University of Essex

Department of Psychology

Research Methods in Psychology - PS114

Lab Report

Timeslot 12 pm

Interference and Facilitation Effects on a Stroop Task When Delaying the Stimulus Onset Asynchrony between 0 ms and 350 ms.

1402053

Date: 12.02.2015

Word count: 1947

Abstract
Experiments that include the interference and facilitation effects by using the stroop task, have given contradictory findings. The horse race model predicts that presentation of a colour word and a coloured patch at the same time, will produce interference effect when incongruent and facilitation when congruent. In the present study there was a delay between the presentations. Stroop facilitation and Stroop interference occurred in the present study, due to simultaneous presentation of incongruent word and colour interfered with colour patch naming, and simultaneous presentation of congruent word and colour facilitated with colour patch naming. Glaser and Glaser (1981) found that the highest interference was conducted at the lowest SOA’s, and did not find any facilitation effect. The present study confirmed the horse race model, as it showed that sufficient delay of the incongruent word stimulus, reduced interference to colour naming.

Introduction
Attention can be defined as selective aspect of response and perception, and theories about attention presupposes general framework of ideas of the perceptual system (Treisman, 1969). To fully understand attention, psychologists use different tasks and experiments. One example is the Stroop Task which gives rise to the Stroop effect. Stroop (1935) conducted two experiments to investigate interference effect. Stroop collected word stimulus that consisted of two dimensions; word dimension and the coloured word. He found that, when incongruent, the word dimension interfered with colour identification when presented at the same time. Stroop interference is explained as one dimension of a stimulus interfering with the processing of another dimension of that stimulus. The stroop effect results because people are more trained at word reading than naming colours. Word reading, becomes automatic, while naming the colour of an object takes voluntary effort (Cattell, 1886). Many studies supports this, and have found that word reading is faster than colour naming (Glaser & Glaser, 1982).

The observation made by J.R. Stroop in 1935 have made an extensive impact on cognitive research based on attention. Mostly because the effect is scientifically reliable and easy to replicate (MacLeod, 1992). Dalrymple-Alford (1972) found that it is quicker to name the ink of congruent colour words than to name the ink colour of an unrelated word. This is known as Stroop facilitation, even though it were not studied by J.F Stroop himself. Many explanations have been made to clarify the nature of interference and facilitation effects. Dalrymple-Alford found that colour names produce less interference with colour naming when written in congruent words (Dalrymple-Alford, 1972).

Other studies have used keys to respond on the stroop task instead of manual responses. One example of this is Keele (1972). He concluded that irrelevant information contacted memory because the word meaning changed (Keele, 1972).

The horse race model can be explained when people are presented with two dimensions of a stimuli, and the reading process is more automatic and will therefor reach the single channel first as opposed to the naming process. Because of this the reading process would cause interference or facilitation to the naming process. When changing the reading process, or slowing down the the speed of reading (the horse) it can make the process for naming faster (Morton, 1969). This is supported in Fredreick N. Dyer’s article (1971) where he concludes that facilitation was found of colour naming with congruent combinations of words and colours.

The present study presented colour words and neutral