1 Gareth Stack - Lab Group 2 Date of practical - 20/10/03 / Date of Submission - 07/11/03
Reaction times related to congruence in a Stroop test of undergraduate students
The 'Stroop effect', a measure of interference in a reaction time task, was investigated. Twenty undergraduate students of mixed age and gender were each presented with 48 coloured words in turn. These were divided into 16 of each of 3 levels of congruence. The time required to identify the colour of each stimulus was recorded, and related to whether the word presented identified, contrasted with or contained an unrelated meaning to the font colour it was displayed in. This data was collected and compared in order to assess the median time taken to correctly respond to each level of congruence. The results confirmed the effect of interference on the identification of colour when presented with contrasting semantic cues. However additional inferential statistics are required to assess the significance of the variance found between response times to words with meanings unrelated to, and those with meanings equivalent to their font colour. It is suggested that additional experiments be carried out to control for the possible effects of the relative position of input keys, and to determine whether prior learning or a language bias in the perception of semantic information explains the results.
3 TABLE OF CONTENTS
Page No. 1. Title Page
Table of Contents
Appendix 1 – Table of Group and Experimenters Response times in Milliseconds
Appendix 2 – Additional Graphs
4 INTRODUCTION Since its development in 1935, the Stroop task, a measure of the effect of interference on performance of a colour identification task, has been used to investigate aspects of such varied psychological disorders as Attention Deficit Hyperactivity Disorder (Savitz, & Jansen, 2003), Schizophrenia (Gruber, 2002), and Anorexia (Mendelwitcz, Nef, & Simon, 2001). J. Ridley Stroop's original word colour identification test has additionally been modified to include numeric (Girelli, Sandrini, & Cappa, 2000) emotionally stimulating (Watts, Fraser, McKenna, Sharrock, Trezise, 1986) and auditory (Shor, 1993) variables.
In his classic experiment 'Studies of interference in serial verbal reactions' Stroop (1935) administered several variants of two main tests. Stroop (1935) referred to his tests as RCN, to stand for "Reading colour names", where participants were required to repeat the written meaning of words with differing coloured fonts; and NCW to stand for "Naming Coloured Words", in which participants were asked to verbally identify the font colour of each printed colour name. Additionally Stroop (1935) tested his participants at different stages of practise with each task, to account for the effects of association. Stroop (1935) identified an interference effect of prior learning on the time taken by participants to complete these tasks, an effect still pronounced despite continued practice at each task.
The current experiment attempted to verify whether the classic stroop effect would be displayed when the test was administered and participated in by undergraduate psychology students. It differed from Stroop’s (1935) original experiment both by presenting each stimulus individually rather than in a group and by including words that contained the same semantic meaning as their font colour.
Students were presented with a series of words of varying font colour and semantic meaning, and their response times related to the congruence of the semantic and colour information for each stimulus were collated and contrasted with the group of students as a whole.
5 When each meaning did not match, and yet both contained contradictory information participants should have been momentarily confused by the interference of their...
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