The Stroop Effect Experiment: How Our Brains Process Information

Abstract

The Stroop effect occurs when there is a delay due to the processing of different types of information. The purpose of the experiment was to investigate the Stroop effect and to examine the difference in congruent and incongruent information. The investigation was carried out with the participants conducting the Stroop test for the neutral, incongruent, and neutral images. The reaction times for the given tests were analyzed. The hypothesis of the study was that there would be a difference in the reaction times for the three different conditions. The findings showed that the three conditions (congruent, incongruent, and neutral conditions) had different reaction times where the congruent images had a short reaction time, the neutral image had a longer reaction time compared to the congruent image, and the incongruent image had a longer reaction time. The conclusion from the study was that there was a delay between the congruent processing of information and the incongruent one.

Stroop Effect Experiment

The Stroop effect is a method that is used to study selective attention and the processing of information as shown by human beings. The test is usually conducted by participants that view words printed with similar colors with meaning of the words and other words that have different colors from the meaning of the words. Words that have similar colors to the meaning of the words are described as congruent condition while words that have different colors from the meaning of the words can be described as incongruent condition. The neutral condition occurs when the symbols and shapes are used to present the colors. The participant is usually presented with the colors and the words or responsible and is then required to choose the correct one. The difference in the reaction times from the Stroop experiment can be attributed to the conflicting reaction when the stimuli is congruent as compared to when the stimuli is incongruent. The hypothesis for the study was that there would be a difference in the reaction times when the participants were presented with the congruent, incongruent, and neutral conditions. It was expected that the neutral condition would have the shortest reaction time, followed by the neutral condition that would have a longer reaction time, and the incongruent condition would have the longest reaction time.

The Stroop Experiment was introduced by John Ridley Stroop who used the Stroop experiment in his psychology work to test human cognition. Stroop conducted the experiment by using black ink to write the name of colors. He then used different colors to write some of the words and then used squares to show the colors. The results of the experiment revealed that the participants took longer to read the colors and words that had different colors compared to words that primarily used black or the square symbol. Stroop (1935) observed that reading words required a dominant response for the naming since there was a significant competition from the name of the words compared to the colors of the words. The result of the experiment has since been adopted referred to as the Stroop effect.

Previous studies have also been developed to confirm the Stroop Effect. Musen and Squire (1993) conducted the Stroop experiment and established that there is a difference in people’s concentration and attention for the different conditions. He argued that the memory plays a big role in enhancing people’s attention and instances that have distractors can reduce the functioning of the memory. The Stroop effect has been applied to understand the social perception process. According to Ross et al. (1977), there can be biased perceptions in the response to certain questions. The biasing effects of the questioner and answerer can be compared to the Stroop effect where previous memory creates a bias that causes the Stroop effect and a delay in one’s response.

Method 

Participants 

There were 15 research participants that took part in the study. The participants were selected randomly from an experimental psychology research program. No participant was compensated for the given experiment. They went through three different types of testing sessions including the congruent session, incongruent session, and the neutral session. The first testing session involved being assigned words that had the corresponding colors i.e. congruent conditions. For instance, the word ‘RED’ was painted with a red color. The four different colors that were used in the study were red, green, blue, and yellow. The second testing session involved the participants being assigned words that had different colors. For instance, the word ‘RED’ could be painted with the other colors like the green, blue, and yellow but not the red one. The third testing session involved the participants being given a neutral condition through the use of XXXXs. For instance, a red color was used to display the XXXXs symbols and the participants were asked to identify the color. The participants went through a total of twenty tests for each of the testing session.

Design 

The design of the experiment was a within-subjects ANOVA design with three conditions. A within-subjects design was applied since there were three measures obtained from the participants. Additionally, all the participants went through all the experiment conditions. The independent variables for the experiment was the Stroop test condition i.e. congruent, incongruent, and neutral. The conditions were measured by considering the type of test applied. The dependent variable was reaction times. It was measured by considering the time interval between the display of the color and the selection of the color. The given conditions and the reaction times were automatically generated by the online application used to conduct the experiment. There was a total of 20 trials per condition.

Procedure 

The participants were recruited from the experimental psychology research program. The took part in the study voluntarily. Before starting the experiment, they were given instructions that provided information about how the experiment would be conducted. They were informed that the experiment was used to measure their accuracy and the reaction times for the different conditions. The participants were then given a link that was used to access the Stroop test and conduct the experiment. The colors included in the experiment were the color red, green, blue, and yellow. The total amount of time that the participants committed in the study was approximately ten minutes where they spent a maximum of three minutes for each of the condition. After the completion of the completion of the study in about ten minutes, the participants were thanked for their participation in the experiment.

Statistical Analysis 

The first statistical test used to conduct the experiment was a descriptive statistic where the means and standard deviations (SDs) for the reaction times were evaluated. A graph was populated to show the difference in the reaction times between the congruent and incongruent data. The repeated measures ANOVA test was used to test whether the difference in means in the reaction times for the different conditions was significant. Additionally, the Post Hoc Turkey test was used to identify whether the difference within the specific groups was significant.

Results 

The initial prediction was that there would be a significant difference in at least two of the three conditions. The result from the one-way repeated measures ANOVA showed that mean reaction times for the different conditions was statistically significant (F (2,43) = 22.2 and P<0.001). We reject the null hypothesis and accept the prediction. The second prediction was that there would be a difference in the means within the groups. To investigate the second hypothesis, the post-hoc analysis showed that incongruent and congruent condition and the incongruent and neutral were statistically different from each other (congruent – incongruent p<0.001 and incongruent – neutral p<0.001). However, the congruent and neutral conditions were not statistically different (congruent-neutral p = 0.896). The congruent condition showed a smaller reaction time (M = 1321ms) compared to the incongruent condition (M = 1798ms) and the neutral condition also had a smaller reaction time (M = 1283ms).

Discussion 

The results of the study were similar to the previous findings on the Stroop effect. The objective of the study was to investigate the Stroop effect and to show the difference between congruent and incongruent processing of information. The results revealed that there was a difference in the reaction times between the two conditions. The results are similar to past research that established that reading words was a dominant and automatic response compared to identifying the colors of the words. The implication of the study is that there can be different factors that can impact the processing of information. Automatic processing of information can be used to further enhance formation of habits, learning skills, and multitasking ability. Automatic activities are easy to replicate and have a smaller delay.

The limitation of the study was that there were limited neutral conditions, poor control in the color of words, and the possibility of Stroop interference. The Stroop interference occurs after conducting the experiment multiple times until there is a small difference in the reaction times for the given conditions. Future study should explore more conditions and could analyze the impact that Stroop interference can have on the outcome of the experiment.

Conclusion 

The study examined the Stroop effect and showed that there is a difference between the congruent and incongruent response to information. The congruent and neutral conditions had the shortest reaction times while the incongruent condition had the longest reaction times. The difference in the processing of information can be used to explain automatic and non-automatic response and analyze the formation of habits. Future study can further analyze more conditions, strive to establish better control of the conditions, and examine the Stroop interference.

References 

Musen, G., & Squire, L. R. (1993). Implicit learning of color-word associations using a Stroop paradigm.  Journal of Experimental Psychology: Learning, Memory, and Cognition ,  19 (4), 789.

Ross, L. D., Amabile, T. M., & Steinmetz, J. L. (1977). Social roles, social control, and biases in social-perception processes.  Journal of personality and social psychology ,  35 (7), 485.

Stroop, J. R. (1935). Studies of interference in serial verbal reactions.  Journal of experimental psychology ,  18 (6), 643.