Replication of the Stroop Effect Experiment - Research Paper Example

? Replication of the Stroop Effect Experiment Introduction Every individual is aware of events where information that is similar to that which is being actively processed interferes with cognitive processes. The most famous experiment that explores such interference was conducted by John Ridley Stroop (Stroop, 1935). The study found evidence for a robust phenomenon that reveals how difficult it can be to focus on one and ignore another among two closely related stimuli. This effect has since been named the Stroop effect. In the classic demonstration of the Stroop effect, words (names of colors) are presented to the participant in colored ink; and the participant is required to ignore the word and name the ink color. When the ink and word are consistent, (e.g. the word 'red' written in red ink), responses are generally quick. However, when the ink and word are inconsistent (e.g. the word 'red' written in green ink), responses are relatively slower. The Stroop effect expects that the meaning of the words presented will interfere with the color naming task in the incongruent condition (Sternberg & Mio, 2009). Stroop (1935) found strong and consistent evidence for this effect. His study reported that a subject's ability to read words was influenced by the color in which the words were printed (Sternberg & Mio, 2009). Likewise, the subject's ability to name the ink colors was influenced by the actual words as well. In fact, each task, naming colors and reading words, received interference from stimuli associated with the other task. The original study checked for three phenomena. The Effect of Interfering Color Stimuli Upon Reading Names of Colors Serially The Effect of Interfering Word Stimuli upon Naming Colors Serially The Effects of Practice upon Interference (Galotti, 2009) The interference of color stimuli upon reading words was calculated as the difference in the time for reading the words printed in colors and the same words printed in black. The difference in the time for naming the colors in which the words are printed and the same colors printed in squares (or swastikas) was taken as the measure of the interference of conflicting word stimuli upon naming colors. Colors interfered less with reading exercises as compared to the interference of words on color naming. Stroop (1935) also found some evidence for gender differences and reduction in interference as a function of practice. Practice was associated with higher response speeds across stimuli. Practice also allowed the individual difference among participants be become observable, leading to the conclusion that individual differences did play an important role in the reaction times noted for different participants (Galotti, 2009; Balota & Marsh, 2004). Automaticity in reading Children take several years to master the skill of reading fluently. But with years of practice, reading becomes an automatic response and in adults, reading words is faster and more automatic than color naming. Skills that are highly practiced become automatic and can be carried out with little or no mental effort (Galotti, 2009). Reading is basically an example of over learning. The Stroop effect occurs when people attempt to name the ink – color of words that spell out a conflicting color. Even though the task requires a color naming response, people experience a competing response tendency to read the words. Because reading is so highly practiced, it is hard to suppress the spelled-out word and report only the color name (Galotti, 2009). It can thus be concluded that responding was faster in conditions involving only one response tendency, slower in the cases where two or more would be needed between responses. Explanations for the Stroop effect Garrett and Lemmon (1924; in Underwood, 1993) believe that the interference effects which arise in naming colors are due not so much to an equal readiness of the color names as to an equal readiness of the color recognition processes. The strength of the associations between colors and their names also affects interference. Posner and Snyder (in Underwood, 1993) provide an important follow-up to the Stroop paper and explore the distinction between automatic processes (which we have little or no control over) and attentional processes (which we clearly control). They have found that even for highly practiced subjects, it is not possible to completely eliminate the interference of the incongruent words. Kelle (1973; in Underwood, 1993) demonstrated the importance of output interference by showing that non-color words produce less interference than the color words. This is because there is higher semantic association between the required output and color words, and lesser between the non-color words and the required output. Tipper (1992; in Underwood, 1993) has addressed the question about what happens to the non-selected information during the selection task in the Stroop condition. His studies suggest that the non-selected information is actually inhibited (suppressed below baseline levels of attention). Dyer (1973; in Underwood, 1993) has summed the Stroop effect as evidence that a person is unable to avoid processing, albeit un-intentionally, some aspects of any information that they wish to avoid. The Stroop effect has been found to affect various demographic groups differently (Sternberg, 2009). Changes in Stroop test responses have been found as a function of mental age, gender differences that favored females over males. However, measures of interference were not significantly across gender groups. Work on racial prejudice suggests that fast acting automatic prejudice initially interferes with fairness behavior, but may eventually be suppressed across time by a slower, more controlled mechanism. (Braisby & Gellatly, 2012). Neuropsychological Model of the Stroop Effect 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 (Balota & Marsh, 2004). If an identification task involves functions tapping both hemispheres, it is more cognitively complex and thus requires more time to process. This mechanism explains the reaction time data in a Stroop task (Balota & Marsh, 2004). It takes attentional control to reduce interference from the inconsistent words when naming ink colors. Accordingly, individuals with deficits in attentional control (those with dementia of the Alzheimer’s type and schizophrenia) show exaggerated Stroop effects ((Braisby & Gellatly, 2012). These individuals have increased difficulty in suppressing irrelevant information. There is also some evidence of decreased negative priming in individuals with Alzheimer’s disease or schizophrenia (Braisby & Gellatly, 2012; Balota & Marsh, 2004). Bilingual Stroop effect A bilingual Stroop task examined between-language interference among proficient Japanese– English bilingual speakers. For both response languages, a significant between-language Stroop effect was found despite the orthographic dissimilarity between the languages. The magnitude of the between-language interference was larger with the phonologically similar terms (Galotti, 2009). This study was conducted as a replication of part of the original Stroop study with an emphasis on evaluating the effect of interference. Thus, the following hypothesis was proposed: Participants will take more time to complete the interference condition (incongruent color word condition) as compared to the control condition (color / word only condition). Method The study had a single independent variable – the presence of interference, which had two levels – Interference level and control level. One dependent variable was tested, which was the average