Journal of
Experimental Psychology
VOL. XVIII, No. 6 DECEMBER, 1935
STUDIES OF INTERFERENCE IN SERIAL VERBAL REACTIONS
BY J. RIDLEY STROOP»
George Peabody College
INTRODUCTION
Interference or inhibition (the terms seem to have been used almost indiscriminately) has been given a large place in experimental literature. The investigation was begun by the physiologists prior to 1890 (Bowditch and Warren, J. W., 1890) and has been continued to the present, principally by psychologists (Lester, 1932). Of the numerous studies that have been published during this period only a limited number of the most relevant reports demand our attention here.
Miinsterberg (1892) studied the inhibiting effects of changes in common daily habits such as opening the door of his room, dipping his pen in ink, and taking his watch out of his pocket. He concluded that a given association can function automatically even though some effect of a previous contrary association remains.
Mviller and Schumann (1894) discovered that more time * The writer wishes to acknowledge the kind assistance received in the preparation
of this thesis. He is indebted to Dr. Joseph Peterson for encouragement, helpful suggestions, and criticism of the manuscript; to Major H. W. Fenker, a graduate student in psychology, for helpful suggestions relative to preparation of the manu- script; to Drs. J. Peterson, S. C. Garrison, M. R. Schneck, J. E. Caster, O. A. Simley, W. F. Smith, and to Miss M. Nichol for aid in securing subjects; to some three hundred college students who served as subjects; and to William Fitzgerald of The Peabody Press for substantial assistance in the printing of the test materials.
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was necessary to relearn a series of nonsense syllables if the stimulus syllables had been associated with other syllables in the meantime. From their results they deduced the law of associative inhibition which is quoted by Kline (1921, p. 270) as follows: “If a is already connected with b, then it is diffi- cult to connect it with k, b gets in the way.” Nonsense syl- lables were also used by Shepard and Fogelsonger (1913) in a series of experiments in association and inhibition. Only three subjects were used in any experiment and the changes introduced to produce the inhibition were so great in many cases as to present novel situations. This latter fact was shown by the introspections. The results showed an in- crease in time for the response which corresponded roughly to the increase in the complexity of the situation. The only conclusion was stated thus: “We have found then that in acquiring associations there is involved an inhibitory process which is not a mere result of divided paths but has some deeper basis yet unknown” (p. 311).
Kline (1921) used ‘meaningful’ material (states and capitals, counties and county seats, and books and authors) in a study of interference effects of associations. He found that if the first associative bond had a recall power of 10 per- cent or less it facilitated the second association, if it had a recall power of 15 percent to 40 percent the inhibitory power was small, if it had a recall power of 45 percent to 70 percent the inhibiting strength approached a maximum, if the recall power was 70 percent to 100 percent the inhibition was of medium strength and in some cases might disappear or even facilitate the learning of a new association.
In card sorting Bergstrom (1893 and 1894), Brown (1914), Bair (1902), and Culler (1912) found that changing the arrangement of compartments into which cards were being sorted produced interference effects. Bergstrom (1894, p. 441) concluded that “the interference effect of an association bears a constant relation to the practice effect, and is, in fact, equivalent to it.” Both Bair and Culler found that the inter- ference of the opposing habits disappeared if the habits were practiced alternately.
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Culler (1912), in the paper already referred to, reported two other experiments. In one experiment the subjects associated each of a series of numbers with striking a parti- cular key on the typewriter with a particular finger; then the keys were changed so that four of the numbers had to be written with fingers other than those formerly used to write them. In the other experiment the subjects were trained to react with the right hand to ‘red’ and with the left hand to ‘blue.’ Then the stimuli were interchanged. In the former experiment an interference was found which decreased rapidly with practice. In the latter experiment the interference was overbalanced by the practice effect.
Hunter and Yarbrough (1917), Pearce (1917), and Hunter (1922) in three closely related studies of habit interference in the white rat in a T-shaped discrimination box found that a previous habit interfered with the formation of an ‘opposite’ habit.
Several studies have been published which were not pri- marily studies of interference, but which employed materials that were similar in nature to those employed in this research, and which are concerned with why it takes more time to name colors than to read color names. Several of these studies have been reviewed recently by Telford (1930) and by Ligon (1932). Only the vital point of these studies will be mentioned here.
The difference in time for naming colors and reading color names has been variously explained. Cattell (1886) and Lund (1927) have attributed the difference to ‘practice.’ Woodworth and Wells (1911, p. 52) have suggested that, “The real mechanism here may very well be the mutual interference of the five names, all of which, from immediately preceding use, are ‘on the tip of the tongue,’ all are equally ready and likely to get in one another’s way.” Brown (1915, p. 51) concluded ” t h a t the difference in speed between color naming and word reading does not depend upon practice” but that (p. 34) “the association process in naming simple objects like colors is radically different from the association process in reading printed words.”
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Garrett and Lemmon (1924, p. 438) have accounted for their findings in these words, “Hence it seems reasonable to say that interferences which arise in naming colors are due not so much to an equal readiness of the color names as to an equal readiness of the color recognitive processes. Another factor present in interference is very probably the present strength of the associations between colors and their names, already determined by past use.” Peterson (1918 and 1925) has attributed the difference to the fact that, “One particular response habit has become associated with each word while in the case of colors themselves a variety of response ten- dencies have developed.” (1925, p. 281.) As pointed out by Telford (1930), the results published by Peterson (1925, p. 281) and also those published by Lund (1927, p. 425) confirm Peterson’s interpretation.
Ligon (1932) has published results of a ‘genetic study’ of naming colors and reading color names in which he used 638 subjects from school grades 1 to 9 inclusive. In the light of his results he found all former explanations untenable (He included no examination of or reference to Peterson’s data and interpretation.) and proceeded to set up a new hypothesis based upon a three factor theory, a common factor which he never definitely describes and special factors of word reading and color naming. He points out that the com- mon factor is learned but the special factors are organic. He promises further evidence from studies now in progress.
The present problem grew out of experimental work in color naming and word reading conducted in Jesup Psy- chological Laboratory at George Peabody College For Teachers. The time for reading names of colors had been compared with the time for naming colors themselves. This suggested a comparison of the interfering effect of color stimuli upon reading names of colors (the two types of stimuli being presented simultaneously) with the interfering effect of word stimuli upon naming colors themselves. In other words, if the word ‘red’ is printed in blue ink how will the interference of the ink-color ‘blue’ upon reading the printed word ‘red’ compare with the interference of the
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