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 had a 3×2 design with two independent variables. The first independent variable was visual field position.
The words appeared to the right, left, or middle of the field of vision established by a pulsating focal point used to initiate each trial The second independent variable was the type of stimuli (congruent or non-congruent). The appearance and screen location for each trial is randomly assigned. The dependent variable was the reaction time it takes to submit a response.
The dependent variable (response time) was calculated by the time between a word’s appearance and a key press that indicated the font color of the stimulus into the computer. ” represents the color red, “4” represents blue, “6” represents green, and “8” represents yellow. First the website http://psychex. olemiss. edu was connected to via the internet. After an in depth overview of the experiment is read by the participants, each will have to agree to a consent form. Then practice for the experiment is begun. This practice helps the participants to become familiar with the number- color codes that are necessary for the program to record the reaction time of each response.
After the practice trials are completed and proficiency is proven, a number-color code is acquired the actual experiment can be conducted. The participants elected to complete 72 trials. A correct trial run was recorded and admissible for inclusion in the PsychExps database if it was correct. Each trial begins with a pulsation plus sign that serves to establish a focal point on the computer screen. Research participants press a key when they are ready for a word to be presented. Next there is a delay of 1 to 3 seconds before the word appears.
When the words appear they are written vertically on the screen. The central axis of the word is designed to be approximately 3 degrees of visual angle to the right or left of the fixation point on lateral presentations, though the actual visual angle will vary depending on monitor size and the distance of research participants from the monitor. This should be a constant in the experiment with each participant about 11 inches from the monitor and a standard size monitor. On the central presentation, the word axis is at 0 degrees relative to the fixation point.
Display times are fixed at 150 msec to assure that laterally presented words are experienced in a single visual hemisphere. With four words (red, blue, Green, and yellow) that are printed in a word-color congruent form or non-congruent form appearing at any of three positions (right, left, or center), there are 24 possible stimulus events. The reaction time type of stimuli is measured and recorded for each trial. After the experiment is completed the result must be printed out and analyzed.
