The Stroop Effect in College Students

The Stroop Effect studied in this experiment is the interference that happens when processing one dimension of a complex stimulus while ignoring other dimensions. We tested this effect by having our subjects read through a list of forty-eight names of colors – each printed in a different color then the word. The study suggests that reading is an automatic process and verbal material provides interference. This means that it is difficult to ignore the names of the colors and just say the colors of ink of each name. The left hemisphere primarily does verbal functions and the right hemisphere primarily does non-verbal functions. This effect requires use of both hemispheres, which is more cognitively complex and requires more time to process.

The Stroop Effect in College Students

Stroop (1938) found that subjects required considerably more time to name colors when the colors were presented in the names of conflicting colors. For example, if the word BLUE was printed in green ink, identifying the ink color (green) took more time than identifying the ink color if the word was consistent (GREEN). As a result, the Stroop effect has been defined as the interference that occurs when processing one dimension of a complex stimulus while ignoring other dimensions. There are few psychological phenomena that have received as much empirical research attention as the Stroop effect. In fact, MacLeod (1991) provided an integrative review of over 50 years of research on the Stroop effect. Studies have investigated the causes of the effect (Dyer, 1971a; Hintzman, Capre, Eskridge, Owens, Shaff, & Sparks, 1972; Nealis, 1973; Wheeler, 1977) the differential effects across various groups (Das, 1970; Dyer, 1971b; Golden, 1974) and the multiple uses of a Stroop test in diagnostic settings (Dyer, 1973; Golden, 1976).

Theoretical Explanations

The Stroop effect is hypothesized to result from several cognitive and physiological factors. Nealis (1973) and Wheeler (1977) proposed that the Stroop effect occurs as a result of the interference that occurs when two possible responses compete. In Stroop scenarios, participants are shown stimuli that may contain one or two sets of information to process. When a complex stimulus (i.e., one containing both verbal and color information) is displayed, participants must attend to and identify one dimension of the stimulus while ignoring the other dimension. When such selective attention is required, some stimuli provide greater interference than others do. Previous studies have suggested that reading is a relatively automatic process. If reading does occur automatically, verbal material may provide more interference because of the difficulty in ignoring it.

A potential physiological explanation for the Stroop effect is related to the lateralization of certain cognitive functions to different hemispheres of the brain. In Stroop scenarios, the stimuli presented may contain both verbal and color information. Research on hemispheric specialization has supported the notion that verbal functions (including language, speech, and writing) tend to be localized in the left hemisphere and non-verbal functions (spatial problems, music, art, and color distinction) tend to be localized in the right hemisphere (Corballis, 1991). If an identification task involves functions tapping both hemispheres, it is more cognitively complex and thus requires more time to process.

Tests and Applications

The Stroop effect has been found to affect various demographic groups differently. Das (1970) studied changes in Stroop test responses as a function of mental age and Dyer (1971) studied differences in monolinguals and bilinguals. Golden (1974) investigated gender differences and found females’ performance on color-identification trials to be faster than males. However, measures of interference were not significantly across gender groups.

The Stroop test has also been used for diagnostic purposes. Dyer (1973) outlined how the Stroop phenomenon has been used to study various perceptual and cognitive processes. Golden (1976) also discussed how the Stroop test has been used to diagnose brain damage.

The Present Study

Although the Stroop effect has been studied extensively, questions remain. The first intent of this study is to show that it takes more time to process complex tasks that use both hemispheres of the brain, rather then simple tasks that only use one hemisphere of the brain. The second intent of this study is to show that there is little difference in scores between males and females.



In this study, we measured the Stroop Effect on students in Dr. Peter Bachiochi’s PSY100: General Psychology class at Eastern Connecticut State University. The class meets Tuesdays and Thursdays from 2:00pm-3:15pm participated in the experiment. The class consists of forty students. Twenty-one students are female (52.5%) and nineteen students are male (47.5%). Most students are between the ages of eighteen and twenty-one. Students were required to participate in the experiment. They were told a few days in advance not to miss this particular class because it would relate to the Psychology paper that is required for the class. The class was broken up into groups of four or five. There were four trials and three cards. Each person in the group went through the four trials. When the person was done, the next person in the group wet through the trials but the trials were counter-balanced. Counter-balanced means that each person went through the trials in a different order because if they all went through them in the same order it would be likely that the scores would get better after each person went. If the scores did this, it would mean that others in the group had learned the names of the colors and it would skew the results. All trials were performed with all students so if any students in the class had a learning disability or reading problem, it would somewhat affect the class average.


Items used include four cards, a stopwatch or clock with second hand, and paper and pen to record data collected.


The independent variable was the type of stimuli involved. The two types of stimuli are the color blocks (patches) and the color words printed in incongruent colors. The dependent variable was the length of time it takes to name the colors. Time is a common dependent variable and is a good index to show how hard/easy it is to process tasks. . In most experiments there is an experimental group and a control group and the control group is a baseline for comparison but for this experiment, the group of subjects serve as their own control group. The experimental condition in the experiment was the task in which the stimulus materials were color words printed in incongruent colors. The control condition in the experiment was the color patches.


