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UBC Theses and Dissertations

The effects of auditory distraction on visual attention Lyttleton, Hugh Attrill 1948

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££3 /37 S3 The E f f e c t s o f A u d i t o r y D i s t r a c t i o n on V i s u a l A t t e n t i o n A T h e s i s Submitted i n P a r t i a l F u l f i l m e n t o f the Requirements f o r the Degree o f ' MASTER OF ARTS i n the Department o f PHILOSOPHY AND PSYCHOLOGY Hugh A t t r i l l L y t t l e t o n THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1948. A b s t r a c t o f THE EFFECTS OF AUDITORY DISTRACTION ON VISUAL ATTENTION. The present experiment was conducted to d i s c o v e r i f , w i t h i n p r e s c r i b e d l i m i t s , the Woodworth and W e l l s Num-bers C a n c e l l a t i o n Test would measure d i s t r a c t i o n e f f e c t s , age d i f f e r e n c e s and sex d i f f e r e n c e s . The procedure i n v o l v e d the a d m i n i s t r a t i o n o f the t e s t to f o u r age groups o f sub j e o t s . These age groups were nine, twelve, f i f t e e n and e i g h t e e n - y e a r - o l d s . The s u b j e c t s were s e l e c t e d from p u b l i c s c h o o l s and j u n i o r and senior h i g h schools i n the Vanoouver area. The t o t a l number o f su b j e c t s Involved was 361 grouped as f o l l o w s : n i n e - y e a r -o l d s — 85, t w e l v e - y e a r - o l d s — 8 6 , f i f t e e n - y e a r - o l d s — 9 5 , and e i g h t e e n - y e a r - o l d s — 9 5 . The s u b j e c t s , t e s t e d i n s m a l l groups, were g i v e n a p r a c t i c e t r i a l , immediately f o l l o w e d by a t r i a l w i t h t r a f f i c sounds and then a t r i a l w ith music sounds, and f i n a l l y , a t r i a l i n s i l e n c e . T h i s l a s t t r i a l was used as the c o n t r o l . A d i f f e r e n t numeral t o be can-c e l l e d was used f o r each t r i a l and these designated numer-a l s were r o t a t e d f o r the sub-groups w i t h i n each age group. The use o f d i f f e r e n t numerals and t h e i r r o t a t i o n was made to e l i m i n a t e p r a c t i c e e f f e c t s and p o s i t i o n a l h a b i t s as f a r as p o s s i b l e . The a n a l y s i s o f the data r e v e a l e d age and sex - 2 -d i f f e r e n c e s while no d i s t r a c t i o n e f f e c t s were apparent. F a o t o r s a f f e c t i n g the r e s u l t s may have been weakness o f the d i s t r a c t i n g s t i m u l i , h a b i t u a t i o n o f the a i s t r a c t o r s , i n c r e a s e d e f f o r t , o r p o s s i b l y the b r e v i t y o f the t e s t (two mi n u t e s ) . E a r l i e r m a t u r i t y o f hand-eye c o - o r d i n a t i o n and r e a c t i o n time i n g i r l s seems to account f o r t h e sex d i f f e r -ences found. Age d i f f e r e n c e s may be accounted f o r by g r e a t e r f a m i l i a r i t y with the m a t e r i a l and t e s t s i t u a t i o n s , and r e d u c t i o n i n r e a o t i o n time f o r the o l d e r s u b j e c t s . The f i n d i n g s o f t h i s experiment may be summarized as f o l l o w s : 1. The a u d i t o r y d i s t r a c t i o n s used had no s t a t i s t i c a l l y s i g n i f i c a n t e f f e c t s on the Woodworth and W e l l s Numbers C a n c e l l a t i o n T e s t . 8. Performance on the Woodworth and W e l l s Numbers C a n c e l l a -t i o n Test c o n s i s t e n t l y i n c r e a s e d w i t h age. 3 . The performance o f g i r l s on the Woodworth and W e l l s Numbers C a n c e l l a t i o n T e s t tended to be s u p e r i o r to t h a t o f boys. 4. The percentage e r r o r was i n v e r s e l y p r o p o r t i o n a l to age f o r boys and g i r l s on the Woodworth and We l l s Numbers C a n c e l l a t i o n T e s t . As a r e s u l t o f t h i s experiment a number o f prob-lems f o r f u r t h e r r e s e a r o h have been suggested. CONTENTS Chapter I Fundamental Concepts B e l a t e d to the Problem i n D i s t r a c t i o n . Page 1 Chapter IT A Conspectus o f P r e v i o u s Ex-periments i n A u d i t o r y D i s t r a c -t i o n . 8 Chapter I I I The T e s t , the S u b j e c t s , and the Procedure. 20 Chapter IV S t a t i s t i c a l A n a l y s i s o f Test Data. 27 Chapter V Co n c l u s i o n : an I n t e r p r e t a t i o n o f Test Data. 40 Summary 46 Appendix 48 B i b l i o g r a p h y 49 LIST OF TABLES Table I Table ' I I Tabl e I I I Table IV Table V Table VI Table VII Table V I I I Numerals C a n c e l l e d by Each S e c t i o n o f Each Age L e v e l During Each T r i a l . Average Age o f S u b j e c t s i n Each Age Group. Average I n t e l l i g e n c e Quotient o f S u b j e c t s i n Each Age Group. Mean, Standard D e v i a t i o n and Standard E r r o r o f the Mean f o r Each Experimental C o n d i t i o n by Age and Sex. S i g n i f i c a n c e o f the D i f f e r e n c e s between Mean Scor e s o f V a r i o u s Age Groups, Sexes Separate, f o r Each Experimental C o n d i t i o n . S i g n i f i c a n c e o f the D i f f e r e n c e s between Mean Scor e s f o r Each Experimental C o n d i t i o n by Age and Sex. S i g n i f i c a n c e o f the D i f f e r e n c e s between Mean Scores o f the Two Sexes at the Four Ages f o r Each Experimental C o n d i t i o n . Average E r r o r and Percentage E r r o r f o r Each Age L e v e l by Sex f o r Eaoh Experimental C o n d i t i o n . Page 24 27 28 SO 32 34 36 38 The E f f e c t s o f A u d i t o r y D i s t r a c t i o n on V i s u a l A t t e n t i o n CHAPTER I FUNDAMENTAL CONCEPTS RELATED TO THE PROBLEM IN DISTRACTION. D i s t r a c t i o n i s a phenomenon that may occur when-ever two o r more s t i m u l i appear i n temporal concomitance w i t h i n the environment o f the i n d i v i d u a l . These s t i m u l i may a c t i v a t e one o r more o f the sensory r e c e p t o r s . The , number o f p o s s i b l e combinations o f s t i m u l i t h a t may r e s u l t i n d i s t r a c t i o n i s l i m i t e d o n l y by the c a p a c i t y and number of the r e c e p t o r mechanisms. As a phenomenon o f c o n s i d e r a b l e complexity, d i s t r a c t i o n would seem to o f f e r a s i g n i f i c a n t f i e l d f o r p s y c h o l o g i c a l i n v e s t i g a t i o n . D i s t r a c t i o n becomes a problem when i t i n t e r f e r e s with a t t e n t i o n , that i s , when the a b i l i t y of the i n d i v i d u a l t o att e n d to a d e s i r e d stimu-l u s , or s e r i e s of s t i m u l i , i s impaired by the presence o f other s t i m u l i which have no connection with the objeot o f a t t e n t i o n . Because it. i m p a i r s the i n d i v i d u a l ' s a b i l i t y to att e n d , d i s t r a o t i o n is. a l s o a problem i n e f f i c i e n c y , o f response. As a problem i n v o l v i n g human e f f i c i e n c y , d i s t r a c -t i o n at once assumes great p r a c t i c a l importance. Any r e -search on t h i s s u b j e c t , t h e r e f o r e , has a twofold p u r p o s e — f i r s t , an understanding of the c o n d i t i o n s which produce d i s t r a c t i o n and second, the s o l u t i o n o f some of the prob-lems i n v o l v e d i n e f f i c i e n t response. - 2 -P r e l i m i n a r y t o any study o f the phenomenon o r problems of d i s t r a c t i o n , i t i s e s s e n t i a l to have an under- . stan d i n g of the fundamental concepts of d i s t r a c t i o n , a t t e n -t i o n and e f f i c i e n c y , as t h e y are i n v o l v e d i n the t o t a l pat-t e r n o f stim u l u s and response. The meaning o f these con-cepts and t h e i r r e l a t i o n s h i p to each o t h e r i s o f importance i n c o n s t r u c t i n g an experiment and i n e v a l u a t i n g the r e s u l t s obtained from conducting t h a t experiment. A d i s t r a c t o r , by d e f i n i t i o n ( 1 5 ) , i s that which d i v i d e s , confuses, d i v e r t s , o r draws away the a t t e n t i o n . Any s t i m u l u s which d i v e r t s the a t t e n t i o n from an o b j e c t and, consequently, becomes the new o b j e c t of a t t e n t i o n i s a d i s t r a c t o r . As-a s t i m u l u s i t i s no d i f f e r e n t from any ot h e r type o f stimulus to which the i n d i v i d u a l may respond. The determiners of a t t e n t i o n are a l s o the deter m i n e r s o f d i s t r a c t i o n . P o f f e n b e r g e r ( 3 4 ) i l l u m i n a t e s t h i s p o i n t v e r y c l e a r l y i n h i s d i s c u s s i o n . He shows that the d i s t i n c -t i o n made between d i s t r a c t o r s and' o b j e o t s of a t t e n t i o n i s u s u a l l y o f the u t i l i t a r i a n type, o n l y those o b j e c t s t h a t i n t e r f e r e with work being catalogued a s d i s t r a c t o r s . A c t u a l l y , any stimulus may be e i t h e r a d i s t r a c t o r or an obj e c t o f a t t e n t i o n , depending on the m o t i v a t i o n and d e s i r e s at the moment. A t t e n t i o n may be d e f i n e d as a c t i v i t y which r e s u l t s i n a v i v i d p e r c e p t i o n o f a g i v e n o b j e c t ( 4 5 ) . I t i s e x h i b i t e d by the d i r e c t i o n of the e n t i r e p e r c e p t u a l meohanism toward a ciroumsoribed area of the environment. Although t h i s a b i l i t y o f the organism to f o c u s i t s e l f upon an o b j e c t i s not understood completely, some data have been accumulated. The e n t i r e organism a p p a r e n t l y a d j u s t s I t s e l f f o r b e t t e r p e r c e p t i o n and p r e p a r e s f o r b e t t e r r e s -ponse to the s t i m u l i r e c e i v e d . T h i s adjustment extends to the muscles a s s o c i a t e d w i t h the sense organs, to the s k e l e t a l muscles, and to the v i s c e r a . F a c t o r s r e s p o n s i b l e f o r t h i s c o n c e n t r a t i o n are both e x t e r n a l and i n t e r n a l . The e x t e r n a l determiners of a t t e n t i o n i n c l u d e i n t e n s i t y , q u a l i t y 4 suddenness, c e s s a t i o n , motion, and. n o v e l t y . o f the stimulus. These determiners tend to a t t r a c t the a t t e n t i o n , but the i n t e r n a l determiners i n c l u d i n g f e e l i n g s , i n t e r e s t s , d e s i r e s and h a b i t s ( sometimes designated by the term apperception) are necessary to h o l d the a t t e n t i o n when once aroused. Warren and Carmichael .