This report aimed to replicate Stroop's (1935) experiment. Using the repeated measures design and a sample of 20 students, differences in verbal reaction times on two tests were observed.

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An Experiment into the Effect of Interference on Verbal Reactions                          -  -

Abstract

This report aimed to replicate Stroop’s (1935) experiment. Using the repeated measures design and a sample of 20 students, differences in verbal reaction times on two tests were observed. The one-tailed hypothesis predicted that it would take longer to say words in the Cc, this is the conflicting condition where the colour of the word differs from the colour that the word describes. It was found that, using the t-test for related data, this hypothesis could be accepted as the obtained value was much greater then the critical value. It can therefore be concluded that visual interference does affect people’s verbal reactions.


Introduction

In 1935 John Ridley Stroop published his Ph.D. thesis entitled ‘Studies of Interference in Serial Verbal Reactions’ - the findings of which became known as ‘the Stroop Effect’. Stroop mentioned many studies in his work but the two that are most relevant for this report are Brown (1915) and Telford (1930), they conducted very similar investigations into colour associations and colour recognition patterns respectively. This area of research is known as controlled and automatic processing, it involves studies into how humans cope with divided attention such as multi-tasking. This could be anything from the simple dishwashing and listening to music simultaneously, to complex shadowing of continuous prose presented in one ear, whilst also typing up a separate prose presented to the other ear via headphones (Shaffer 1975). With their two-process theory, Shiffrin and Schneider (1977) make useful distinctions between controlled and automatic processing. They are as follows: controlled processing seems to need focused attention and requires multi-tasking to be minimised as much as possible, whereas automatic processes aren’t affected by multi-tasking and they do not require focused attention. However, automatic processes are hard to amend once learnt. Kahneman proposed his capacity/resource allocation model in 1973 (see Figure 1):

Figure 1

This model could provide an explanation for the Stroop Effect as the visual interference of the conflicting colour could be described as a momentary intention (a voluntary shift of attention). This is because the participant has to force his/herself to read the word and not say the colour of it. This therefore means that, according to Kahneman, the central processor has trouble deciding between tasks (in this case, between reading the actual word or the colour of it). This could be an explanation for the expected delay in the condition where the colour of the word is different to the colour that the word describes.


Aims and Hypotheses

Aim

The aim of this report is to replicate Stroop’s original (1935) experiment.

Alternative Hypothesis

Words that are coloured in conflicting colours to that which the text describes (conflicting condition, Cc) will take significantly longer to process than words coloured in the same colour that the text describes (similar condition, CS). This is a one-tailed (directional) hypothesis.

Null Hypothesis

The colour interference does not affect the participants so therefore the process times for both conditions will be similar; any differences are due to chance.

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Method

Design and Controls

This report has been based on the repeated measures design. The main reason for this is that individual differences are eliminated and the time period for which to execute the experiment is minimised. This design, however, introduces order effects which include fatigue and practice effects. These effects can be minimised through counterbalancing, this involves splitting the participants into two equal groups. The first group will go through the experiment from CS to CC and the second group from CC to CS. This is known as ABBA counterbalancing.

The data will consist of two sets of times, one ...

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