c o n d i t i o n (9 males) 3 years, 5 m o n t h s to 6 years, 2 m o n t h s (mean age 4 years, 5 m o n t h s ) ; (2) p r e d i c t i v e a r r o w c o n d i t i o n (8 males) 4 years, 11 m o n t h s to 5 years, 11 m o n t h s of age (mean age 5 years, 3 months); (3) n o n p r e d i c t i v e shape c o n d i t i o n (7 males) 3 years, 5 m o n t h s to 5 years, 4 m o n t h s (mean age 4 years, 3 m o n t h s ) ; (4) p r e d i c t i v e shape c o n d i t i o n (9 males) 3 years, 4 m o n t h s to 4 years, 9 m o n t h s (mean age 4 years, 4 m o n t h s ) . A l l c h i l d r e n w e r e recruited f r o m local V a n c o u v e r D a y c a r e Centers  33 w i t h the i n f o r m e d consent of the parents a n d the daycare centers. U n d e r g r a d u a t e students w e r e r e c r u i t e d f r o m U B C P s y c h o l o g y Subject P o o l , a n d a l l observers c o m p l e t e d the e x p e r i m e n t i n exchange for course credit. Apparatus and Stimuli T h e s t i m u l i w e r e presented o n a M a c i n t o s h P o w e r b o o k 3200c l a p t o p c o m p u t e r connected to a n external k e y b o a r d . The s t i m u l i w e r e p r e s e n t e d o n a 12-inch L C D color screen set to b l a c k a n d w h i t e . V S c o p e 1.2.7 software (Rensink, 1995) w a s u s e d to c o n t r o l s t i m u l u s presentation a n d r e c o r d response latencies a n d accuracies. Participants r e s p o n d e d b y p r e s s i n g the spacebar k e y o n the external k e y b o a r d , p o s i t i o n e d i n front of the c o m p u t e r , w h i c h w a s m a r k e d w i t h r e d tape to r e m i n d c h i l d r e n of correct response k e y . E y e m o v e m e n t s w e r e m o n i t o r e d on-line b y the e x p e r i m e n t e r u s i n g a n external m i r r o r p o s i t i o n e d a b o v e the c o m p u t e r screen. T h e s t i m u l i a n d sequence of events are p r e s e n t e d i n F i g u r e 1. A l l s t i m u l i w e r e b l a c k line d r a w i n g s presented o n a w h i t e b a c k g r o u n d . T h e a r r o w s t i m u l u s w a s created b y attaching a n a r r o w h e a d a n d a n a r r o w t a i l (each 45-degree o r i e n t e d line m e a s u r e d 0.6°) to the b o t h ends of a h o r i z o n t a l line m e a s u r i n g 1.3° i n l e n g t h . T h e a r r o w s t i m u l u s w a s 2.5° l o n g as m e a s u r e d f r o m the tip of the a r r o w h e a d to the e n d of the a r r o w t a i l , a n d it w a s a l w a y s p o s i t i o n e d at the center of the screen. I n a n o n d i r e c t i o n a l cue c o n d i t i o n , one of t w o g e o m e t r i c a l shape cues, line d r a w i n g s of a circle a n d a square, s e r v e d as central f i x a t i o n s t i m u l i . T h e circle a n d square b o t h m e a s u r e d 1.9° i n l e n g t h a n d height. A s m a l l central cross ( s u b t e n d i n g 1° v i s u a l angle), s e r v e d as a f i x a t i o n p o i n t i n the n o n d i r e c t i o n a l cue c o n d i t i o n s . T h e response target w a s a b l a c k asterisk s u b t e n d i n g 0.7°. T h e target a l w a y s a p p e a r e d 5° to the left or r i g h t of center as m e a s u r e d f r o m the center of the cue to center of the target.  34  Directional Cue  Nondirectional Cue  675 ms  +  CD  E Cue Onset  100 or 900 ms SOA  > — >  *  Target O n s e t until response or 2300ms  Figure 1 illustrates stimuli and timing sequence for directional (arrow and nondirectional (geometric shape) cue conditions. A straight line or a fixation point appeared on the screen for 675 ms. Then, an arrow pointing left or right, or central circle or square appeared on the screen. The target appeared centered across horizontal meridian, either on the left or right side of the cue after 100 on 900 ms. Both the cue and the target remained on the screen until response was made or for 2700ms, whichever came first. Intertrial interval was 516 ms. Note that the stimuli are not drawn to scale.  