(44) p o i n t out that an i n d i v i d u a l i s always a t t e n d i n g when awake and t h a t a t t e n -t i o n s h i f t s r a p i d l y from p o i n t to p o i n t i n the environment. T h i s type o f a t t e n t i v e n e s s , however, i s l i t t l e more than • awareness. The type o f a t t e n t i o n under d i s c u s s i o n i s t h a t which i s c o n t r o l l e d o r d i r e o t e d , u s u a l l y f o r some con s i d e r a b l e d u r a t i o n . I t l s manifested not. o n l y i n the o r i e n t a t i o n o f the i n d i v i d u a l to the p a r t i o u l a r s t i m u l i , but a l s o i n the i n h i b i t i o n o f the • r e c e p t i o n of i r r e l e v a n t s t i m u l i i n those oases where o t h e r o b j e c t s tend to a t t r a c t the a t t e n t i o n away from i t s f o c u s . D i r e c t e d a t t e n t i o n produces c l e a r e r p e r c e p t i o n , but e v e n t u a l l y l e a d s to f a t i g u e o f both r e c e p t o r s and e f f e c t o r s , r e s u l t i n g i n f e e l i n g s of s t r a i n and weariness In the i n d i v i d u a l . The d e f i n i t i o n o f e f f i o i e n o y i n the p h y s i c a l s c i e n c e s i s a p p l i c a b l e i n the f i e l d o f psychology. E f f i -c i e n c y i s d e f i n e d as the r a t i o of output d i v i d e d by i n p u t . I t i s the r a t i o between work done o r accomplish-ment and energy consumption whether i n an I n d i v i d u a l or a machine. Accomplishment can be measured r e a d i l y i n terms o f uni°ts o f work. Energy consumption, however, can-not be measured so r e a d i l y because i t i s at p r e s e n t impos-s i b l e to know a l l the uses t o which the energy supply i s put i n f o c u s i n g the a t t e n t i o n . The degree of e f f o r t r e -q u i r e d i n a t t e n d i n g depends upon the e f f e c t i v e n e s s o f the i n t e r n a l and e x t e r n a l d eterminers of a t t e n t i o n . T h i s v a r i a t i o n n a t u r a l l y a f f e o t s the amount of energy consumed and, consequently, the e f f i c i e n c y o f the i n d i v i d u a l . I t may o r may not a f f e c t the output. A number o f observable p h y s i o l o g i c a l changes have been checked e x p e r i m e n t a l l y i n an attempt to show changes i n energy consumption. Measurements have been made o f p u l s e r a t e , b r e a t h i n g r a t e , t a c t u a l p r e s s u r e , and muscular t e n s i o n . These measurements may be i n d i c a t i v e , but have so f a r proven o f l i t t l e v a lue i n determining energy changes. At;.the present time, the use of such measures to show that e f f i c i e n c y i s or can be held constant is - not warranted. The r e s u l t s obtained.are a r t i f a c t s o f t h e experimental s i t u a t i o n or e l s e are based on the absence o f observable - 5 -ohanges i n the s u b j e c t . As yet t h e r e are no adequate data upon which to c o n s t r u c t a u s e f u l e f f i c i e n c y curve. The r e l a t i o n s h i p between the concepts o f d i s -t r a c t i o n , a t t e n t i o n and e f f i c i e n c y i s not immediately e v i d e n t . I t would appear t h a t v a r i a t i o n s i n any one would produce changes i n the other two. T h i s does not n e c e s s a r i l y h o l d t r u e . F o r example, a change i n the d i s -t r a c t i n g s t i m u l u s w i l l not a f f e c t the e f f i c i e n c y o f the i n d i v i d u a l u n l e s s that change causes a v a r i a t i o n i n the energy consumption r e q u i r e d to m a i n t a i n the degree o f a t t e n t i o n n e c e s s a r y f o r a g i v e n t a s k . As the a t t e n t i o n v a r i e s so does the e f f i c i e n c y . But the a t t e n t i o n cannot vary u n l e s s e i t h e r some d i s t r a c t i n g s t i m u l u s v a r i e s , or the e x t e r n a l determiners o f a t t e n t i o n l o s e t h e i r power. Wavering o f a t t e n t i o n might r e s u l t a l s o from s a t i a t i o n o f c u r i o s i t y or d e s i r e or i n a b i l i t y to comprehend the stimu-l u s s i t u a t i o n . In c o n t r a s t to t h i s s i t u a t i o n , a s t i m u l u s may appear t h a t i s stronger than the one.on which the a t t e n t i o n i s focused. Any s t i m u l u s might c o n c e i v a b l y pro-duce t h i s r e s u l t . It appears then t h a t v a r i a t i o n i n e i t h e r the d i s t r a c t i o n p a t t e r n o r the a t t e n t i o n s t i m u l u s p a t t e r n i n f l u e n c e s the e f f i c i e n c y o f the i n d i v i d u a l and i s f i n a l l y m anifested i n the form o f output. It i s important to n o t i c e . t h a t t h i s sequence i s not r e v e r s i b l e at any p o i n t . The experimental approach to the s u b j e c t o f d i s t r a c t i o n i s c o n t r o l l e d by the comprehensiveness o f the problem to* be s t u d i e d . U s u a l l y , the o b j e c t o f a t t e n t i o n i s a r e l a t i v e l y simple a o t i v i t y demanding continuous con-c e n t r a t i o n f o r r a p i d and accurate performance o f a t a s k . The d i s t r a c t o r may c o n s i s t o f any type o f s t i m u l u s appear-in g i n the same sensory mode as the o b j e c t of a t t e n t i o n or i n any other mode. A s i n g l e repeated s t i m u l u s i s customary, although some experimenters have combined s e v e r a l s t i m u l i appearing i n d i f f e r e n t sensory modes. A disadvantage o f t h i s l a t t e r method i s that i t i s impossi-ble to determine which o f the combination of d i s t r a c t o r s i s having the g r e a t e s t e f f e c t . The accepted method o f determining the e f f e c t s o f a d i s t r a c t i o n on a subject, o r a .group o f s u b j e c t s , is. t o present the d i s t r a c t o r and the o b j e c t o f a t t e n t i o n t o g e t h e r . The performance under these c o n d i t i o n s i s then compared wi t h the performance made when the o b j e c t o f a t t e n t i o n i s presented a l o n e . Any d i f f e r e n c e between these two performances i s considered t o i n d i c a t e the e f f e c t i v e n e s s o f the d i s t r a c t i n g s t i m u l i . In the present study o f the e f f e c t s o f d i s t r a c t i o n the a t t e n t i o n i s a t t r a c t e d toward the v i s u a l f i e l d , while the d i s t r a c t i n g s t i m u l i appear i n the a u d i t o r y sense mode. Two s e r i e s o f c o n f l i c t i n g s t i m u l i , one a u d i t o r y and one v i s u a l , tend to determine the d i r e c t i o n o f the a t t e n t i o n of the i n d i v i d u a l . The v i s u a l s e r i e s i s the predetermined objeot o f a t t e n t i o n while the a u d i t o r y s e r i e s i s the d i s t r a c t o r . The o b j e c t o f a t t e n t i o n i s i n the form o f a speed t e s t t h a t can be scored to show, the work accomplished by the i n d i v i d u a l . The d i s t r a c t o r i s composed of meaning-- 7 -f u l and nonsense m a t e r i a l . The experiment i s based on the a b i l i t y o f the subject to n e g o t i a t e , w i t h i n a g i v e n time l i m i t , as much as p o s s i b l e o f the Woodworth and W e l l s Numbers C a n c e l l a t i o n Test d u r i n g p e r i o d s of s i l e n c e and a u d i t o r y s t i m u l a t i o n . The purpose of the i n v e s t i g a t i o n i s t h r e e f o l d . F i r s t , t o d i s c o v e r i f the t e s t , w i t h i n the l i m i t s o f the experiment, w i l l measure the e f f e c t s of d i s t r a c t i o n . Second, to determine i f the t e s t r e s u l t s w i l l show sex d i f f e r e n c e s . T h i r d , to determine age d i f f e r e n c e s i n . a b i l i t y to o a n c e l d i g i t s . The experiment was conducted i n such a manner that the data f o r the three problems were c o l l e c t e d d u r i n g one t e s t p e r i o d f o r each group o f s u b j e c t s . T h i s pro-cedure tended to hold the experimental c o n d i t i o n s constant. CHAPTER I I A CONSPECTUS OP PREVIOUS EXPERIMENTS IN AUDITORY DISTRACTION. Mental work i s performed i n an environment f u l l o f s t i m u l i extraneous to the ta s k at hand. The e f f e c t t h a t these s t i m u l i have i n d i v e r t i n g the a t t e n t i o n from the work being undertaken r e s u l t s i n the phenomenon and problem o f d i s t r a c t i o n . T h i s e f f e c t v a r i e s w i t h i n d i v i d -u a l s , time, p l a c e and the type o f work being done. What may be a d i s t r a c t i n g s timulus i n one s i t u a t i o n may become a f a c i l i t a t