Experimental Psychology Stroop Effect Essay

The research assessed in this article discusses the Stroop effect. The Stroop effect occurs when our selective attention fails and we are unable to attend to some information and ignore the rest. This study tests the Stroop effect by presenting the participant with a congruent or incongruent word and the participant is asked to type the color of the word or the actual word in a series of trials. In this research, it has been found that participants had faster reaction times for congruent items and slower reaction times for incongruent items. In addition, participants had faster reaction times when asked to type the word and slower reaction times when asked to type the color. Racing Horses and the Stroop Effect We have the ability to attend to the things we’re looking for; however, sometimes this ability of selective attention becomes compromised. Where’s Waldo is a game that tests one’s ability to selectively attend to a stimuli; you must find Waldo in an overly crowded picture that attempts to hide him. If one’s selective attention becomes compromised, one would either not be able to locate Waldo or would take a long amount of time to locate Waldo. We can study this phenomenon of selective attention via the Stroop effect. According to J. R Stroop, â€Å"it takes more time to name colors than to read color names (1935). † In addition, it is faster to name the color for congruent items than incongruent items. Congruent items include items such the word â€Å"red† in the color red; incongruent items include items such as the word â€Å"blue† in red ink. In a basic Stroop experiment, participants are provided with a list of congruent words and a list of incongruent words and are asked to name the color of the word or the actual word itself. Having a big Stroop effect indicates that one’s selective attention has failed. In Stroop’s original version of the experiment, results demonstrated that when participants were asked to name the color of the ink of an incongruent item, there was an increase in ink naming time. However, when the participants were asked to name the word, incongruence of the ink to the word did not have an effect on the amount of time it took to read it (Dunbar & MacLeod, 1984). In Kevin Dunbar & Colin M. MacLeod’s paper, they refer to what is known as the horse race model (1984). This horse race model attempts to explain the Stroop phenomenon as a race between two responses. The first response, which always seems to win the race, is the response to the word; the second response is the one to the color of the ink. The horse race model states that color naming is slower than word naming because words and colors have different processing times; when the faster process finishes, it’s result can interfere with the slower process. â€Å"The simplest hypothesis, consistent with all the evidence, is that the interference occurs after naming (Morton & Chambers, 1973). Words interfere strongly with color naming; in an incongruent trial, one identifies the word first, the identification of color of the word only comes later and there is a need to overcome the incorrect response, which causes a slight delay in response time. The purpose of this experiment is to further test the horse race model of the Stroop effect. In this experiment, the two independent variables are congruency, whether the items are congruent or incongruent, and task, participants will be asked to name the color of the item or the word. Results will be measured by how long it takes participants to respond in each condition. There are several predictions made about this replication of the Stroop experiment: firstly, we predict that there will be a main effect of congruency; we expect an overall Stroop effect. Secondly, we predict that there will be a main effect of task; we expect that participants should be faster to type words than colors. Finally, we predict an interaction between congruency and task; we expect that the Stroop effect will be larger for typing colors than for typing words. Method Participants Twenty-one undergraduate, male and female students were recruited from an experimental lab class at the City University of New York Brooklyn College. Materials and Design In this within subjects design, we used a 2 (Congruency: Congruent vs. Incongruent) x 2 (Task Type: Naming color vs. Naming word) factorial; the dependent variable measured was reaction time. The stimuli were presented on a seventeen inch computer monitor and participants were given a standard keyboard for their responses. The stimuli used were four words: red, green, blue, yellow; and four colors: red, green, blue, yellow. For the independent variable of congruency, there were four possible congruent items and twelve possible incongruent items. For the independent variable of task, there was one block of forty-eight trials asking the participant to type the word and one block of forty-eight trials asking the participant to type the color. The order of each block was randomly determined by the computer for each participant. Half of the participants did the word naming then color naming; the other half did color naming then word naming. Each trial begins with the presentation of a fixation cross in the center of the screen, visible for 500 milliseconds. The fixation cross is removed and immediately followed by the word and color stimulus; this stimulus remained on the screen until a response was typed and the participant pressed the spacebar key. There are four possible responses: red, green, blue, and yellow. Responses are given by having the participants type the word into the keyboard. Immediately after the response, the stimuli were removed from the screen and the next trial appeared 500 milliseconds after the participant pressed the spacebar. Procedure Participants were given instructions by the experimenter, separated into groups, and sent randomly to different rooms which held the computers they would be using for this experiment. Each participant was given a total of ninety-six trials; there was one block of forty-eight trials asking the participant to type the word and one block of forty-eight trials asking the participant to type the color. The order of each block was randomly determined by the computer for each participant. Half of the participants did the word naming then color naming; the other half did color naming then word naming. The participants were prompted to read the instructions on the screen and enter their initials prior to starting the experiment. Once the experiment begins, there is a fixation cross displayed for 500 milliseconds. Following the fixation cross, the task cue and stimuli were displayed at the same time until the participant responded. After the participant responded and pressed the spacebar key, they were prompted with another trial. After each participant completed the experiment they were instructed to return to the classroom where they were debriefed by the experimenter and allowed to leave. Results The results of this experiment are presented in Figure 1. The mean for the naming color/congruent condition is 1044. 