Design For the nonpredictive cue condition, the target location was unrelated to the cue. For instance, in the arrow cue condition, the left or right direction of the arrow was randomly determined as was the left or right location of the target. Thus, the target could appear at the cued location (location pointed at by the arrow) or at the uncued location (location not pointed at by the arrow) with a probability equal to chance (p=. 5). Similarly, for nondirectional shape cue, the cue was either a circle or a square, and the location of the target was unrelated to the type of shape cue. For the predictive arrow cue condition, the arrow direction was again chosen at random, but now the target  35 a p p e a r e d at the l o c a t i o n c u e d b y the a r r o w m o s t of the t i m e (p=. 8) a n d occasionally at the u n c u e d l o c a t i o n (p=. 2). S i m i l a r l y , for the shape cue c o n d i t i o n , one shape i n d i c a t e d that the target w a s l i k e l y to appear o n the left (p=. 8) a n d the other shape i n d i c a t e d that the target w a s l i k e l y to appear o n the r i g h t (p=. 8). The o r d e r of w h i c h shape i n d i c a t e d w h i c h side w a s c o u n t e r b a l a n c e d across participants. T h e t i m e c o u r s e of attentional a l l o c a t i o n w a s e x a m i n e d b y s a m p l i n g the p e r f o r m a n c e at t w o cue-target s t i m u l u s onset a s y n c h r o n i e s ( S O A s ) : 100 a n d 900 m s . The t w o d e l a y intervals w e r e d i s t r i b u t e d e q u a l l y t h r o u g h o u t the experiment. In a d d i t i o n , i n a p p r o x i m a t e l y 6% of a l l trials the target w a s not presented. These catch trials w e r e r a n d o m l y seeded t h r o u g h o u t the experiment. E a c h p a r t i c i p a n t , except the t w o c h i l d r e n w h o c o m p l e t e d o n l y one b l o c k i n response to n o n p r e d i c t i v e shape, c o m p l e t e d a total of 100 e x p e r i m e n t a l trials that w e r e d i v i d e d i n t w o b l o c k s of 50 trials each. A l l participants, except one c h i l d , c o m p l e t e d the t w o b l o c k s of trials i n succession. A practice b l o c k of about 10 trials w a s r u n at the b e g i n n i n g of the e x p e r i m e n t a l session. A failure to e m p h a s i z e response s p e e d (mean detection R T greater t h a n 500 m s for a d u l t s a n d 900 m s for c h i l d r e n ) resulted i n 1 a d u l t and 2 children being replaced. Procedure A l l trials b e g a n w i t h the presentation of a straight l i n e or a f i x a t i o n cross for 675 m s . T h e n , i n the a r r o w c o n d i t i o n , a n a r r o w h e a d a n d a n a r r o w t a i l a p p e a r e d at b o t h ends of the line to create a n a r r o w p o i n t i n g left or right. In the n o n d i r e c t i o n a l cue c o n d i t i o n , center shape, either a circle or a square, a p p e a r e d at the center of the screen. A f t e r 100 or 900 m s the target a p p e a r e d o n either left or r i g h t side of the screen. E a c h trial t e r m i n a t e d o n response, or after 2300 m s w h i c h e v e r came first. T h e i n t e r t r i a l i n t e r v a l w a s 516 m s .  36 A l l c h i l d r e n w e r e tested at a daycare facility. T w o e x p e r i m e n t e r s w e r e present w i t h the c h i l d r e n at a l l times. O n e experimenter sat beside the c h i l d a n d e n s u r e d that each p a r t i c i p a n t w a s r e s p o n d i n g w i t h the p r o p e r key. T h e other experimenter w a s p o s i t i o n e d b e h i n d the p a r t i c i p a n t a n d r e c o r d e d eye m o v e m e n t s b y o b s e r v i n g p a r t i c i p a n t s eyes i n the m i r r o r a n d the e x p e r i m e n t a l sequence o n the screen. O n every trial, the e x p e r i m e n t e r j u d g e d w h e t h e r a n eye m o v e m e n t h a d o c c u r r