J. Ridely Stroop was the man who first introduced the Stroop effect, coined after his own name, to modern psychology. In his 935 study Studies of Interference in Serial Verbal Reactions Stroop studied interferences effect on reaction times when asked to recite the words printed. He based his hypothesis off of prior works on interference and inhibition stating, that incongruence in the word-color pairing would result in an increased reaction time or an incorrect response. He conducted two versions of his experiment one with reading the word as the task and a second with naming the color of the print. For the first he utilized 70 (4 male, 56 female) undergraduate volunteers. This experiment consisted of four conditions, two lists with two forms, and participants were asked to read the lists as fast as they could without mistakes as the experimenter followed along on a list printed in black ink. Half read the lists in the order b, d2, d, b2 and the other half read them in the reverse order to account for practice or fatigue effect. The second part of the experiment utilized 00 volunteer undergrads with the task being to name the color not the word. Stroop found that word-color incongruence did not reliably increase the time when reading the words, but when naming colors the presence of words naming other colors increased the reaction times. He then concluded, The associations that have been formed between word stimuli and the reading response are evidently more effective than those that have been formed between color stimuli and naming response. (Stroop, 935) Though there was no formal statement of whether Stroops hypothesis was supported based on the findings it is clear that h
is hypothesis was partially supported. There is not much room for improvement, Stroop accounted for practice and fatigue effects within his methods and had a decent representation of the population. If I had to improve in anyway it would be to include more males in the study.
Zajano and Gorman in their 986 study, Stroop Interference as a Function of Percentage of Congruent Items, sought to validate the Stroop effect, while investigating the potential of additional contributors to response competition. They hypothesized: if the interference effect can be accounted for wholly in terms of such response competition, the mixed list used in the present study should result in a direct linear function of response times in relation to percentage of congruent items. (Zajano & Gorman, 986) Their experiment consisted of a one-factor within-subjects design, with 33 (3 female, 2 male) undergraduate students who volunteered to undergo the study. The subjects were then administered lists of varying color-word congruence levels, in a randomized order, followed by an additional 0% congruence list. The results showed that response competition caused the difference in reaction times, and with a 95% CI all points were significantly affected by this response competition. The authors concluded that due to the curvilinear nature of the data that the inhibition is consistent with that of selective attention caused through response inhibition. Their hypothesis was supported by their results. The only issue is this experiment has a lack of subjects; there are only 2 males with 3 females this is not a good representation of the population and therefore is unable to be generalized in a confident manner.