i n g s t i m u l u s i n a d i f f e r e n t s i t u a t i o n . T h i s v a r i a t i o n may be i l l u s t r a t e d by the example of music as a stimulus. By i t s rhythm!o nature, music may improve the performance o f a c e r t a i n type o f work, w h i l e i n o t h e r i n s t a n o e s i t may have e i t h e r no e f f e c t or a d e t r i m e n t a l e f f e c t ( 4 5 ) . T h i s range o f e f f e c t s may be observed a l s o as a r e s u l t o f rhythmic s t i m u l i o t h e r than music. Such s t i m u l i may o r may not have a rhythm s i m i l a r to that i n v o l v e d i n the s p e c i f i c type of work b e i n g performed. S t i m u l i which are f a c i l i t a t i v e are not t r u e d i s t r a c t i o n s because they do not decrease e f f i c i e n c y by d i v e r s i o n o f the a t t e n t i o n . Only when the s t i m u l u s produces a lessened e f f i c i e n c y can i t be c a l l e d a d i s t r a c t i o n . The b a s i c equipment and procedures o f a d i s t r a c -t i o n experiment are simple. While a p r e s c r i b e d task i s being performed, extraneous s t i m u l i are i n t r o d u c e d i n t o - 9 -the situation. The subject may or may not know that the stimuli are to be presented. He may be told to ignore them, or he may be told nothing about them other than that they are to be presented. The stimuli must be of a type that w i l l not mask the work being done ( 4 5 ) . For example, i f the work involves visual stimuli the distrac-tors must not involve blinding lights that w i l l impair the subject's a b i l i t y to see the work in front of him. As Woodworth (45) points out, in experimental situations when the task involves the use of one sensory mode the distracting stimuli appear usually in another mode. This i s particularly true of work done in the visual-sensory mode ( 3 4 ) . The type of task set for the subjects may be either of a simple nature or very complex. A number of experimenters have used intelligence tests, reading material, typing exercises and maze tracing. Others have used the work provided in the industrial situation. As a rule, the early investigators made use of simple reaction experiments, such as pressing a key on receiving a visual or auditory cue. The distraoting stimuli presented have consisted of music, monologue., lights, bells, buzzers, and street noises. The greater part of the work has been done with school children and oollege students, while some studies have been done with factory employees. The methods, with variations in procedure, involve a compari-son of results obtained by testing with and without - 10 -d i s t r a o t i n g stimuli. In the majority of studies reported, the object of attention has been i n the v i s u a l sensory mode and the d i s t r a c t i n g stimuli have been i n the auditory sense mode. Some work has been done, however, i n which the two series of stimuli have been i n the same sense mode. Casse.l and Dallenbach's (8) study involved the presentation of extraneous auditory stimuli to the subjects l i s t e n i n g for a s p e c i f i c sound stimulus. Hovey (£2) used a spotlight and stunt men as v i s u a l d i s t r a c t o r s while h i s subjects were working on an i n t e l l i g e n c e t e s t . Ruggles (3) also has devised a test of d i s t r a c t a b i l i t y . This i s measured by noting the d i s t r a c t i o n e f f e c t o f a number of irrelevant pictures looated on the borders of the test paper. To study the e f f e c t s of auditory d i s t r a c t i o n on v i s u a l attention, experimenters have used situations varying from simple stylus mazes to oomplex i n t e l l i g e n c e t e s t s . In one of Tinker's (41) experiments, h i s t h i r t y -nine subjects were required to negotiate aamaze by means of a stylus conneoted with an e l e c t r i c b e l l . Contacts of the stylus with the sides of the pathway rang the b e l l . Tinker considered this: procedure to involve audi-tory d i s t r a c t i o n . It would appear, however, that the sound of the b e l l i s not a true d i s t r a c t i o n , but rather o f f e r s a type of guidance i n which the subject i s informed of h i s errors. Jensen (26) administered typing exercises accompanied by music to f i f t y subjects i n h i s experimental - 11 -work on d i s t r a c t i o n . I t i s p o s s i b l e that t h i s approach has some m e r i t , although the noise of the t y p e w r i t e r s i n a c t i o n may c o n d i t i o n the s u b j e c t s to a considerable volume of sound o f a c e r t a i n type. Morgan (45) used a code s u b s t i t u t i o n t e s t as the task i n h i s study. This t e s t . was administered i n the presence of a number o f b e l l s and buzzers. Jenkins (25) used a pegboard t r a n s f e r t e s t i n the presence of constant s t i m u l a t i o n of a sound of 260 cyoles. This type o f t e s t would appear to be d i f f i -c u l t , i f not impossible, to administer to groups of sub-j e c t s as planned f o r the present experiment. Cas s e l and Dallenbach (8) required t h e i r subjects to r e l e a s e a de-pressed t e l e g r a p h key on hearing a Wundt sound hammer. A v a r i e t y o f a u d i t o r y s t i m u l i was used as d i s t r a c t o r s . In t h i s i n v e s t i g a t i o n the a t t e n t i o n o f the subject i s d i -vided between keeping the t e l e g r a p h key depressed and l i s t e n i n g f o r an a u d i t o r y stimulus. I t would appear that any d i s t r a c t i n g s t i m u l i present would be i n e f f e c t i v e due to the strength of the conditioned response b u i l t up i n the s u b j e c t s . Ford (14) and S c h n e l l (38) presented mathematical problems to t h e i r subjects during the c o n t r o l and experimental s i t u a t i o n s . Fendrick (13) presented a selected piece, o f r e a d i n g m a t e r i a l , aooompanied by-music, to h i s subjects. This was followed by a s e r i e s o f questions to determine the amount of Information the subjects had obtained from t h e i r reading. Various - 12 -i n t e l l i g e n c e t e s t s were used by T i n k e r (42), Hovey (22), and Brown (4) as the o b j e c t o f a t t e n t i o n i n t h e i r experiments. K e r r (27) had 228 r a d i o tube workers and e l e c t r i c a l equipment assemblers f i l l out a q u e s t i o n n a i r e r e g a r d i n g t h e i r p r e f e r e n c e f o r working i n the presence o f music o r i n the absence o f a u d i t o r y s t i m u l i . He found a decided d e s i r e f o r frequent b r o a d c a s t s o f music d u r i n g the working p e r i o d . C a n c e l l a t i o n and a d d i t i o n t e s t s were used by Obata, M o r i t a , H i r o s e and Matsumoto ( 3 3 ) . T h e i r c a n c e l l a t i o n t e s t , composed o f Japanese symbols, was administered i n the presence o f music and n o i s e to t h i r t y - t w o subjeots, twenty-four of whom were school c h i l d r e n . The c a n c e l l a t i o n t e s t technique has t h e advantages o f being extremely simple, o f being r e a d i l y understood, and o f r e q u i r i n g a h i g h degree o f a t t e n t i o n and hand-eye c o - o r d i n a t i o n . I t can be administered to a l a r g e group o f s u b j e c t s without referenoe to age or sex. Furthermore, the t e s t m a t e r i a l can be q u i c k l y scored. One o f the best examples o f t h i s type o f t e s t a v a i l a b l e i n t h i s country i s the Wood-worth and Wells Numbers Cancel-l a t i o n T e s t ( 46). The d i s t r a c t o r s that have been used i n these i n v e s t i g a t i o n s vary from simple m u s i c a l tones to extremely complex sound p a t t e r n s . Jenkins (25) used a continuous, tone o f 260 c y c l e s as h i s o n l y d i s t r a c t i n g s t imulus. - 13 -T h i s type o f stimulus has the disadvantage t h a t a mono-tonous tone may become r e a d i l y h a b i t u a t e d ( a s J e n k i n s p o i n t e d o u t ) , because i t u s u a l l y does not o f f e r s u f f i c i e n t v a r i a t i o n o f q u a l i t y or i n t e n s i t y to continue to h o l d the a t t e n t i o n o f the s u b j e c t s a f t e r i t s f i r s t appearance. I t may have the o p p o s i t e e f f e c t , however, as S c h n e l l (38) d i s c o v e r e d , and c o n t r i b u t e to i n c r e a s i n g the output o f the s u b j e c t s . T i n k e r (41), (42), i n both o f h i s experiments, used an e l e c t r i c b e l l as the d i s t r a c t i n g s t i m u l u s . In the f i r s t o f these experiments the b e l l was sounded every time h i s s u b j e o t s cohtaoted e i t h e r side o f a maze w i t h a t r a c i n g s t y l u s . In the second experiment the b e l l was rung, i n t e r m i t t e n t l y by the i n v e s t i g a t o r w h i l e the sub-j e c t s were n e g o t i a t i n g an i n t e l l i g e n c e t e s t . Musio was used as the d i s t r a c t o r by Jensen (26), F e n d r i c k (13) and Obata, M o r i t a , H i r o s e and Matsumoto ( 3 3 ) . Jensen p l a y e d a l t e r n a t e s e l e c t i o n s o f d i r g e and j a z z music to t h r e e groups o f s u b j e c t s doing t y p i n g e x e r c i s e s . The r e s u l t s o btained were oompared wi t h a second set o f r e s u l t s taken from the same groups r e p e a t i n g the work under normal c o n d i t i o n s . F e n d r i c k presented music to a group o f students who were r e q u i r e d to read a prose s e l e c t i o n . A f t e r the r e a d i n g p e r