e d a n d if it d i d the e x p e r i m e n t e r r e c o r d e d the trial n u m b e r o n w h i c h the saccade w a s m a d e . E y e m o v e m e n t s that w e r e m a d e either i n a n t i c i p a t i o n of the target p o s i t i o n or saccades that w e r e m a d e to the target w h e n it a p p e a r e d o n the screen w e r e r e c o r d e d . A f t e r a g r e e i n g to take part i n the s t u d y , the c h i l d r e n sat i n front of the c o m p u t e r a n d w e r e centered w i t h respect to the screen a n d k e y b o a r d ( v i e w i n g distance a p p r o x i m a t e l y 57 centimeters). The c h i l d r e n w e r e then t o l d h o w the s t u d y w a s g o i n g to p r o c e e d . I n a l l c o n d i t i o n s c h i l d r e n w e r e a s k e d to " c a t c h the s n o w f l a k e " as fast as they c o u l d w h e n it a p p e a r e d o n the screen b y p r e s s i n g the r e d k e y o n the k e y b o a r d . T h e y w e r e t o l d that they w o u l d see either a n a r r o w or circle or square presented at the center of the screen before the s n o w f l a k e a p p e a r e d . I n the n o n p r e d i c t i v e cue conditions, the c h i l d r e n w e r e i n f o r m e d that a r r o w d i r e c t i o n (or shape) d i d n o t i n d i c a t e w h e r e the s n o w f l a k e w o u l d appear. I n the p r e d i c t i v e cue c o n d i t i o n s , the c h i l d r e n w e r e i n f o r m e d that a r r o w d i r e c t i o n w o u l d i n f o r m t h e m about s n o w f l a k e ' s l o c a t i o n m o s t of the time. S i m i l a r l y , for the p r e d i c t i v e s h a p e c u e c o n d i t i o n c h i l d r e n w e r e i n f o r m e d a b o u t the p r e d i c t i v e r e l a t i o n s h i p b e t w e e n the cue a n d the l i k e l y target l o c a t i o n . T h e experimenter e n s u r e d that a l l c h i l d r e n u n d e r s t o o d instructions f u l l y before c o m m e n c i n g the experiment. U n d e r g r a d u a t e students w e r e tested i n the laboratory. E x p e r i m e n t a l p r o c e d u r e a n d instructions p a r a l l e l e d those e m p l o y e d w i t h c h i l d r e n , w i t h one exception that o n l y one e x p e r i m e n t e r w a s present i n the testing r o o m at a l l times.  37 Results M e d i a n R T w a s calculated for each participant. T h e i n t e r p a r t i c i p a n t m e a n R T s for b o t h age g r o u p s are i l l u s t r a t e d i n F i g u r e 2 a n d p r e s e n t e d i n Table 1 for adults a n d Table 2 for c h i l d r e n . Incorrect k e y presses, t i m e d - o u r responses, a n d false alarms c o u n t e d as errors a n d w e r e r e m o v e d f r o m the analysis. Table 3 presents o v e r a l l error rates as w e l l as saccadic eye m o v e m e n t rate . 1  Arrow Condition*  Shape  nonpredictive  M  SD  predictive  SD  M  nonpredictive  M  SD  predictive  M  SD  100 ms S O A Cued  385.5  67.3  415.2  93.3  400.5  83.2  379.2  68.5  Uncued  389.9  53.6  442.9  95.9  397.9  82  391.8  74.6  Cued  337.9  47.7  343.6  66.2  358.7  47  336  47.4  Uncued  351.1  54.4  389  99  353.5  47.5  352.1  52.1  900 ms S O A  Table 1. Mean RTs and standard deviations for adults. *Since there was no true "cued" and "uncued" target conditions in nonpredictive shape condition, corresponding numbers represent mean RTs for targets appearing on the left and right side location for the two S O A intervals.  In order to ensure that we were measuring covert attention, number of recorded eye movements made either to the target or i n anticipation of the target was included a covariate in preliminary analyses. Saccadic eye movements did not account for significant variation present in the data, and as such d i d not change reported results. A l l analyses reported here show actual p values without eye movement rate included as a covariate. 