Visual Field Position and Type of Stimuli on the Stroop Effect

VISUAL FIELD POSITION AND TYPE OF STIMULI ON THE STROOP EFFECT

The Effect of Visual Field Position and

Type of Stimuli on the Stroop Effect

Reynold Hicks

University of Tampa

Abstract

An experiment was conducted to test the effect of lateralization and congruency on reaction time to name colors. This was done using a computer program provided by The University of Mississippi. This effect is called the stroop effect. Results showed that it was neither lateralization nor congruency had a significant effect on reaction time, but the interaction of these two variables that created a significant change in the time needed to recognize colors. It is believed that this is due to the different hemispheric functions of the brain. Studies that are similar to this in nature help to better understand how the brain functions and it capabilities.

The Effect of Visual Field Position and Type of Stimuli on the Stroop Effect

Psychologists have been interested in how the human brain works and how stimuli are processed and interpreted. The brain is a highly complex organ that is the center for all our human functions. The more we know about how it works and how efficient the brain is, the better psychologists will be able to analyze human behavior.

The stoop test has been used for many years to investigate how we process information. Laterality is one of the factors in which the stroop test can be used to investigate. Many researchers have examined laterality in the Stroop task. Dyer (1973) showed that presenting the word and the color separately to the left and right fixation did not alter the Stroop effect. Interference and facilitation were still factors (MacLeod, 1991). There are many instances of the left hemisphere showing more interference during this kind of testing. Aine and Harter (1984) studied this same effect and found that activity associated with interference occurs in the left hemisphere, effecting the response time and error-rate measured. Similar results were found in a study conducted by Posner, Walker, Friedrich, and Rafal; (Citedin, Macleod, 1991) they found that the left parietal and frontal lobe may be involved in disengaging attention. Many other variables such as gender, bilingual ness, even handedness have been proven to alter the Stroop effect.

This experiment investigated how visual field position and differing stimuli influenced the reaction time in naming ink colors. Based on the information above and past studies, these hypotheses were formulated. The time to name the ink colors will vary with visual field position. The slowest time should occur when the stimulus appears in the right visual field because of its association with the left side of the brain. The time to name congruent stimuli should be faster then the time to name incongruent stimuli. The time to name ink color will vary with both visual field position and type of stimuli. Time to name ink colors for congruent stimuli should not vary much with visual field but the time to name ink color of incongruent should increase as the stimuli gets color to the right visual field.

Methods

Participants

This study contained a total of fifteen students from the University of Tampa's upper level psychology class. Thirteen of the participants were female and the remaining two were male. In addition to this class thirty six students from other classes were also used in this study.

Materials

I-Mac G3 computers and a program from Old Mississippi University were used to test the lateralized Stroop effect from http://psychexp.olemiss.edu. The name of the actual program was the Lateralized Stroop Experiment. The stimuli used by this program were colors that appeared laterally on a computer screen. Not only did the colors appear laterally but in differing hemispheres on the computer screen. The colors were in the form of written words. For example the word "red" was shown in green font. This was be an example of an incongruent stimulus because the written color word did not agree with the font color shown. An example of a congruent stimuli is be the word "red" in red font.

Design and Procedure

The experiment