i o d he questioned the students. He then compared the answers w i t h answers g i v e n to the same q u e s t i o n s by a c o n t r o l group. He found that h i s - 14 -o o n t r o l group d i d c o n s i s t e n t l y b e t t e r work than d i d the experimental group. Obata, M o r i t a , H i r o s e and Matsumoto (33) presented music to t h e i r s u b j e c t s while they were perfo r m i n g c a n c e l l a t i o n and a d d i t i o n t e s t s . The r e s u l t s obtained were oompared with those o f the same group working under normal c o n d i t i o n s . Humes (23) i n v e s t i g a t e d the e f f e o t s o f music on the output of e i g h t y - e i g h t women r a d i o tube assemblers. During each hour o f the normal work day i n an i n d u s t r i a l s i t u a t i o n , music was played f o r t e n minutes. F a s t tempo music was used d u r i n g the f i r s t three-week p e r i o d , f o l -lowed by th r e e weeks of slow tempo music. D u r i n g a t h i r d p e r i o d o f t h r e e weeks, s e l e c t e d p i e c e s o f slow and f a s t tempo music were used. T h i s was f o l l o w e d by a two-week p e r i o d without musio. The output o f the workers was compared with t h e i r average output f o r the f i v e weeks immediately p r e c e d i n g the i n v e s t i g a t i o n , d u r i n g which random s e l e c t i o n s o f music had been broadcast. He found that t h e r e was l e s s scrappage o f tubes assembled d u r i n g p e r i o d s when e i t h e r a l l f a s t music or a l l slow music was played than d u r i n g any o t h e r p e r i o d . He b e l i e v e s t h i s improvement i s not e n t i r e l y due to the music, although no o t h e r f a c t o r s are observable. C a s s e l and Dall e n b a c h (8) used s e p a r a t e l y a metronome, a b e l l and a t u n i n g f o r k a s the d i s t r a c t i n g ' s t i m u l i i n t h e i r experiment. Each o f these s t i m u l i was - 15 -presented during a series of ten reactions of the subjects to'the Wundt sound hammer. The r e s u l t s obtained under these conditions were oompared with similar s e r i e s per-formed i n silence. These auditory stimuli may be ade-quate for research with i n d i v i d u a l subjects under laboratory conditions but, where subjects are to be tested i n groups, d i s t r a c t o r s with considerable i n t e n s i t y or volume are imperative. The most elaborate group of situations was used by Hovey (22). While 173 o f h i s 294 subjects were working on the Army Alpha Intelligence Test Form 7, he introduced as d i s t r a o t i n g stimuli a number of b e l l s and buzzers, a spotlight, organ pipes, whistles, a camera, a c i r c u l a r saw, a rotary spark gap, and four stunt men. These devices were used singly and i n groups during the experiment. The r e s u l t s obtained on the i n t e l l i g e n c e test were compared with those of the control group. Distractors that appear to be suitable f o r the present investigation are of the type used by Ford (14), Schnell (38), and Gason (6). Ford used an automobile horn and a recording of a supposedly humorous monologue. The monologue i s quite appropriate i n that i t i s possible to have a group of people working i n the presence of con-versation. . Schnell used monotonous sounds and street noises as d i s t r a o t o r s i n h i s experiment. Cason provided h i s subjects with t y p i c a l classroom d i s t r a c t i o n s , while - 16 -they were working on normal classroom projects, such as mathematical problems and reading material. From purely practical considerations, the stimuli to be presented in an experiment on distraction should be typical of that situation in which they appear normally. It does not seem useful to l i f t a number of different stimuli, or series of stimuli, from a pattern and to present them as a unit in an experimental situation where they have no relation to. each other or to the object of attention. It follows that the entire experiment should be a unified and coherent structure in which each part appears in logical relation to the other parts, resulting in a representative sample of a conceivable situation. The method of testing also must be appropriate to the task set for the subjects. The two outstanding methods that have been used are the group tests conducted in the classroom, and the individual tests administered in a laboratory. The greater part of the re*searoh has been done with groups of subjects in.the classroom situation. The investigators using this method include Tinker (4E), Hovey (22), Ford (14), Jensen (26), Schnell (38), Fendriok (13), Cason (6) and Obata, Morlta, Hlrose and Matsumoto (33). In contrast to the method of group test-ing i s the method of individual testing conducted in the laboratory, the method used by Gassel and Dallenbach (8), Morgan ( 45) and Tinker ( 41). - 17 -In order to compare the r e s u l t s obtained during d i s t r a c t i o n w i t h the r e s u l t s obtained during q u i e t , one of two procedures must be used. E i t h e r the same group of subjects must be used twice under d i f f e r e n t c o n d i t i o n s , or two groups, an experimental group and a c o n t r o l group, must be used. The f i r s t method r e q u i r e s the e l i m i n a t i o n of, o r the allowance f o r , a l l p r a c t i c e e f f e c t s i n order t h a t the r e s u l t s w i l l be v a l i d . The second method In-vol v e s the equating of the two groups i n order t h a t r e l i a b l e comparisons may be made. The f i r s t method was used by Cassel and Dallenbach ( 8 ) , T i n k e r (41), Jenkins (25), Jensen (26), Humes (23) and Obata, M o r i t a , Hirose and Matsumoto (33). The second method was used by Tinker (42), Hovey (22) and Fendrick (13). These experiments show no u n i f o r m i t y o f r e s u l t s . Cassel and Dallenbach (8) found no con s i s t e n t d i s t r a c t i o n e f f e c t s apparent i n t h e i r work. While i n some cases they found i n c r e a s e s i n r e a c t i o n time, i n d i c a t i n g d i s t r a c t i o n , they a l s o found i n other oases decreases i n r e a c t i o n time under the same c o n d i t i o n s . Tinker (41) found, as might be t expected, improved s t y l u s maze performance due to the guidance e f f e c t o f h i s a l l e g e d d i s t r a c t i o n stimulus. As a r e s u l t o f h i s second experiment, i n which a b e l l was sounded during i n t e l l i g e n c e t e s t i n g , T i n k e r (42) again found no r e l i a b l e evidenoe o f d i s t r a c t i o n . Hovey (22), however, studying i n t e l l i g e n c e t e s t performance i n the - 18 -presence o f a great v a r i e t y of d i s t r a c t i o n s , i n t e r p r e t e d h i s r e s u l t s as i n d i c a t i n g improved performance when.com-pared w i t h the r e s u l t s obtained d u r i n g q u i e t p e r i o d s . Ford (14) ooncluded, as a r e s u l t o f h i s experimental . work, t h a t d i s t r a c t i o n i n i t i a l l y i n c r e a s e d the r e a c t i o n time and the number o f e r r o r s made. T h i s i n c r e a s e d i s -appeared w i t h i n the f i r s t h a l f o f each t e s t , but r e -appeared a t the b e g i n n i n g o f the f o l l o w i n g q u i e t p e r i o d . Ford does not c o n s i d e r what, r e s u l t s might have been obtained I f the order of p r e s e n t a t i o n had been r e v e r s e d . I t i s p o s s i b l e t h a t the c o n d i t i o n he mentions was due to an i n i t i a l warming up to the task, r a t h e r than, t o d i s -t r a c t i o n e f f e c t s . Jensen (26) found that t y p i n g i n the presence o f j a z z musio i n c r e a s e d the speed o f t y p i n g and the number o f e r r o r s i n comparison with t y p i n g i n q u i e t surroundings. Dirge music reduced the output but d i d not. a f f e c t the r e l a t i v e number o f e r r o r s . Jenkins (25) found no d i s -t r a c t i o n e f f e c t s and conoluded t h a t continuous tones are r e a d i l y h a b i t u a t e d . S c h n e l l (38), however, found that monotonous nois e had a s t i m u l a t i n g e f f e c t , w h i l e s t r e e t n o i s e s reduced the output. The r e s u l t s of the i n v e s t i g a -t i o n s o f Obata, M o r i t a , H i r o s e and Matsumoto (33) l e d these experimenters to conclude t h a t both musio and n o i s e a d v e r s e l y a f f e c t the working speed o f the su b j e o t s . P o s s i b l y the major f a c t o r p r o d u c i n g these ^ 19 -v a r i a t i o n s i n o o n c l u s i o n s i s the a b i l i t y o f the s u b j e c t s to cope with the d i s t r a c t i n g s t i m u l i . The subject may i n c r e a s e h i s e f f o r t to overcome the d i s t r a c t i o n and, as a r e s u l t , m a i n t a i n h i s output or even i n c r e a s e i t . Poffenberger (34) r e f e r s t o ' t h i s as the a b i l i t y to a d j u s t one's behaviour t o the complexity o f the t a s k . C e r t a i n s u b j e c t s , however, are unable to i n h i b i t com-p l e t e l y extraneous s t i m u l i without i m p a i r i n g t h e i r out-put. Another determinant i s the f a c t t h a t the d i s t r a o t -i n g s t i m u l i and the o b j e c t o f a t t e n t i o n , i n a number o f the s t u d i e s , are not i n the same sensory mode. Morgan (45) p o i n t s out that the most d i s t u r b i n g s t i m u l i are those t h a t a f f e c t the sense organs i n v o l v e d i n the t a s k . He p o i n t s out a l s o that