1  38  Arrow Condition*  nonpredictive  predictive  SD  M  Shape  M  SD  nonpredictive  M  SD  predictive  M  SD  100 ms SOA Cued  680.6  153  685.4  153.5  795.4  211.7  726.4  145.3  Uncued  686.8  136.6  724.2  168.5  780  207  773  208.7  Cued  603.9  93.7  585.2  93.6  671.3  175  643.6  128.3  Uncued  630.8  118.74  618.3  146.3  711.7  212.6  646.1  149  900 ms SOA  Table 2. Mean RTs and standard deviations for children. *Since there was no true "cued" and "uncued" target conditions in nonpredictive shape condition, corresponding numbers represent mean RTs for targets appearing on the left or right side locations for the two SOA intervals.  Adults Condition  TO  FA  IK  Children EM  TO  IK  FA  EM  Arrow . 45%  0  1. 12%  2. 5%  3. 4%  . 64%  25.8%  5%  Predictive  0  0  2. 2%  3. 4%  3. 3%  . 14%  19. 3%  8%  Nonpredictive  0  0  2. 2%  2%  4. 4%  .2%  24%  6.1%  Predictive  0  0  0  3. 5%  1. 7%  . 28%  25. 6%  7. 3%  Nonpredictive  Shape  Table 3. Error rates and eye movement rates for all conditions. TO (timed out responses), IK (incorrect key presses), FA (false alarms), E M (eye movements).  39  ADULTS  CHILDREN  A:Directional Cue 505  820r  predictive arrow  nonpredictive arrow  r  772  457  cu E ic o  409  \  361  •  ID CU  •  1  100  1  •  900  100  676  \  N \  *  628  "u 580  I  100  900  SOA  SOA  \ \  a: c ID CU  \  724  '•rj  313  265  predictive arrow  nonpredictive arrow  900  . \  100  900  SOA  SOA  uncued cued  B:Nondirectional Cue 505  820  predictive shape  nonpredictive shape  g  457  ID CU  j! c o ti  s  361  \  724  676  ID  a: c ID CU  \  cu  <u E i- 4 0 9 c o ti  predictive shape  nonpredictive shape  772  & 313  cu •  265 100  i  100  900  900  SOA  SOA  i  580  •  i  100  900  SOA  I  •  100  900  SOA  Cuing Effects  100  900  predictive arrow  SOA  predictive shape —M—  nonpredictive arrow  Figure 2 shows results from Experiment 1. Results from two age groups are presented on the left (adults) and on the right (children). Figure 2a shows mean response times (RTs) plotted as a function of S O A and validity for nonpredictive and predictive directional arrow cues for both age groups. Figure 2b shows mean response times for nonpredictive and predictive central shape cues, with only an S O A effect plotted for nonpredictive shape condition. Figure 2c plots the difference between uncued and cued RTs for both adults (left panel) and children (right panel).  40  T h e results for the n o n p r e d i c t i v e a r r o w c o n d i t i o n (see F i g u r e 2a) w e r e a n a l y z e d u s i n g a t h r e e - w a y A N O V A w h e r e age g r o u p ( c h i l d r e n a n d adults) w a s i n c l u d e d as a between-subject factor, a n d S O A a n d v a l i d i t y w e r e w i t h i n - s u b j e c t factors. T h e analysis i n d i c a t e d that a l l m a i n effects w e r e significant: g r o u p [F (1,28)= 88.92, p < .0001], S O A [F (1,28)= 28.02, p < . 0001], a n d v a l i d i t y [F (1,28)= 4.43, p < . 05]; a n d that n o interactions w e r e significant [all ps>. 05]. These f i n d i n g s reflect the fact that w h i l e c h i l d r e n w e r e s l o w e r o v e r a l l to r e s p o n d to targets t h a n adults, the effects of S O A a n d cue c o n d i t i o n w e r e s i m i l a r for b o t h age g r o u p s . Specifically, R T d e c l i n e d as S O A increased, reflecting a classic f o r e p e r i o d effect; a n d R T w a s shorter for c u e d t h a n u n c u e d locations at b o t h S O A s reflecting the fact that attention w a s shifted r e f l e x i v e l y to the l o c a t i o n i n d i c a t e d b y a s p a t i a l l y n o n p r e d i c t i v e a r r o w cue as r e p o r t e d p r e v i o u s l y b y Ristic et al. (2002). M e d i a n correct R T s for the t w o age g r o u p s that r e c e i v e d p r e d i c t i v e a r r o w cues w e r e subjected to the same t h r e e - w a y A N O V A . T h i s a n a l y s i s also r e t u r n e d three significant m a i n effects: age g r o u p [F (1, 28)= 42.78, p < . 