Stroop-Type Cognitive Interference, Research Paper Example

Abstract

In 1935 Stroop discovered that participants were slower in naming the color of ink in which words were printed than at naming the color of ink in which the control stimuli were printed. The Strrop effect is a widely known experiment in the demonstration of cognitive interference. The Stroop experiment has been simulated numerous times since Stroop’s initial study. The significant issue involves the amount of response time. This study seeks to create a Stroop type cognitive interference experiment. The study included 14 college student participants. The subjects were observed over three different condition groups: Control Condition, Congruent Color-Word Condition, and Conflicting Color-Word Condition. The study was similar to other Stroop type cognitive interference studies revealing similar results. The results of this study show that of the three condition groups the Congruent Word-Color Condition resulted in the lowest response time as well as the fewest response errors. Conversely, the Conflicting Word-Color Condition resulted in the highest response time as well as the most response errors.

Introduction

The Stroop effect demonstrates interference, or inhibition, in the reaction time of a given task. For instance, when the name of a color is produced in a color that is different from the color represented by the name, the process of identifying the color of the word is lengthier and more inclined to mistakes than when the color of the word matches the name of the color. The Stroop effect is termed after John Ridley Stroop who first printed his experiments and results in 1935 (Stroop, 1935).

In his article, Stroop discusses the recent history of experiments testing interference. Stroop examines the works of several preceding psychologists. For example, Stroop (1935) considers the work of Miinsterberg, who examined the inhibiting effects of variations in normal everyday habits like “opening the door of his room, dipping his pen in ink, and taking his watch out of his pocket” (p. 643). Stroop (1935) also studies the work of Muller and Schumann who revealed through their early studies “that more time was necessary to relearn a series of nonsense syllables if the stimulus syllables had been associated with other syllables in the meantime” (p. 644). Moreover Stroop (1935) also discusses the card sorting experiments of Bergstrom, Brown, Bair, and Culler, which “found that changing the arrangement of compartments into which cards were being sorted produced interference effects” (p. 644). Stroop (1935) mentions “Several studies have been published which were not primarily studies of interference…” (p. 645). His experiments differed from previous work in that his experiments test a pair conflicting stimuli at the same time. “These stimuli are varied in such a manner as to maintain the potency of their interference effect” (Stroop, 1935, p. 647).

In his first experiment Stroop asked participants to read the written color names of the words independently of the color of the ink. Stroop (1935) explains “The instructions were to read as quickly as possible and to leave no errors unconnected” (p. 648). The results of the study indicate that it “took an average of 2.3 seconds longer to read 100 color names printed in colors different from that named by the word than to read the same names printed in black” (Stroop, 1935). From this experiment Stroop (1935) concluded that “The source of the interference is in the materials themselves” (p. 659).

In his second experiment, Stroop (1935) asked participants to say the color of the letters independently of the printed word along with the second stimulus and to also name the color of the squares. For example, if the word “blue” was written in green, the participants would say “green”, and not “blue”. Additionally, when the squares were presented, the subjects were asked to say its color. In this experiment, Stroop discovered that subjects took more time to finish the color reading in the second task than naming the colors of the squares. This delay was not observed in the first experiment.

The third experiment tested participants at various stages of practice in the tasks and stimulus applied during the first and second experiments. Stroop monitored various stages in order to account for the effects of association. Stroop (1935) mentions that the third experiment results reveal “the time score is lowered considerably by practice” (p. 655). Furthermore, Stroop (1935) states that “These results show that practice increases individual differences where a stimulus to which the subjects have an habitual reaction pattern is interfering with reactions to a stimulus for which the subjects do not have an habitual reaction pattern” (p. 658).

Logan and Zbrodoff (1998) review “Four experiments examined the Stroop effect with typewritten responses. Experiment 1 compared vocal, arbitrary-keypress, and typewritten responses and found the largest Stroop effect for typewritten responses” (p. 978). Additionally, Logan and Zbrodoff (1998) comment that “this experiment demonstrated a Stroop effect with typewritten responses, which is important because it has not been demonstrated before” (p. 983).

MacLeod (1991) reviews “the literature on interference in the Stroop Color-Word Task, covering over 50 years and some 400 studies” (p. 163). The article summarizes different theoretical positions including relative speed of processing and automaticity of reading. MacLeod (1991) states that “recent theories placing the explanatory weight on parallel processing of the irrelevant and the relevant dimensions are likely to be more successful than are earlier theories attempting to locate a single bottleneck in attention” (p. 163).

Methods

This particular study examined 14 participants all together. All of the selected participants were undergraduate psychology students from XYZ University. The participants ranged in age from 19 to 28 years old with a median age of 22.4 years. Of the selected participants, eight were male and six were female. The students received course credit for their participation in the study.

The participants were not English as second language (ESL) students. English served as the primary language spoken by each of the participants. Additionally, every participant reported normal or corrected-to-normal vision.

A standard insert type of computer computer system was used in the experiment. The computer included a keyboard and screen dimensions monitor with a resolution of resolution. The computer used for the study was situated on a private and secluded table in a quiet and well-lit room. The computer contained name of computer software software for the purpose of generating stimuli as well as measuring and reporting response variables from the participants.