meaningful m a t e r i a l i s more e f f e o t i v e as a d i s t r a c t o r than nonsense m a t e r i a l . CHAPTER I I I THE TEST, THE SUBJECTS, AND THE PROCEDURE. The Woodworth and W e l l s Numbers C a n c e l l a t i o n Test used as the o b j e c t o f a t t e n t i o n i n t h i s experiment o o n s i s t s o f twenty l i n e s o f A r a b i c numerals. The numbers are arranged i n groups o f f i f t y to a l i n e , with each o f the t e n d i g i t s i n the s e r i e s a p p e a r i n g f i v e times i n every l i n e . A l l numbers, consequently, appear one hundred times throughout the t e s t . They are arranged so t h a t no number appears twice i n s u c c e s s i o n anywhere i n the t e s t . The l a s t t e n l i n e s o f t h i s t e s t are the same as the f i r s t ten, except that the order o f the d i g i t s i s r e v e r s e d , thus making two h a l v e s o f the t e s t comparable i n d i f f i -c u l t y . The blank i s shown i n Appendix 1. Prom t h e i r own experimental work, Woodworth and Wells (46) concluded that t h i s t e s t was u s e f u l i n measuring f l u c t u a t i o n s i n a t t e n t i o n d u r i n g continuous work. Although they d i d not use the t e s t as the b a s i s o f a d i s t r a c t i o n experiment, these i n v e s t i g a t o r s p o i n t e d out that the Numbers C a n c e l l a t i o n Test might be used i n s t u d i e s o f i n t e r f e r e n c e . F o r the purposes o f the present i n v e s t i g a t i o n , the Woodworth and W e l l s T e s t was converted i n t o a time-l i m i t t e s t by the use o f a two-minute l i m i t . By so l i m i t i n g the time, i t was p o s s i b l e to a d m i n i s t e r the - 21 -t e s t to groups of s u b j e c t s . The s u b j e c t s were r e q u i r e d to draw a l i n e beside the numeral they were f i x a t i n g when a w h i s t l e sounded. The w h i s t l e was blown at the end o f each t h i r t y - s e c o n d i n t e r v a l . The s u b j e c t s were r e q u i r e d to c a n c e l each o f the d i g i t s 1, 2, 3, and 5 on separate t e s t b lanks. The l a s t t h ree o f these d i g i t s were chosen because they presented v i s u a l l y s i m i l a r p a t t e r n s , and because they are a p p r o x i -mately at the centre o f the s e r i e s o f d i g i t s arranged i n order o f d i f f i c u l t y o f c a n c e l l i n g . Woodworth and W e l l s (46) r e p o r t e d that the order o f i n c r e a s i n g d i f f i c u l t y i n c a n c e l l i n g the numbers was 1,7,0,4,2,3,5,8,6,9. The present experiment r e q u i r e d three d i f f e r e n t numbers i n order to t r y t o avoid p o s i t i o n a l h a b i t s and p r a c t i c e e f f e c t s i n the s u b j e c t s that might i n f l u e n c e the r e s u l t s i n the three experimental s i t u a t i o n s . It may be noted that f o r c e r t a i n c o n c l u s i o n s made i n t h i s experiment i t i s n e c e s s a r y t o assume that the t h r e e numerals used are. o f equal d i f f i c u l t y f o r the s u b j e c t s to c a n c e l . The present experiment i n v o l v e d the a d m i n i s t r a -t i o n o f the c a n c e l l a t i o n t e s t to 361 students o f elemen-t a r y s chools and o f j u n i o r and s e n i o r h i g h s c h o o l s . The two determining f a c t o r s c o n s i d e r e d i n the s e l e c t i o n o f the s u b j e c t s were age and sex. One hundred and n i n e t y -one male s u b j e c t s and one hundred and seventy female s u b j e c t s w i t h i n the d e s i r e d age range were obtained. The age c o n t r o l c o n s i s t e d o f s e l e c t i n g one group o f - 22 -s u b j e c t s at each o f f o u r age l e v e l s , 9, 12, 15, and 18 y e a r s . The g r e a t e s t v a r i a t i o n allowed at each l e v e l was three months above or below the s e l e c t e d age. I n t e l l i -gence q u o t i e n t and race were not s e l e c t i v e f a c t o r s , although the mental r a t i n g o f each s u b j e c t , on the b a s i s , of e i t h e r the N a t i o n a l I n t e l l i g e n c e Test o r the D e t r o i t I n t e l l i g e n c e Test, was obtained, wherever p o s s i b l e , from the f i l e s o f the Bureau o f Measurement o f the Vancouver School Board. The s u b j e c t s were s e l e c t e d from seven d i f f e r -ent s c h o o l s i n the Vancouver a r e a . From the K i t s i l a n o J u n i o r arid S e n i o r High Schools a l l the 15-year-olds and two s e c t i o n s o f the 18-year-olds.were ob t a i n e d . The remainder o f the 18-year-old s u b j e c t s came from Magee High School. The 12-year-old group was oomposed o f sec-t i o n s from l o r d K i t c h e n e r , Lord. Tennyson and H a s t i n g s Schools, w h i l e the n i n e - y e a r - o l d s were obtained at the Bayview, Queen Mary and Lord Tennyson Scho o l s . With the e x c e p t i o n o f the 15-year age l e v e l , i t was found impos-s i b l e to o b t a i n the d e s i r e d number o f s u b j e c t s in any one s c h o o l . T h i s was thought to be an advantage since i t p o s s i b l y ensured a more r e p r e s e n t a t i v e sampling o f the p o p u l a t i o n . - 83 -The equipment used f o r t h i s experiment c o n s i s -ted o f a small p o r t a b l e r a d i o w i t h a V i c t o r r e c o r d p l a y e r connected to the loudspeaker. Two r e c o r d s were used, a S i l v e r Masque t r a f f i c sound r e c o r d , No. M501A, and the V i c t o r r e c o r d i n g o f the " S t e i n Song" No. 180893A. The t r a f f i c noise r e c o r d was s e l e c t e d because o f i t s great i r r e g u l a r i t i e s i n i n t e n s i t y and q u a l i t y . The music r e c o r d was chosen f o r i t s marked rhythm and l a c k o f v o c a l r e f r a i n . F u r t h e r , i t was assumed that the musio would be known to a l l the s u b j e c t s and consequently have no emotional e f f e c t s . In answer to q u e s t i o n i n g , however, no subject was found who was able to name the composi-t i o n , although some recog n i z e d the tune. The s i g n a l w h i s t l e employed was o f the p e n e t r a t i n g v i b r a t i n g type used by o f f i c i a l s at s p o r t s events. A w r i s t watch with a sweep second hand was the t i m i n g d e v i c e . The volume was not c o n t r o l l e d but was such t h a t the sound could be heard d i s t i n c t l y i n any p a r t o f the room. In f a o t , the i n t e n s i t y was so great that a person speaking i n a normal v o i c e could not be heard at the back o f the room while the r e c o r d s were being p l a y e d . The w h i s t l e , blown to i n d i c a t e q u a r t e r , h a l f , and t h r e e -q u a r t e r time, was sounded w i t h a short s h r i l l b l a s t . Whenever the r e c o r d s were used, the s i g n a l to stop work was g i v e n concomitantly w i t h the s t o p p i n g o f the r e c o r d . The i n s t r u c t i o n s were read to the s u b j e c t s at - 24 -the be g i n n i n g o f each t e s t and i n c l u d e d blackboard demon-s t r a t i o n s o f the c a n c e l l a t i o n procedure. These proced-u r e s were f o l l o w e d w i t h a l l groups to hold m o t i v a t i o n as constant a s p o s s i b l e . U n i f o r m i t y o f procedure was impera-t i v e as i t was impossible to t e s t a l l the s u b j e c t s at one time or i n one p l a c e . Each age group was d i v i d e d i n t o t h r e e s e c t i o n s , designated A, B, and C, i n order t o g a i n f u r t h e r c o n t r o l i n the t e s t i n g . TABLE I NUMERALS CANCELLED BY EACH SECTION OF EACH AGE LEVEL DURING EACH TRIAL. S e c t i o n P r a c t i c e t r i a l T r i a l with t r a f f i c sounds T r i a l w i t h music T r i a l dur i n g s i l e n c e A 1 2 3 5 B 1 3 5 2 C 1 5 2 3 Fo r the f i r s t t r i a l the f o l l o w i n g i n s t r u c t i o n s were used. D i r e c t i o n s f o r D i s t r a c t i o n Test "I have a t e s t I want you to do. It i s very easy and you w i l l not have any t r o u b l e doing i t . T h i s - 25 -t e s t i s made up o f 20 l i n e s o f numbers. There are f i v e numbers that are the same i n eaoh l i n e . (Experimenter demonstrates by means o f the blackboard.) LISTEN CARE-FULLY. What I want you to do i s to c r o s s out a l l the l ' s WHEN I gi v e the s i g n a l . ( A g a i n experimenter demon-s t r a t e s . ) Each time you hear the w h i s t l e , draw a l i n e beside the number you are l o o k i n g at and go on working. (Experimenter demonstrates.) When I say "STOP" draw a l i n e b e side the number you have reached and l i f t your p e n c i l s up. LISTEN. When I say 'READY1 t u r n your papers over, when I say 'GO' begin c r o s s i n g out the l ' s . Cross out a l l the l ' s you can f i n d . Make the marks at the s i g n a l s and when I say 'STOP'. PENCILS UP, READY, GO. (Experimenter blows the w h i s t l e at the proper times.) STOP." For the second, t h i r d and f o u r t h t r i a l s the d i r e c t i o n s were m o d i f i e d . . In each o f these cases, a f t e r new blanks had been d i s t r i b u t e d and the s u b j e c t s had w r i t t e n t h e i r names i n the a p p r o p r i a t e space, the f o l l o w i n g i n s t r u c t i o n s were read. " T h i s time I want you to c r o s s out a l l the 2's when I give the s i g n a l . We w i l l do i t e x a c t l y the same as the l a s t time u s i n g the same s i g n a l s . There are f i v e o f each number to a l i n e . Hold