0001], S O A [F (1, 28)= 25.34, p < .0001], a n d v a l i d i t y [F (1, 28)= 27.88, p < .0001]. N o interactions b e t w e e n g r o u p a n d v a l i d i t y w e r e o b s e r v e d [all ps> .05]. A s the F i g u r e 2a illustrates, b o t h age g r o u p s p r o d u c e d s i m i l a r b e h a v i o r a l responses w h e n presented w i t h p r e d i c t i v e a r r o w cues. W h i l e c h i l d r e n w e r e o v e r a l l s l o w e r , b o t h age g r o u p s r e s p o n d e d faster as the time b e t w e e n the cue onset a n d target presentation increased. F u r t h e r m o r e , b o t h age w e r e faster to r e s p o n d to targets a p p e a r i n g at the p r e d i c t e d l o c a t i o n for b o t h short a n d l o n g S O A intervals. I n s u m m a r y , the data for the a r r o w cue c o n d i t i o n s i n d i c a t e that b o t h c h i l d r e n a n d a d u l t s detected c u e d targets faster t h a n u n c u e d targets regardless of w h e t h e r the central a r r o w cue w a s s p a t i a l l y p r e d i c t i v e or not. I n contrast to n o n p r e d i c t i v e a r r o w cues, n o n p r e d i c t i v e shape cues w e r e not effective i n e l i c i t i n g reflexive o r i e n t i n g i n either age g r o u p . Interparticipant means of  41 m e d i a n R T s calculated for each g r o u p of p a r t i c i p a n t s w e r e subjected to the subsequent analyses for n o n d i r e c t i o n a l shape c o n d i t i o n . T h e y are i l l u s t r a t e d i n F i g u r e 2b. A f o u r - w a y A N O V A that i n c l u d e d age g r o u p as a between-subject variable, S O A , c u e t y p e (circle o r square), a n d target p o s i t i o n (left o r right), as within-subject variables i n d i c a t e d that a g a i n o v e r a l l c h i l d r e n r e s p o n d e d s l o w e r t h a n a d u l t s [F (1,28)= 66.67, p < . 0001] a n d that o n average b o t h age g r o u p s r e s p o n d e d faster as the S O A i n t e r v a l l e n g t h e n e d [F (1, 28)= 14.02, p < . 001]. S O A x cue t y p e x age g r o u p interaction w a s also significant [F (1,28)= 4.92, p < . 05] reflecting that at the 900 m s S O A c h i l d r e n generated faster responses w h e n the central cue w a s a circle t h a n w h e n it w a s a square. I m p o r t a n t l y , h o w e v e r , cue type d i d not interact w i t h target p o s i t i o n [F<1] i n d i c a t i n g that the shape cues d i d not trigger a n y specific d i r e c t i o n a l o r i e n t i n g effects i n either age g r o u p . T h u s , shape cues represent a v a l i d c o m p a r i s o n set against w h i c h a n y c o n t r i b u t i o n of v o l u n t a r y attention can be assessed w h e n the same cues are m a n i p u l a t e d as s p a t i a l l y p r e d i c t i v e of target location. T h e d a t a for b o t h age g r o u p s are i l l u s t r a t e d i n F i g u r e 2b, s h o w i n g m e a n R T s as a f u n c t i o n of S O A . D a t a for p r e d i c t i v e shape cues w e r e a n a l y z e d u s i n g a t h r e e - w a y A N O V A , w i t h age g r o u p as between-subject variable, a n d S O A a n d v a l i d i t y as within-subject variables. T h e a n a l y s i s r e t u r n e d significant m a i n effects of g r o u p [F (1, 28)= 64.01, p < . 0001] a n d S O A [F (1, 28)= 46.69, p < . 0001] as w e l l as a significant S O A x g r o u p interaction [F (1,28)= 8.75, p < .01] reflecting a larger d e c l i n e i n R T s across S O A s (the f o r e p e r i o d effect) for c h i l d r e n . T h e v a l i d i t y effect w a s m a r g i n a l l y s i g n i f i c a n t [F (1,28)= 4.15, p < .052] as w a s the three-way interaction b e t w e e n age g r o u p , S O A , a n d v a l i d i t y [F (1, 28)= 3.3, p < . 