Card number one was a sheet with forty-eight names of colors. Each subject had to read off the list of colors. One person in the group timed each subject and wrote down the time it took him or her to do the trial. In Card number two; each subject had to say aloud the forty-eight color names of ink color blocks on the paper. On card number three; each subject had to read the names of the forty-eight colors. Each color name was in a different color ink. For example, if the word RED was printed in blue ink, identifying the ink color (blue) took more time than identifying the ink color if the word was consistent (BLUE). The subject had to use card number three again and say the color of ink each word was.


The following results table illustrates the seconds (when averaged together) it took for both males and females to perform each trial. The deviation between males and females for each trial is illustrated as well as the comparison between trials one and three, trials one and two, trials two and four, and trials two and three. The chart shows that on average there is not much of a difference between the male and female scores. However, there is a big difference when comparing the results of trials one and three together (word trial and mixed word trial) and Trials two and four together (color trial and mixed color trial). The data shows that there is a relationship between gender and the hemisphere of the brain: males are more likely to think quicker in the left hemisphere (language, speech, and writing), in other words better at verbal skills, and females are more likely to think quicker in the right hemisphere (spatial problems, music, art, and color distinction), in other words at non-verbal skills. The results of both the deviation of trial one and three, both word trials, show males on average doing better then females and the results of both the deviation of trial two and four, both color trials, show females on average doing better then males.

Table 1: Stroop Test Results in number of seconds
Trial #, name, deviation Males (average) Females (average) Deviation between Males & Females
Trial 1: Word 17.6 16.8 0.8;
Males higher avg.
Trial 2: Color 23.0 23.3 0.3;
Females higher avg.
Trial 3: Mixed Word 20.1 19.6 0.5;
Males higher avg.
Trial 4: Mixed Color 38.3 41.5 3.2;
Females higher avg.
Deviation between Trials 1 & 3 2.5
Trial 3; higher avg. 2.8
Trial 3; higher avg. .3;
Females higher avg.
Deviation between Trials 1 & 2 5.4
Trial 2; higher avg. 6.5
Trial 2; higher avg. 1.1;
Females higher avg.
Deviation between
Trials 2 & 4 15.3
Trial 4; higher avg. 18.2
Trial 4; higher avg. 2.9;
Females higher avg.
Deviation between
Trials 2 & 3 2.9
Trial 2; higher avg. 3.7
Trial 2; higher avg. 0.8;
Females higher avg.


My hypotheses were supported by the data collected in the experiment. The experiment results helped to determine differences of results due to gender and due to the trial and the kind of trial it was. It took more time to identify the colors on trial 2 then the words on trial 1 for both genders. This is because even though both involve simple tasks it takes more time to perform non-verbal functions (spatial problems, music, art, and color distinction) with the right hemisphere then it does with verbal functions (language, speech, and writing) with the left hemisphere of the brain.

It takes more time to process information that requires both the left and right hemispheres of the brain. Verbal skills use the left hemisphere and non-verbal skills use the right hemisphere. Color distinction uses the non-verbal hemisphere, which is also the left hemisphere. It has been proven in past experiments that more males have difficulties with distinguishing colors and more males are color-blind then females. The experiment results indicate that it is more difficult to identify information in a complex stimulus as opposed to information in a simple stimulus.

Some of the problems with the experiment were that all groups were doing the experiment at the same time in the same room. Groups could easily hear other groups and simply by hearing other groups, subjects could have been distracted and subjects who went first didn’t have the opportunity to hear other people in their group as well as people in other groups.

Subjects who went last could have “learned” the material. If the experiment was repeated, groups should go off by themselves. If the results of this study needed to be exact then the same stopwatch or clock should be used for all trials to ensure better accuracy. Also, an anonymous survey should have gone around before the experiment asking people if they had a learning disability or a reading disability. Other questions could include if the subject is in good health, good emotional state, whether the subject is hungry or thirsty, whether the subject is stressed, etc. The survey could be made to be yes and no questions. Of course, you can’t find subjects that are “perfect” but knowing factors that could influence the results may help in justifying why results may be different by quite a bit if the experiment were to be repeated. Other things that the survey should ask is whether the student is monolingual or bilingual, and what demographic group he or she belongs to.

It can be concluded when looking at the results of the Stroop test, we have an easier time doing one task at a time and if we try to do two things at once there will be a slower reaction time. This could be a correlation into the fact why many states prohibit drivers from using their cellular phones when they are operating their vehicle. Companies who require their employees to do more than one task at one time may have lower productivity then companies who have their employees finish a task before starting a new one. Students may find it more difficult to work on homework of one subject partway and then work on homework in another subject partway. It might be more effective if students concentrated on one task until it was finished and then went to another. The test also shows that we can be easily distracted – maybe students shouldn’t listen to music while trying to write an essay because both hemispheres of their brain are trying to react at the same time causing less reaction time and less productivity. This also may explain why it is difficult to talk on the phone while writing e-mail or any other piece of writing. Also, maybe both students and employees have slower reaction time when they are under heavy deadlines. It would be quite interesting to compare the Stroop reports and results our class had with other PSY 100 classes who underwent the same experiment.

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