your p e n c i l s up. PENCILS UP, READY, GO. (Experimenter blows the w h i s t l e a t the proper times.) STOP." During the second t r i a l an a u d i t o r y d i s t r a o -t i o n was s u p p l i e d by means o f the t r a f f i c s o u n d - e f f e c t s re o o r d . The i n s t r u c t i o n s , w i t h m o d i f i c a t i o n s not ed, were the same as those f o r the p r a c t i c e t e s t . The t h i r d t r i a l was ad m i n i s t e r e d immediately a f t e r the second t r i a l w i t h a la p s e o f time o n l y s u f f i -c i e n t t o change the t e s t papers and r e p l a c e the t r a f f i c r e c o r d with t h e mus i o a l number. In each case the - 26 -i n t e r v a l between t e s t s was approximately t h r e e to f o u r minutes. The i n s t r u c t i o n s g i v e n were the same as f o r the second t r i a l . The f o u r t h t r i a l was the c o n t r o l t e s t used to compare wit h the p r e v i o u s two t e s t s . It was done i n s i l e n c e . The i n s t r u c t i o n s were the same as i n the two p r e v i o u s t r i a l s . The experiment was conducted d u r i n g February and March o f 1941. A l l the rooms used were adequately l i g h t e d and o f a normal school temperature. Hone o f the s c h o o l s was on a busy thoroughfare, hence any con-d i t i o n i n g due to e x t e r n a l n o i s e s was r e l a t i v e l y equiva-l e n t f o r a l l groups. A l l t e s t i n g was done by the experimenter w i t h £2 to 38 s u b j e c t s o f the v a r i o u s age groups, with the e x c e p t i o n o f the 15-year age l e v e l , the three s e c t i o n s of. which (95 s u b j e c t s ) met t o g e t h e r f o r the t e s t . Two s e c t i o n s o f the 18-year age group (64 subjeots) were a l s o t e s t e d at one time. In the oase o f the 15-year-o l d s , two a s s i s t a n t s helped i n the c o l l e c t i n g and d i s -t r i b u t i n g o f the t e s t papers, and seeing t h a t these were p r o p e r l y f i l e d . One a s s i s t a n t aided the e x p e r i -menter wi t h the two combined s e o t i o n s o f the 18-year-o l d group. CHAPTER IV STATISTICAL ANALYSIS OF TEST DATA. A study o f the s t a t i s t i c a l data accumulated by means o f the t e s t s o u t l i n e d p r e v i o u s l y i s presented i n t h i s chapter. The method i n v o l v e d the r e d u c t i o n o f the raw scores to averages and the a p p l i c a t i o n o f a p p r o p r i a t e procedures to these averages. The purpose o f t h i s s t a t i s t i c a l e v a l u a t i o n was to determine i f any or a l l p a r t s o f the t h r e e f o l d problem under i n v e s t i g a t i o n had been solved. The procedures used c o n s i s t e d o f the c a l c u l a t i o n o f the standard d e v i a t i o n , the standard e r r o r o f the mean and the s i g n i f i c a n c e o f the d i f f e r e n c e s o f the means. Table II shows the average ages o f each o f the fo u r groups o f s u b j e c t s . •TABLE I I AVERAGE AGE OF SUBJECTS IN EACH AGE GROUP Age Group No. o f S u b j e c t s Average Age Age Range 9 y r . 85 9 y r . 8 y r 9 mo—9 y r 3 mo. 12 y r . 86 11 y r 11 mo. 11 y r 9 mo—12 y r 3 mo. 15 y r . . 95 14 y r 11 mo. 14 y r 9 mo—15 y r 3 mo. 18 y r . 95 18 y r . 17 y r 9 mo--18 y r 3 mo. From Table II i t i s seen t h a t there were - 28 -approximately the same number o f s u b j e c t s i n each group and that the average ages were almost e x a c t l y n i n e , twelve, f i f t e e n and e i g h t e e n y e a r s . A l l s u b j e c t s used i n t h i s experiment f e l l w i t h i n the ranges i n d i c a t e d . Table I I I c o n t a i n s the average i n t e l l i g e n c e q u o t i e n t s where o b t a i n a b l e , f o r the s u b j e c t s used i n the experiment. TABLE I I I AVERAGE INTELLIGENCE QUOTIENT OF SUBJECTS IN EACH AGE GROUP Age Group No. of S u b j e c t s Average I.Q. 9 year 26 110.5 12 year 64 111.9 15 year 95 108.3 18 y e a r 95 111.1 With the e x c e p t i o n of the nine-year age group f o r which i n t e l l i g e n c e t e s t data were a v a i l a b l e f o r o n l y 26 subjeots, Table I I I suggests that average i n t e l l i g e n c e q u o t i e n t s were s i m i l a r . I t should be poi n t e d out, how-ever, t h a t no attempt i s made to r e l a t e i n t e l l i g e n c e q u o t i e n t s to a b i l i t y to c a n c e l numbers. T h i s t a b l e i s i n c l u d e d p r i m a r i l y to show t h a t i n t e l l i g e n c e i s probably not a f a c t o r i n a c c o u n t i n g f o r the r e s u l t s o b t a i n e d . The r e s u l t s presented i n Table IV are obtained - 2 9 -by averag ing the t o t a l number o f d i g i t s scanned i n r e c o g -n i z i n g and c a n c e l l i n g the d e s i g n a t e d numerals w i t h i n the p r e s c r i b e d time l i m i t . The mean, the standard d e v i a t i o n and the standard e r r o r o f the mean f o r each sex, age group, and t r i a l are p r e s e n t e d . As no use was made o f the r e s u l t s o b t a i n e d from the p r a c t i c e t r i a l , they have been o m i t t e d . TABLE IV MEAN, STANDARD DEVIATION AND STANDARD ERROR OF THE MEAN FOR EACH EXPERIMENTAL CONDITION BY AGE AND SEX. T r i a l with Traffic Sounds T r i a l with Music T r i a l During Silence Sex Age No. of Mean Stand. Standard Mean Stand. Standard Mean Stand. Standard Group Subjects Devia. Error of Devia. Error of Devia. Error of The Mean The Mean The Mean Boy Boy Boy Boy G i r l G i r l G i r l G i r l 9 12 18 9 12 15 18 44 48 52 47 41 38 a 346.0 561.8 643.6 844.4 404.5 649.3 744.3 893.7 •78.5 110.6 126.3 115.1 92.4 115.6 121.5 138.7 11.9 16.0 17.5 16.7 14.4 18.6 18.4 20.2 368.6 566.6 686.6 862.5 402.2 655.1 796.3 859.2 85.1 104.4 124.2 116.2 8I.3 119.8 127.7 132.4 12.9 15.1 16.8 12.7 19.3 19.3 19.3 578.3 692.I 878.1 394.3 647.0 777.6 894.6 91.6 105.9 127.0 112.6 116.8 117.2 127.1 13.9 15.3 * 17.6 I6.3 12.3 18.8 17.8 18.3 - 31 -A c u r s o r y examination o f Table IV suggests the p o s s i b i l i t i e s o f the presence o f age and sex. d i f f e r e n c e s i n a b i l i t y to c a n c e l d i g i t s . I t appears d o u b t f u l that experimental c o n d i t i o n s per se c o n s i s t e n t l y e i t h e r i n -crease or decrease s c o r e s . The s i g n i f i c a n c e o f c e r t a i n d i f f e r e n c e s w i l l now be c o n s i d e r e d . In Table V mean d i f f e r e n c e s found by s u b t r a c t -i n g average s c o r e s of younger groups from o l d e r groups, the standard e r r o r o f these d i f f e r e n c e s and the s i g n i f i -cance o f these d i f f e r e n c e s are presented f o r the two sexes s e p a r a t e l y , f o r each experimental c o n d i t i o n . Soores used i n t h i s t a b l e as i n T a b l e IV are o b t a i n e d i n terms o f t o t a l number o f d i g i t s scanned. T A B L E V S I G N I F I C A N C E OF T H E D I F F E R E N C E S BETWEEN MEAN S C O R E S OF V A R I O U S A G E G R O U P S , S E X E S S E P A R A T E , F O R E A C H E X P E R I M E N T A L C O N D I T I O N . C o m p a r i s o n o f T r i a l w i t h T r a f f i c s o u n d s T r i a l w i t h M u s i c T r i a l D u r i n g S i l e n c e A g e G r o u p s M e a n D i f f . s t a n d a r d i u r r o r o f D i f f . a i g n i f . o f t h e D i f f . M e a n D i f f . S t a n d a r d E r r o r o f D i f f . S i g n i f . o f t h e D i f f . M e a n j J i f f . S t a n d a r d E r r o r o f D i f f . S i g n i f . o f t h e D i f f . Boys 18-15 lS.^12 18- 9 15-12 15- 9 12- 9 200.8 282.6 498.4 81*8 297.6 215.8 24.19 23.13 20.31 23.71 20.97 19 .74 8.26 12.27 24.53 3.45 14.19 10.97 175.9 295.9 493.9 120.0 318.0 I 9 8 . O 24.06 22.53 21.10 22.98 21.58 19.85 7.30 13.16 23.41 5.10 14.72 9.97 186.0 298.8 529.0 113.8 343.0 229.2 24.03 22.36 21.42 23.32 22.42 20.67 7.75 13.39 24.72 4.89 15.31 11.06 G i r l s 1 18-15 18-12 18- 9 15-12 15- 9 12- 9 149.4 244.4 489.2 95.0 339.g 244.8 27.32 27.46 24.81 26.15 23.37 23.52 5.46 8.87 I 9 . 7 I 3.64 .14.53 I O . 4 3 62.9 204.1 457.0 141.2 394.1 252.9 27.30 27.30 23.10 27.30 23.10 23.10 2.30 7.48 19.78 5.16 17.06 10.95 117.0 247.6 500.3 130.6 383.3 252.7 27.42 26.24 22.05 25.89 21.63 22.47 4 .27 9.47 22.77 5.06 17.73 11.24 - 3 3 -A n a l y s i s o f r e s u l t s g i v e n i n Table V bears out the h y p o t h e s i s o f the presence o f age d i f f e r e n c e s . F o r each experimental c o n d i t i o n and f o r each sex, o l d e r sub-j e c t s made h i g h e r scores than younger s u b j e o t s . In each i n s t a n c e except that o f the 15 and 18-year o l d g i r l s d u r i n g the t r i a l with musio sounds, the d i f f e r e n c e exceeds three times i t s standard e r r o r . Table VI shows the s i g n i f i o a n o e o f the d i f f e r -ences i n mean s c o r e s obtained f o r each experimental con-d i t i o n by age and sex. TABLE VT SIGNIGICANCE OF THE DIFFERENCES BETWEEN MEAN SCORES FOR EACH EXPERIMENTAL CONDITION BY AGE AND SEX. T r i a l D u r i n g S i l e n c e Minus T r i a l With T r a f f i c Sounds (Mean S c o r e s ) . T r i a l D u r i n g S i l e n c e Minus T r i a l W i t h Music (Mean S c o r e s ) . T r i a l W i t h Music Minus T r i a l With T r a f f i c Sounds (Mean S c o r e s ) . Age Group D i f f . S tandard E r r o r o f D i f f . S i g n i f . of D i f f . D i f f . - S tandard E r r o r o f D i f f . S i g n i f . o f D i f f . B i f f . S tandard E r r o r of D i f f . S i g n i f . of D i f f . Boys lb 15 12 9 4cj.5 1 6 . 5 3 -1 23 . 3 4 2 4 . 