An unmeasured practice condition was conducted before the measured control and experimental conditions. Please briefly explain this practice condition

The study introduced color-word stimuli in congruent and conflicting forms. Words were presented in the colors red, green, blue, and yellow. The congruent color-word stimuli presented color names typed in the matching color (for example the word red was displayed in red typeface). Conversely, the conflicting color-word stimuli displayed color names typed in a different color (for example, the word red was displayed in blue typeface instead of red typeface). Variation was displayed on the monitor.

The Control Condition consisted of a 24-trial display of solid colored rectangles. The rectangles were presented in the colors, red, green, blue, and yellow and measured insert size of the rectangles. The Congruent Condition followed the control condition with a 24-trial congruent color-word experiment. And finally, The Conflicting Condition displayed a 24-trial conflicting color-word experiment.

The participants responded to the stimuli by selecting a corresponding key on the keyboard. For example, for a response of red, participants would push the R key on the keyboard; for a response of green, participants would push the G key on the keyboard, and so on. An unmeasured test, referred to as the practice condition, preceded the measured control and subsequent experimental conditions. Following the stimuli-response measurement across the control and experimental conditions, the software compiled the results of response time (measured in seconds) to the stimuli and the number of response errors.

Results

The measure of results across the three experimental conditions consisted of: response time (RT) (see Figure 1) measured in seconds and number of response errors (see Table 1). In this within-subjects study, all participants individually completed each series of trials across the three levels of test conditions. Response times in the Control Condition were (M=28.29 sec., SD=3.05). Following the Control Condition, the experimental Congruent Word-Color Condition resulted in lower overall response times. Response times in the Congruent Word-Color Condition were (M=25.93 sec., SD=1.96). The highest response time was represented in the Conflicting Word-Color Condition. Response times in the Conflicting Word-Color Condition were (M=36.80 sec., SD=3.52).

The Control Condition errors measured (M=1.21, SD=0.80). The Congruent Word-Color Condition response errors were lower than the response errors represented in the Control Condition. The Congruent Word-Color Condition response errors were (M=0.71, SD=0.73). The highest number of response errors was shown in the Conflicting Word-Color Condition. The number of response errors in the Conflicting Word-Color Condition were (M=2.71, SD=1.33).

Of the three condition groups the Congruent Word-Color Condition resulted in the lowest response time as well as the fewest response errors. Conversely, the Conflicting Word-Color Condition resulted in the highest response time as well as the most response errors.

Discussion

This study evaluated the amount of time in which subjects took to respond to three different conditions. The condition groups observed in this experiment were the Control Condition, Congruent Color-Word Condition, and Conflicting Color-Word Condition. The experiment conducted by Stroop, along with many similar studies that have followed, implemented vocal responses to conditions, meaning that the participants verbally expressed the color names out loud. However, many other studies (as the one presented in this paper) implemented arbitrary-keypress responses in which participants pushed keys on a keyboard that represented color names. The literature revealed that the Stroop effect has been discovered across both verbal and keypress responses.

This study revealed that participants took longer to respond to Conflicting Color-Word Conditions than Control Conditions and Congruent Color-Word Conditions. Additionally, more errors were reported in the Conflicting Color-Word Condition than the Control Condition and the Congruent Color-Word Condition.

The study was similar to others Stroop effect studies that have been conducted over the years. Furthermore, this study revealed comparable results as well. In many studies, the Conflicting Color-Word Condition results in the slowest response times with the highest amount of errors.

An important note is that many studies which compared response modalities often discovered a stronger Stroop type cognitive interference among vocal responses than with keypress responses. However, some studies revealed “no difference between response modalities in the magnitude of the effect” (Logan & Zbrodoff, 1998). This study represents data collected from only keypress responses. The results of the study may have been different and more solid and reliable with verbal responses in addition to the keypress responses. Further research should implement both response modalities. Nonetheless, the study is relevant to the field in solidifying the Stroop effect and adding significant variations between conditions.

References

Akiva-Kabiri, L., & Henik, A. (2012). A Unique Asymmetrical Stroop Effect in Absolute Pitch Possessors. Experimental Psychology , 272–278.

Chajut, E., Mama, Y., Levy, L., & Algom, D. (2010). Avoiding the Approach Trap: A Response Bias Theory of the Emotional Stroop Effect. Journal of Experimental Psychology, 1567-1572.

Heine, A., Tamm, S., Smedt, B. D., Schneider, M., Thaler, V., Torbeyns, J., Jacobs, A. (2010). The Numerical Stroop Effect in Primary School Children: A Comparison of Low, Normal, and High Achievers. Child Neuropsychology, 461–477.

Logan, G. D., & Zbrodoff, N. J. (1998). Stroop-Type Interference: Congruity Effects in Color Naming With Typewritten Responses. Journal of Experimental Psychology, 978-992.

MacLeod, C. M. (1991). Half a Century of Research on the Stroop Effect: An Integrative Review. Psychological Bulletin, 163-203.

Stroop, J. R. (1935). Studies of Interference in Serialverbal Reactions. Journal of Experimental Psychology, 643-662.