07]. F o u r d i r e c t i o n a l p a i r e d t-tests w e r e c o n d u c t e d to c o m p a r e m e a n R T for c u e d a n d u n c u e d c o n d i t i o n s across b o t h S O A i n t e r v a l s for a d u l t s a n d c h i l d r e n . The analysis i n d i c a t e d that, i n d e e d , significant o r i e n t i n g effects w e r e present at b o t h S O A s  42 of 100 a n d 900 m s for a d u l t s a n d o n l y at a n early S O A of 100 m s for c h i l d r e n [all ps <. 05]. Discussion T h e r e are several f i n d i n g s w o r t h n o t i n g i n the present i n v e s t i g a t i o n . First, the data w i t h n o n p r e d i c t i v e a r r o w cues replicated those r e p o r t e d b y Ristic, Friesen & K i n g s t o n e (2002), d e m o n s t r a t i n g a g a i n that c h i l d r e n a n d a d u l t s a l i k e w i l l shift their attention to the l o c a t i o n i n d i c a t e d b y a n o n p r e d i c t i v e a r r o w cue. A l s o i n agreement w i t h Ristic et al (2002), it w a s o b s e r v e d that w i t h a n o n p r e d i c t i v e a r r o w cue the difference b e t w e e n c u e d a n d u n c u e d target locations tends to g r o w for c h i l d r e n as the cue-target S O A is increased. S e c o n d , a n d i n agreement w i t h B r o d e u r a n d E n n s (1997), the present s t u d y f o u n d that w h e n the a r r o w cue w a s p r e d i c t i v e , a l t h o u g h b o t h c h i l d r e n a n d adults p r o d u c e d s i m i l a r p e r f o r m a n c e patterns, the effect of the cue d e c l i n e d substantially across S O A s for c h i l d r e n , b u t the effect of the cue increased across S O A s for adults. T h i r d , b y c o m p a r i n g these p e r f o r m a n c e s w i t h n o n p r e d i c t i v e a n d p r e d i c t i v e a r r o w cues against p e r f o r m a n c e w i t h a p r e d i c t i v e n o n d i r e c t i o n a l shape cue, several i m p o r t a n t i n s i g h t s r e g a r d i n g attentional o r i e n t i n g w e r e r e v e a l e d . F o r adults, the c u i n g effect for a p r e d i c t i v e a r r o w cue w a s f o u n d to exceed w h a t w o u l d be expected b y a d d i n g the reflexive attentional effect p r o d u c e d b y a n o n p r e d i c t i v e a r r o w cue a n d the v o l i t i o n a l attentional effect p r o d u c e d b y a p r e d i c t i v e shape cue. A s w a s r e p o r t e d p r e v i o u s l y i n C h a p t e r 1, reflexive a n d v o l i t i o n a l c o m p o n e n t s a p p e a r to interact to p r o d u c e a larger c u i n g effect for p r e d i c t i v e a r r o w s t h a n w o u l d be expected based o n p u r e measures of the t w o c o m p o n e n t s alone. In contrast, for c h i l d r e n w e f o u n d that the v o l i t i o n a l attention effect for a shape cue w a s significant o n l y at the 100 ms, consistent w i t h the p r o p o s a l of B r o d e u r a n d E n n s (1997) that this f o r m of o r i e n t i n g c a n o n l y be s u s t a i n e d b r i e f l y b y c h i l d r e n y o u n g e r t h a n 8 years of age. M o r e o v e r , a n d a g a i n i n  43  contrast w i t h adults, it appears that the cuing effect of a predictive arrow reflects precisely what w o u l d be expected by adding the reflexive attentional effect produced by a nonpredictive arrow cue and the volitional attentional effect produced by a predictive shape cue (see Figure 2c). Indeed, it appears that the cuing effect observed for children w i t h a predictive arrow at the 900ms S O A reflects the residual presence of reflexive orienting, as there is no volitional component present at this long S O A for a predictive shape cue, and the cuing effect for a predictive arrow converges w i t h the cuing effect of a nonpredictive arrow. To summarize, our data demonstrate that reflexive attention operates i n a very similar manner for adults and children, but that endogenous attention operates and combines w i t h reflexive attention differently between these two groups. Adults can orient attention endogenously for a sustained period of time; and when this form of orienting