83 2 2 . 15 1 8 . 3 0 1.45 1 .95 O .76 0 . 1 7 1 5 . 6 5 .5 11 .7 - 1 9 . 5 23 . 4 0 . 2 4 . 69 2 1 . 50 I 8 . 9 6 O .67 0 .22 0 .54 - 1 . 0 3 18 .1 4 3 . 0 4 . 8 22 .6 23 .70 24 .60 22.00 17.56 0.764 I . 7 6 0 . 2 2 1.28 G i r l s 2 7 . 2 6 2 5 . 6 0 26 . 44 18 . 94 26.60 2:6.26 26.94 17.68 l o 15 12 9 • 9 33-3 - 2 . 3 - 1 0 . 2 0 . 0 3 1 . 3 0 - 0 . 0 8 7 - 0 . 5 7 3 5 . 4 - 1 8 . 7 - 8 . 1 - 7 . 9 1 . 3 3 - 0 . 7 1 - 0 . 3 0 - 0 . 4 5 - 3 4 . 5 5 2 . 0 5 . 8 - 2 . 3 27 .94 2 6 . 8 0 19.20 -1 .24 I . 9 6 0 . 2 2 - 0 . 1 2 - 35 -The o u t s t a n d i n g f e a t u r e o f Table VI i s the absence o f any s i g n i f i c a n t d i f f e r e n c e s f o r the t h r e e t e s t c o n d i t i o n s at a l l ages and f o r both sexes. T h i s means that the t e s t s have f a i l e d to i n d i c a t e d i s t r a c t i o n e f f e c t s w i t h i n the c o n f i n e s o f the experiment. Such d i f f e r e n c e s as obtained are p r o b a b l y due to chance f a c t o r s t h a t are i n h e r e n t i n the t e s t s i t u a t i o n . Table VII shows the s i g n i f i c a n c e o f sex d i f f e r -ences f o r the f o u r age groups f o r each experimental con-d i t i o n . TABLE VII SIGNIFICANCE OF THE DIFFERENCES BETWEEN MEAN SCORES OF THE TWO SEXES AT THE FOUR AGES FOR EACH EXPERIMENTAL CONDITION. T r i a l With T r a f f i c Sounds T r i a l With Music T r i a l During Silence Age Group D i f f . Standard Error of D i f f . S i g n i f . of D i f f . D i f f . Standard Error of D i f f . S i g n i f . of D i f f . D i f f . Standard Error of D i f f . S i g n i f . of D i f f . 18 49-3 26 .20 1.88 - 3 . 3 25.59 - 0 . 1 2 9 16.5 24 .50 0.67 15 100.9 25.39 3.98 109.7 25.92 4.25 85-5 25.03 3.43 12 87.5 " 24 .53 3.57 88.5 24 .50 3 .61 6 8 . 7 24.24 2.84 9 58.5 18.70 3.13 33.6 16.70 2 .01 45 .2 18.56 2.43 - 37 -I t i s to be seen i n Table VII t h a t at the 12 and 15-year age l e v e l s the g i r l s show marked s u p e r i o r -i t y . At the n i n e - y e a r age l e v e l under the t r a f f i c con-d i t i o n the g i r l s are a l s o s i g n i f i c a n t l y s u p e r i o r and the o t h e r two t r i a l s approach s i g n i f i c a n c e . At the 18-year age l e v e l none o f the d i f f e r e n c e s i s s i g n i f i c a n t . Although these d i f f e r e n c e s do not p o i n t c o n c l u s i v e l y to a sex d i f f e r e n c e i n a l l cases, the i n d i c a t i o n s o f such a d i f f e r e n c e being present are s u f f i c i e n t l y strong to make i t i n a d v i s a b l e to combine the boys' and g i r l s ' s c o r e s f o r s t a t i s t i c a l treatment. The e r r o r f a c t o r i n t h i s experiment i s o f secondary importance s i n c e the s u b j e o t s were informed o f the number o f d i g i t s ( f i v e ) t o be marked i n each l i n e o f the t e s t and, as a r e s u l t , they r a r e l y omitted a d i g i t to be c a n c e l l e d . The e r r o r score c o n s i s t s o f the average number o f the designated numerals which were not marked i n the completed p o r t i o n o f the t e s t . T able V I I I c o n t a i n s the average e r r o r and percentage e r r o r f o r boys and g i r l s a t eaoh age l e v e l and f o r each o f the three t r i a l s . Percentage e r r o r was ob-t a i n e d i n terms o f the designated numerals omitted as compared w i t h the t o t a l number o f designated d i g i t s i n the p o r t i o n scanned. TABLE VIII AVERAGE ERROR AND PERCENTAGE ERROR FOR EACH AGE LEVEL BY SEX FOR EACH EXPERIMENTAL CONDITION. T r i a l T r a f f i c with Sounds. T r i a l With Music. T r i a l During Silence. Sex Age Group No. of Subjects Average Error Percent Error Average Error Percent Error Average Error Percent Error Boy 9 44 2.89 8 . 4 1.93 5.2 2.66 7.6 Boy 12 48 2.62 4 . 7 2.46 4 . 3 1.71 4 . 1 Boy 15 52 ^ 2.25 3.5 2.58 3.8 2.37 3-4 Boy 18 47 I . 9 6 2 . 3 2.27 2.6 2.42 2.6 G i r l 9 41 2.25 5-6 1.97 4 . 9 1.72 4 . 4 G i r l 12 38 2.02 3 . 1 2.51 3.8 1.59 2.5 G i r l 15 43 2.01 2.7 2.20 2.8 2.45 3.2 G i r l 18 48 1.06 1.2 1.85 2 . 2 0 . 9 1 •1.0 r - 39 -An a n a l y s i s o f Table V I I I shows, t h a t the average e r r o r f o r both sexes at the f o u r age l e v e l s i s p r a o t i o a l l y uniform; The s i z e o f the e r r o r i s not considered to be l a r g e when t a k e n . i n r e l a t i o n to the number o f d i g i t s ssanned. A comparison o f the average e r r o r w i t h the t o t a l number o f c a n c e l l a b l e d i g i t s shows a g e n e r a l decrease i n the percentage e r r o r w i t h i n c r e a s i n g age. In c o n j u n c t i o n with t h i s percentage deorease, i t i s to be noted that the g i r l s have a s l i g h t l y s m a l l e r percentage e r r o r than the boys i n a l l comparable s i t u a t i o n s . CHAPTER V CONCLUSION: AN INTERPRETATION OF TEST DATA. The present experiment was performed to d i s -cover i f , w i t h i n the l i m i t a t i o n s set f o r t h , the Woodworth and W e l l s Numbers C a n c e l l a t i o n Test would measure any e f f e c t s r e s u l t i n g from a u d i t o r y s t i m u l i , i f the t e s t would show sex d i f f e r e n c e s , and f i n a l l y , i f the t e s t would, r e v e a l age d i f f e r e n c e s i n the a b i l i t y o f a group o f s u b j e c t s to c a n c e l d i g i t s . The r e s u l t s o f t h i s experiment show that the d i f f e r e n c e s i n scores obtained f o r the f o u r age l e v e l s used are s t a t i s t i c a l l y s i g n i f i c a n t . A number o f p o s s i -b l e f a c t o r s c o n t r i b u t e to t h i s r e s u l t . The o l d e r sub-j e c t s are not e a s i l y d i v e r t e d from the task by the n o v e l t y o f the experiment. The o l d e r s u b j e o t s a r e a l s o more, f a m i l i a r w i t h the t e s t m a t e r i a l . The 15 and 18-year o l d s u b j e c t s , by reason o f t h e i r ages, have had l o n g e r c l o s e a s s o c i a t i o n with numbers and, as a r e s u l t , may be a b l e to re c o g n i z e them more r e a d i l y . These two f a c t o r s o f f a m i l i a r i t y w i t h t e s t s and fami-l i a r i t y w i t h numbers p o s s i b l y have some e f f e o t on the r e s u l t s o f the t e s t . Probably, however, the outstand-i n g f a c t o r i s the r e d u c t i o n o f the r e a c t i o n time i n each s u c c e s s i v e l y o l d e r group ( 4 5 ) . - 41 -The e f f e c t s o f t r a f f i c sounds and music on the s u b j e c t s , i n comparison with the e f f e c t s under q u i e t c o n d i t i o n s , are not s t a t i s t i c a l l y s i g n i f i c a n t . As was shown i n Table VI (See Page 34), the c r i t i c a l r a t i o s v a r i e d from -1.03 to 1.76 f o r these three ex-p e r i m e n t a l c o n d i t i o n s . A number of f a c t o r s may have caused t h i s r e s u l t . I t i s p o s s i b l e that the d i s t r a c t -i n g s t i m u l i were not o f s u f f i c i e n t s t r e n g t h or n o v e l t y to d i v e r t the a t t e n t i o n o f ' t h e s u b j e c t s from the t e s t . The s u b j e c t s may have been a b l e r e a d i l y to h a b i t u a t e the d i s t r a c t o r s , or the s u b j e c t s may have ignored the d i s t r a c t o r s e n t i r e l y . An i n c r e a s e i n e f f o r t may have r e s u l t e d i n the s u b j e c t s being a b l e to i n h i b i t the s t i m u l i and at the same time do as much work as, or even more work than, that done d u r i n g the q u i e t t r i a l . Another f a c t o r to be c o n s i d e r e d i s t h a t the d i s t r a c t -i n g s t i m u l i were not i n the same sensory f i e l d as the a t t e n t i o n s t i m u l i . The b r e v i t y of the t e s t may a l s o have c o n t r i b u t e d to the l a c k o f d e f i n i t e d i s t r a c t i n g e f f e o t s . A c o n s i d e r a b l y l o n g e r t e s t might have pro-duced r e s u l t s t h a t would show evidence o f d i s t r a c t i o n . Such a l o n g e r t e s t , however, might have produced f a t i g u e o r boredom, which i n themselves aot as d i s -t r a c t o r s . I t would be extremely d i f f i c u l t to d e t e r -mine whether the experimental s i t u a t i o n or the i n t e r -n a l c o n d i t i o n s o f the s u b j e c t s were r e s p o n s i b l e f o r - 42 -the apparent d i s t r a c t i o n e f f e c t s that might be o b t a i n e d . A c o n d i t i o n which seems t o have a f f e o t e d the r e s u l t s c o n s i d e r a b l y i s the wide range o f I n d i v i d u a l ' s c o r e s t h a t composed the mean score f o r each t r i a l . Had th e r e not been such a great d i s p a r i t y i n i n d i v i d u a l scores, the standard d e v i a t i o n s o f the mean a l s o would have been c o n s i d e r a b l y smaller, with the r e s u l t t h a t the c r i t i c a l r a t i o s might have had s i g n i f i c a n c e . The data concerning sex d i f f e r e n c e s show t h a t the performance of g i r l s tends to be s u p e r i o r to that o f boys. In Table V II (Page 36) i t i s to be seen t h a t , i n s i x cases out o f twelve, the c r i t i c a l r a t i o s f o r sex d i f f e r e n c e s are over 3.0, and i n three a d d i -t i o n a l cases the r a t i o s were 2.0 or g r e a t e r . T h i s was considered to be s u f f i c i e n t to show a d e f i n i t e sex d i f f e r e n c e . The most s u i t a b l e e x p l a n a t i o n o f t h i s d i f f e r e n c e appears to be i n e a r l i e r m a t u r i t y o f