Stroop Effect Lab Report

Greta Warren – Lab Group 2

Date of practical - 24/10/2014 / Date of submission – 13/11/2014

Demonstrators – Shane and Tara

Effect of interference on reaction times in a colour identification task tested in undergraduates

__________ words ABSTRACT

A phenomenon known as the Stroop Effect, discovered by J. R. Stroop in 1935, was tested among a sample group of 54 undergraduate psychology students, of mixed gender and varying age range. Stroop found that reaction time in identifying a colour was significantly increased when presented in the form of a word describing a different or incongruent colour. 144 words, divided into four levels of congruence were presented on a computer monitor to each participant, who were then asked to respond as quickly

While this is a similar sample group to the one used by Stroop (1935) in his original research, the experiment differs in several ways, taking advantage of the advancement of technology since the 1930s; for example: the presentation of the stimuli on a computer screen rather than on paper, each word being presented individually rather than all together as a list, and the method of participant response being pressing a corresponding key rather than naming the colour out loud. The current experiment also includes an extra dimension with the addition of the ‘congruous’ and ‘semantic’ trial types, which were not used in the

1.1. Median reaction times of individual vs. group in milliseconds

The individual and group results were found to be alike in that in both cases the congruous response times were the fastest and incongruous the slowest, though the reaction times for this experimenter in regard to congruous and control trials were quite similar compared to the group’s, where the reaction time for the control trial was considerably longer than that for the congruous one.

In the case of the congruous trials, the experimenter’s median reaction time was almost identical to that of the group average, with a difference of just 0.5 milliseconds. With regard to the control and incongruous trials, the experimenter’s reactions followed the same pattern as the group’s (i.e. increasingly slower response times), though consistently below the class average, as did the standard deviations. In the semantic trials however, the individual’s response times deviated from this trend by exceeding the group’s average, with a much larger standard deviation.