is combined w i t h reflexive attention to a directional stimulus, the results is a superadditive interaction for predictive arrow cues. Children younger than 6 years, on the other hand, can also orient attention endogenously, but only for a brief period of time; and when this form of orienting is combined w i t h reflexive attention to a direction stimulus, the two effects are additive. This finding suggests that the superadditive interaction w i t h predictive arrow cues, that is observed w i t h adults but not with children, may depend on the development of sustained, adult-like, volitional orienting. These similarities and differences between adults and children as a function of type of attentional orienting dovetail with the fields' current understanding of the maturation of the brain areas that subserve reflexive and volitional orienting. Research results to date indicate that because reflexive orienting is mediated by early developing subcortical and cortical brain areas, such as the superior colliculus and the parietal lobe, its presence can be behaviorally measured shortly after birth (e.g., Clohessy, Posner, Rothbart & Vecera, 1991; Johnson, Posner & Rothbart, 1991; Valenza, Simion & Umilta,  44 1994). M o r e o v e r , w h e n p e r f o r m a n c e of a d u l t s a n d y o u n g c h i l d r e n is c o m p a r e d b e h a v i o r a l l y i n a c u i n g p a r a d i g m , little or n o differences are o b s e r v e d b e t w e e n the t w o g r o u p s of p a r t i c i p a n t s (Enns & B r o d e u r , 1989; B r o d e u r , T r i c k & E n n s , 1997; Ristic et al, 2002). I n contrast to reflexive o r i e n t i n g , v o l u n t a r y attention d e v e l o p s m u c h s l o w e r a n d exhibits a d u l t - l i k e properties o n l y a b o u t 8 years of age (e.g., B r o d e u r , T r i c k & E n n s , 1997; G o l d b e r g , M a u r e r & L e w i s , 2001). T h i s agrees w i t h the n o t i o n that c o n t r o l l e d attention is m e d i a t e d b y m e c h a n i s m s r e s i d i n g w i t h i n the f r o n t a l cortex (e.g., C o r b e t t a & S h u l m a n , 2002), a b r a i n r e g i o n that matures m o r e s l o w l y t h a n the p a r i e t a l cortex o r the s u p e r i o r c o l l i c u l u s (Johnson, 1997). R u d i m e n t a r y c o n t r o l of v o l i t i o n a l attention c a n be o b s e r v e d i n infancy, w i t h n e w b o r n s able to m a k e a n t i c i p a t o r y saccades t o w a r d s the interesting objects i n the e n v i r o n m e n t (e.g., J o h n s o n , P o s n e r & Rothbart, 1991; H o o d , A t k i n s o n & B r a d d i k , 1998; Posner, 2001). H o w e v e r , w h e n v o l i t i o n a l o r i e n t i n g is e x a m i n e d u s i n g attentional c u i n g tasks, the results r e p o r t e d here a n d i n the literature, i n d i c a t e that at age 6 years v o l u n t a r y o r i e n t i n g is s t i l l too i m m a t u r e to p r o d u c e a n y t h i n g b u t s h o r t - l i v e d o r i e n t i n g effects that q u i c k l y decrease i n m a g n i t u d e over time ( B r o d e u r & E n n s , 1997).  45 References B r o d e u r , A . , D., Trick, M . , I, & E n n s , J. T. (1997). Selective attention o v e r the lifespan. I n B u r a c k A . J. & E n n s J. T. (Eds.). A t t e n t i o n , D e v e l o p m e n t , a n d P s y c h o p a t h o l o g y (pp. 74-97). N e w Y o r k : G u i l f o r d Press. B r o d e u r , D, A . & E n n s , J, T. (1997). C o v e r t v i s u a l o r i e n t i n g across the lifespan. C a n a d i a n Tournal of E x p e r i m e n t a l P s y c h o l o g y , 51, 20-35. C l o h e s s y , A . B, Posner, M . I, & Rothbart, M , K., & V e c e r a (1991). T h e d e v e l o p m e n t of i n h i b i t i o n of r e t u r n i n early infancy. l o u r n a l of C o g n i t i v e N e u r o s c i e n c e , 3, 345-351. C o r b e t t a , M & S h u l m a n , G . L. (2002). C o n t r o l of goal-directed a n