hand-eye c o - o r d i n a t i o n and r e a c t i o n time i n g i r l s than i n boys ( 4 5 ) . I t i s p o s s i b l e t h a t t h i s sex d i f f e r e n c e would disappear e n t i r e l y w i t h a d u l t subjeots. Such a p o s s i b i l i t y i s supported by the present experiment i n t h a t the c r i t i c a l r a t i o s at the 18-year age l e v e l are a l l l e s s than 3.0, while two o f those at the 12 and a l l at the 15 ye a r l e v e l are over 3.0. I t i s f u r t h e r p o s s i b l e t h a t t h i s sex d i f f e r e n c e i s a tem-por a r y c o n d i t i o n i n t h a t o n l y one o f the sex - 43 -d i f f e r e n c e s at the nin e - y e a r l e v e l i s s i g n i f i c a n t . T h i s suggests t h a t sex d i f f e r e n c e s are j u s t beginning to appear at age nine and th a t at lower age l e v e l s they might not be apparent. With r e f e r e n o e to the e r r o r f a c t o r , the data suggest that there i s a p r o g r e s s i v e decrease i n the percentage o f e r r o r s made f o r each o l d e r group, w h i l e the absolute number o f e r r o r s remains r e l a t i v e l y u n i -form at a l l ages. T h i s r e d u o t i o n o f e r r o r s i n r e l a t i o n to output may be due to two f a c t o r s . Increase i n age r e s u l t s i n g r e a t e r f a m i l i a r i t y w i t h the t e s t m a t e r i a l , and consequently an i n c r e a s e i n a b i l i t y to s e l e c t cor-r e c t symbols. The i n s t r u c t i o n s , i n d i c a t i n g the number of symbols to be c a n c e l l e d i n each l i n e may have had g r e a t e r s i g n i f i c a n c e to the o l d e r s u b j e c t s and made them more a l e r t than the younger ones. There appear-to be no l a r g e e r r o r d i f f e r e n c e s between boys and g i r l s . In comparing the c o n c l u s i o n s o f t h i s e x p e r i -ment w i t h those o f p r e v i o u s r e s e a r c h e s , i t i s to be noted t h a t , as i n the i n v e s t i g a t i o n s o f C a s s e l and Dallenbaoh ( 8 ) , T i n k e r (41), and J e n k i n s (25), no measurable d i s t r a c t i o n e f f e c t was observed. P o s s i b l y the f a c t o r s o f experimental s t r u c t u r e , subject adjus-t a b i l i t y and bimodal sensory s t i m u l a t i o n , which may have a f f e c t e d the i n v e s t i g a t i o n s mentioned, a l s o con-- 44 -t r i b u t e d to the l a c k o f c o n c l u s i v e r e s u l t s i n t h i s experiment. With r e f e r e n c e to the c o n c l u s i o n s made i n the present i n v e s t i g a t i o n concerning age and sex d i f f e r -ences, no b a s i s f o r comparison i s p o s s i b l e , since a v a i l a b l e r e p o r t s f a i l e d to d i s c u s s these two f a c t o r s . The m a t u r a t i o n a l e f f e c t s observed i n the pr e s e n t study, however, are c o n s i s t e n t with f i n d i n g s r e p o r t e d by other i n v e s t i g a t o r s ( 4 5 ) . The present experiment makes t h r e e worthwhile c o n t r i b u t i o n s to the problem o f a u d i t o r y d i s t r a c t i o n . F i r s t , the r e s u l t s i n d i c a t e d e f i n i t e age d i f f e r e n c e s i n a b i l i t y to c a n c e l numerals under s p e c i f i c experimen-t a l c o n d i t i o n s . Second, s t a t i s t i c a l l y s i g n i f i c a n t sex d i f f e r e n c e s are shown i n the Numbers C a n c e l l a t i o n Test at the 12 and 15-year l e v e l s . T h i r d , w i t h i n the e x p e r i -mental c o n d i t i o n s p r e s c r i b e d i n the present i n v e s t i g a -t i o n , e f f e c t s o f a u d i t o r y d i s t r a c t i o n f o r b r i e f p e r i o d s o f time are not s i g n i f i c a n t . In a d d i t i o n " to these f i n d i n g s which bear on a c t u a l r e s u l t s obtained, the experiment suggested f u r t h e r r e s e a r c h i n t h i s f i e l d along the f o l l o w i n g l i n e s . F i r s t , f u r t h e r i n v e s t i g a t i o n to determine i f an age might be reached at' which no improvement i n output i s s t a t i s t i c a l l y apparent. Second, sex d i f f e r -ences might be i n v e s t i g a t e d to determine i f they are absent i n younger s u b j e c t s and disappear i n o l d e r sub-j e c t s . T h i r d , d i s t r a c t i o n e f f e c t s might be i n v e s t i g a t e d - 45 -w i t h l a r g e r groups o f sub j e o t s o f the same age and sex i n o r d e r to c o n t r o l m a t u r a t i o n a l e f f e c t s and sex d i f f e r -ences. F o u r t h , a thorough i n v e s t i g a t i o n o f such f a c t o r s as m o t i v a t i o n , energy consumption, f a t i g u e , and e x t r a n -eous ohance f a c t o r s , might be undertaken. With b e t t e r c o n t r o l o f these f a o t o r s , a more ac c u r a t e measurement o f the e f f e c t s o f d i s t r a c t i o n should be p o s s i b l e . F i f t h , the d i s t r a c t i n g s t i m u l i presented might be v a r i e d i n an attempt to d i s c o v e r the e f f e c t s o f a wider range of s t i m u l i on the output o f human beings. The t e s t m a t e r i a l used o f f e r s a c o n s i d e r a b l e number o f p o s s i b l e a p p l i c a t i o n s f o r t h i s type o f r e s e a r c h i n that i t r e q u i r e s a h i g h degree o f a t t e n t i o n and, at the same time, by i t s r e l a t i v e s i m p l i c i t y , appears to resemble a number o f r o u t i n e t a s k s i n everyday l i f e . SUMMARY The c h i e f f i n d i n g s o f the present experiment may be summarized as f o l l o w s : 1. A u d i t o r y d i s t r a c t i o n s i n the form o f recorded music and t r a f f i c sounds had no s t a t i s t i c a l l y s i g n i f i c a n t e f f e c t s upon work accomplishment i n the Woodworth and W e l l s Numbers C a n c e l l a t i o n T e s t . 2. Performance on the Woodworth and W e l l s Numbers Can-c e l l a t i o n T e s t c o n s i s t e n t l y i n c r e a s e d w i t h age i n the case o f the nine, 12 and 15-year age groups s t u d i e d . 3. The performance o f g i r l s on the Woodworth and W e l l s Numbers C a n c e l l a t i o n T e s t tends to be s u p e r i o r to the performance o f boys. These sex d i f f e r e n c e s are s t a t i s t i c a l l y s i g n i f i c a n t under the three e x p e r i -mental c o n d i t i o n s at the 15-year age l e v e l . Two c o n d i t i o n s at the 12-year l e v e l and one a t the nine-year l e v e l a l s o show s i g n i f i c a n t d i f f e r e n c e s i n f a vour o f g i r l s . 4. In the case of both boys and g i r l s f o r the three t e s t c o n d i t i o n s the percentage e r r o r i s i n v e r s e l y p r o p o r t i o n a l to age. As a r e s u l t o f the present experiment a number o f problems f o r f u r t h e r r e s e a r c h have been suggested. 1. The age f a c t o r might be i n v e s t i g a t e d f u r t h e r to - 47 -determine i f m a t u r a t i o n a l e f f e c t s d i s appear. That i s , t o f i n d at what age t h e r e i s no f u r t h e r improve-ment i n performance on the Woodworth and W e l l s Numbers C a n c e l l a t i o n T e s t . 2. Sex d i f f e r e n c e s might be s t u d i e d to d i s c o v e r i f they are merely temporary c o n d i t i o n s . I t may be t h a t t h e r e are no sex d i f f e r e n c e s i n younger s u b j e c t s and th a t sex d i f f e r e n c e s d i sappear i n s u b j e c t s o l d e r than those used i n t h i s experiment. . 3. F u r t h e r work might, be done on d i s t r a c t i o n w i t h age and sex f a c t o r s c o n t r o l l e d . I f l a r g e r groups o f the same sex and age were used, a f i n e r measure o f d i s -t r a c t i o n e f f e c t s might be made. 4. P o s s i b i l i t y o f e s t a b l i s h i n g b e t t e r c o n t r o l o f such f a c t o r s as m o t i v a t i o n , energy consumption, f a t i g u e and extraneous chance f a c t o r s might be i n v e s t i g a t e d . 5 . The d i s t r a c t i o n e f f e c t s o f a more comprehensive range of s t i m u l i might be undertaken. Monotonous sleep-producing s t i m u l i , unpleasant h i g h - p i t c h e d n o i s e s , and d i f f e r e n t t y p es o f f a c t o r y and i n d u s t r i a l sounds might be employed. - 48 -A P P E N D I X The Woodworth and Wells Numbers Cancellation Test as used in the present experiment i s presented below. . 5 168492370 12750486934 18902 563717560892437869043 125 78051342692409761538320415796848126739053790865214 3597846102518237496085932410769345208 6179316758402 2739650814973615 0 2 84047859 621309315648724235679081 42530179 8 6 3860915472936748012564931207586127490538 947038562 16093827145781096 43525279416380 1048237956 09825617438354692017602 137 958421849570360952186743 10462795380628439751274560389135078421695681924370 86149230574517286309195683274086207354912473501869 63217084957941503826563271840970683915248504312697 79621340584251938607904817 2365628305 1497594807 1236 9681053742194537026804723 8 659190368271547503294168 07342918659612487 053198306547215793482608359726401 3476812590630759481248597312 0671029645383471652890 65973284010836149725253469018 7 5417283 9 0 61265830749 83509472168570213946521084763927451906836897103524 18097653242784651390312695 874048205 163794180569372 2048576139716 8025439670142 395806947328 152016487953 41256809735093762184869751402383516790429624315 087 521340968 7 3429806571736520981439684057210732948615 BIBLIOGRAPHY 1. 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