57ms; the mean for the naming color/incongruent condition is 1210. 62 ms; the mean for the naming word/congruent condition is 838. 05 ms; and the mean for the naming word/incongruent condition is 862. 24 ms. The mean reaction times (RTs) from each condition were submitted to a 2 (Task type: name word vs. name color) x 2 (Congruency: congruent vs. incongruent) within-subjects ANOVA. The main effect for task was significant, F(1,20) = 62. 48, MSE = 1616576. 0, p < 0. 05; this shows that participants had a faster RT when asked to name the word (M = 850. 14 ms) as opposed to when asked to name the color (M = 1127. 60 ms). Mean RTs were faster for word than color naming. In addition to a main effect of task, there is a significant main effect of congruency, F(1,20) = 22. 65, MSE = 190000. 30, p < 0. 05; this illustrates that participants had a faster RT when the items were congruent (M = 941. 31 ms) than when the items were incongruent (M = 1036. 43 ms) Mean RTs were faster for congruent items than incongruent items. Finally, we found a ignificant interaction between congruency and task type, F(1,20) = 42. 43, MSE = 105648. 11, p < 0. 05; this interaction demonstrates that there is a greater difference between the means of congruent and incongruent items when asked to name color than there is between the means of congruent and incongruent items when asked to name the word. Discussion We predicted a main effect of congruency which is, in fact, what we see from our results. We see this main effect due to the Stroop effect, which states that it is faster to name the color for congruent items than incongruent items. In addition, we expected to see a main effect of task type and that the word task will produce faster RTs than the color task; which is precisely what we have found. We can explain this finding with the theories of the horse race model. It has been found, through earlier research, that reading words is a faster process than color naming because reading is an automatic process (Dunbar & MacLeod, 1984). We predicted to see that naming the color will intensify the Stroop effect whereas naming the word will minimize the Stroop effect; we have found exactly this in our results. These outcomes can be explained with the horse race model as well. The horse race model assumes two things: first, words and colors have different processing times; color naming is slower than word naming. Second, the Stroop effect is asymmetrical: when the faster process is finished, the result of that process can interfere with the slower process. Words interfere strongly with color naming; however, colors interfere weakly with word naming. MacLeod’s (1991) study explained: This speed difference is seen as particularly critical when two potential responses (e. g. , one from a word and one from an ink color) compete to be the response actually produced. The time cost of this competition is â€Å"interference. This general interpretation is referred to as response competition occurring at the end of a horse race, because the two codes are seen as racing to control final output. (p. 187) One of the flaws of this experiment is that it is possible that not all participants are proficient in the placement of keys on a computer keyboard; this would affect the reaction time for theses participants as they would need extra time to find the keys. Another flaw is that we didn’t take into account typing errors and the program used did not record error rate. This could mean that we have not successfully measured one of the items we attempted to measure. We attempted to see if there was a difference in processing time between the task of naming the word and the task of naming the color. Since we did not take into account typing errors and error rate, it is possible that a participant could have responded quickly with an incorrect response and therefore caused the RT time to be quicker. The greatest defect of this experiment is the sample size, 21 participants. In future studies it is recommended that this experiment be run with at least 30 participants who can comfortably recognize the keys on a standard computer keyboard. In addition to a larger sample size, perhaps changing the colors and the names of colors (from red, green, blue, and yellow to, for example, pink, purple, orange, grey) would yield a smaller or larger Stroop effect. Another change that can be experimented with is age. MacLeod (1991) references a study done by Lund (1927) which finds that â€Å"children younger than reading age were faster on color naming than word reading. † Perhaps there may be difference between children that are younger than reading age, children who have just recently learned the alphabet, and/or children who just recently learned to read. Also, could there be a difference between children, adolescents, middle-age, and/or old-age? MacLeod (1991) also references a study conducted by Ligon (1932) that tested the â€Å"differential-practice concept† in children between the ages of about 5-14. Ligon found that practice and training did improve RTs for both color naming and word naming tasks, however, â€Å"the difference between the skills remained unchanged. † A final suggestion for future research would pose this question: would we find similar results if ran such a study with adults?