d s t i m u l u s - d r i v e n attention i n the b r a i n . N a t u r e R e v i e w s : N e u r o s c i e n c e , 3, 201-215. E n n s , J. T, & B r o d e u r , D, A . (1989). A d e v e l o p m e n t a l s t u d y of covert o r i e n t i n g to p e r i p h e r a l v i s u a l cues. l o u r n a l of E x p e r i m e n t a l C h i l d P s y c h o l o g y , 48,171-189. G o l d b e r g , M . C , M a u r e r , D, & L e w i s , T. L. (2001). D e v e l o p m e n t a l changes i n attention: the effects of e n d o g e n o u s c u e i n g a n d of distractors. D e v e l o p m e n t a l Science, 4, 209-219. H o o d , B. M , A t k i n s o n , J, & B r a d d i k , O . J. (1998). Selection-for-action a n d the d e v e l o p m e n t of o r i e n t i n g a n d v i s u a l attention, I n J. E. R i c h a r d s (Ed.), C o g n i t i v e neuroscience of attention: A D e v e l o p m e n t a l perspective (pp. 219-251). N e w Jersey: Erlbaum. J o h n s o n , M . H . (1997). D e v e l o p m e n t a l C o g n i t i v e N e u r o s c i e n c e . C a m b r i d g e , M A : Blackwell Publishers. J o h n s o n , M . H , Posner, M . I, & Rothbart, M . K. (1991). C o m p o n e n t s of v i s u a l o r i e n t i n g i n early infancy: C o n t i n g e n c y l e a r n i n g , a n t i c i p a t o r y l o o k i n g a n d d i s e n g a g i n g . Tournal of C o g n i t i v e N e u r o s c i e n c e , 3,335-344.  46 Jonides, J. (1981). V o l u n t a r y v e r s u s a u t o m a t i c c o n t r o l o v e r the m i n d ' s eye's m o v e m e n t . In J. B. L o n g a n d A . D. B a d d e l e y (Eds.), A t t e n t i o n a n d P e r f o r m a n c e IX (pp. 187-203). H i l l s d a l e , N J : E r l b a u m . K l e i n , R. M , K i n g s t o n e , A . & Pontefract, A . (1992). O r i e n t i n g of v i s u a l attention. In K. R a y n e r (Ed.), E y e M o v e m e n t s a n d V i s u a l C o g n i t i o n : Scene P e r c e p t i o n a n d R e a d i n g . (pp. 46-63). N o r t h - H o l l a n d : Elsevier Science P u b l i s h e r s B. V . K l e i n , R. M , & Shore D. I. (2000). Relations a m o n g m o d e s of v i s u a l o r i e n t i n g (commentary), I n S. M o n s e l l a n d J. D r i v e r (Eds.) A t t e n t i o n a n d P e r f o r m a n c e X V I I I (pp. 195-209). C a m b r i d g e , M A : M I T Press M u l l e r , H . J, & Rabbitt, P. M . A . (1989). R e f l e x i v e a n d v o l u n t a r y o r i e n t i n g of v i s u a l attention: time course of a c t i v a t i o n a n d resistance to i n t e r r u p t i o n . Tournal of E x p e r i m e n t a l P s y c h o l o g y : H u m a n P e r c e p t i o n a n d P e r f o r m a n c e , 15, 315-330. P o s n e r , M . I. (1980). O r i e n t i n g of attention. Q u a r t e r l y Tournal of E x p e r i m e n t a l P s y c h o l o g y , 32, 3-25. Posner, M . I, & Rothbart, M . K. (2000). D e v e l o p i n g m e c h a n i s m s of self-regulation. D e v e l o p m e n t a n d P s y c h o p a t h o l o g y , 12,427-441. Posner, M . I. (2001). T h e d e v e l o p i n g h u m a n b r a i n . D e v e l o p m e n t a l Science, 4, 253387. Rothbart, M . K., Posner, M . I, & R o s i c k y , J. (1994). O r i e n t i n g i n n o r m a l a n d p a t h o l o g i c a l d e v e l o p m e n t . D e v e l o p m e n t a n d P s y c h o p a t h o l o g y , 6, 635-652. R e n s i n k , R. A . , (1995). V S c o p e 1.2.7, M i c r o P s y c h Software, V a n c o u v e r , B r i t i s h C o l u m b i a , C a n a d a , c o p y r i g h t 1991 - 1 9 9 5 . Ristic, J, Friesen, C . K, & K i n g s t o n e , A . (2002). A r e eyes special? It d e p e n d s o n h o w y o u l o o k at it. P s y c h o n o m i c B u l l e t i n a n d R e v i e w , 9,507-513. V a l e n z a , E, S i m i o n , F, & U m i l t a , C . (1994). I n h i b i t i o n of r e t u r n i n n e w b o r n infants. Infant B e h a v i o r & D e v e l o p m e n t , 17, 293-302.  

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