Response Time of the subjects. Interference was calculated as the difference in response time between the base time for color naming of color blocks and time taken to name the colors in incongruent color-word units. For the control condition, response time was calculated as the difference between the base time and time taken for naming colors of congruent color word units. Since there were two levels on a single independent variable being tested, and the data collected was on an equal interval scale, a t-test was chosen as the appropriate statistical instrument to analyze the data and test the hypothesis. Participants Data was collected from 20 participants who were all exposed to each of the two levels of the independent variable. Of these, ___ were male participants and ___ were female participants. The mean age of the participants was ___. All the participants were students of the _____ Psychology class at the ______ University. Material The study used material that was replicated from the original study by Stroop (1935). Thus, three different stimuli were used to collect data from the participants. First, a sheet with color blocks were used, which was used to measure the base time required by a participant to name colors. An example of the color blocks is given in appendix 1. Next, a sheet of congruent color-word units was used to collect data on the control condition. The congruent color-word units comprised of color names printed in their own color. An example of these appears in appendix 2. Finally, data was collected for the experimental condition using a sheet with incongruent color – word units. In the incongruent units, each color name was printed in a color that was not the same as its name. An example of incongruent color-word units is given in appendix 3. Controls This study used a repeated measures design with a single group of subjects being exposed to each condition. A repeated measures design was used to reduce the amount of possibility of error resulting from interpersonal differences in response time, color recognition and other factors that can affect speed of color naming. All participants were from the same class, which also controlled the extent of familiarity with material similar to the test material. Each color appeared only once in each row and each column, to reduce confusion. Finally, for each of the stimulus sheets, the same color appeared in the same places on all three sheets. Procedure Data was collected from all participants in a classroom setting. The participants were informed about the experiment, and were given instructions. They were asked to raise any doubts they may have, and their queries were answered. Once the participants were comfortable with the procedure to be followed, they were called to the head of the class one at a time, and were presented with the ‘colors only’ stimuli first. This task helped the individual get comfortable with calling out color names, and also provided the data for the base time of the participant. After this, the participant was shown the stimuli for the congruent color-word units, and the time taken to complete this was calculated. Finally, the participant was shown the incongruent color-word units and the time taken to complete this task was also calculated. The participants were asked to call out the color names from top to bottom in each column proceeding from left to right. They were not allowed to follow their progress along the items with their finger, and were not allowed to use any verbal devise to aid color naming. The data collected was tabulated and entered into SPSS. The discrepancy scores for the experimental and the control conditions were calculated for each subject by finding the difference of the experimental stimuli from the base color naming task. The data for the two conditions was than analyzed for significant difference using a t-est. Results This study was conducted to try and replicate the findings of Stroop (1932). Two levels of interference from printed words were tested – presence of interference and absence of interference. Time taken to complete each stimulus was measured in seconds. The mean score of the participants is the colors only task was ____ with S.D. being ___. The mean score for the congruent color-word condition was ____ and S.D. was ___, while that for the incongruent color-word condition was ____ and S.D. was ___. Once the test scores were calculated, the mean score for the Control condition was found to be 12.5 seconds with S.D. = ___ and the mean score for the Interference Condition was 19.5 seconds with S.D. = ___. As the data collected was believed to adequately meet the criteria for parametric testing, and thus, a t-test was computed to test the hypothesis. The computed t-value provided by SPSS was 2.34, which was found to be significant [t (19) = 2.34, p < .05]. Observation of the means showed that the mean score for the interference condition was considerably higher than that of the control condition. Thus, based on these results, it may be said that the present data replicated the finding of the original experiment. Discussion The results of the statistical analyses verified the hypothesis that people take longer to name the colors in the incongruent color word units as compared to the time taken to name the colors in the congruent color-word units. Simply put, the presence of interfering data can hinder the speed of naming ink color. In this case, the interfering task was the word printed; which was a very similar concept (it was also the name of a color) to the target stimulus (the ink color). When the word and the color provide the same information, they do not interfere much with each other, but when they provide conflicting information, they compete for cognitive resources, and can lead to an increase in the time required to process the information, as well as an increase in mistakes in processing. These results are in line with the results obtained by Stroop (1935) and by many others since. Taken along with all the theory collected in the last century, these results may be considered as proof of the costs of experience interference. Although these results are based on laboratory conditions, their implications are relevant to people’s day-to-day lives. There are circumstances people encounter every day that require the need to switch attention back and forth between two or more stimuli. This includes things like, driving a car while talking on a cell phone. The need to focus or divide attention is largely determined by the demands of the user's tasks. There are trade-offs in attention requirements, some automatic in nature; others need deliberate focus to be accomplished. Understanding the detrimental effects that interference has on the ability to process information rapidly (as may be required when driving a car) is important in understanding why interfering events should not be allowed during a task that requires high amounts of attention and skill. References Balota, D. A. & Marsh, E. J. (2004). Cognitive psychology: Key readings. New York: Psychology Press. Braisby, N. & Gellatly, A. (2012). Cognitive psychology. Oxford, U.K: Oxford university press. Galotti, K. M. (2009). Cognitive Psychology. Belmont: Cengage Learning. Sternberg, R. J. & Mio, J.S. (2009). Cognitive Psychology (5th ed.). Belmont: Cengage Learning. Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18 (6), 643–662. doi:10.1037/h0054651 Underwood, G. (1993). The psychology of attention: Volume 1. New York: New York University Press. Appendix 1: Example of the color blocks Appendix 2: Example of the Congruent Color-word units Appendix 3: Example of the Incongruent Color-word units Read More