The Interference of Stroop Effect

Abstract

This experiment investigated that how people’s identification of colors was interfered by incongruent color words and objects. There were 144 participants between the ages of 18 and 50 who are literate in English and not color-blind, each been shown some paper sheets with different color words or objects written on it. They had to name the colors one by one as fast as possible and the time taken for it had been recorded. The results showed that participants took longer time to identify the colors of incongruent color words and objects than just color shapes. It was concluded that people do interfered by incongruent color words or objects to identify the colors thus demonstrating the Stroop Effect.

Do you see what you’ve seen? Seeing things around us including words and variety of colors are the common task we have to do everyday. Most of the words we read on papers are showed in black color. But what if the words are written on different colors, especially those words are color words? Do we perceive the color of the words, or the color word itself primarily? And do we interfered by incongruent color words while identify the color of the words? This study tried to answer these questions whether people are influenced by those different colors and words when naming the colors.

The original Stroop Experiment was conducted by using the nature of stimulus which was the round color shapes versus incongruent color words for participants to name the colors (Stroop, 1935; cited in Cheong, 2004, March). The speed of naming ink colors for every participant was collected to calculate the means and results shown that subjects are slower in naming the incongruent color words. Stroop had concluded that the interference of the incongruent color words slow down the process of naming ink color and therefore with the theory of the Stroop Effect.

The study of Andrade, Henderson & Kamiar in 1996 investigated that the congruency and spelling of the color words do demonstrated by the Stroop Effect in order to measure the response time and accuracy of the participants to identify the color. They were using four lists of words that were divided to two categories that is congruency of words (congruent and incongruent color words) and spelling of words (correctly spelled and misspelled color words i.e. wred instead of red). The speed of naming the color and the accuracy of such action was been observed. The results were showing that only accuracy was affected by the misspelled condition but not response time while congruency had shown interference of controlled process by automatic process.

The original experiment of Stroop Effect had replicated by Hoover, Kuck, Manalo, & Mattingly (1996). They wanted to answer whether Stroop Effect would occur on the emotionality words or color-related words. They had prepared four types of words which were emotional and color-related words (e.g. anger), non-emotional and color-related words (e.g. cherry), emotional and non-color-related words (e.g. nice), and non-emotional and non-color-related words (e.g. desk). Each type of words was shown in two categories as congruent and incongruent color while the non-color-related words’ colors were chosen arbitrarily. The time of answering the task had been taken and the results indicated that color-relatedness words had an effect on response time but emotionality words did not. They concluded that color relatedness of words caused interference as the Stroop Effect but emotionality words did not show significant interference.

MacLeod & Dunbar (1998; cited in Cheong, 2004, March) had replicated the findings of Stroop in the experiment using the same method and they got the same results as Stroop’s. They explained this phenomenon as the Stroop Effect is when the automatic process in reading color words had disrupted the controlled process that naming the ink colors. The two contradictory groups on information had created traffic jam in the information pathway therefore showing the Stroop Effect.

The more recent experiment of Arieh & Algom (2002; cited in Cheong, 2004, March) tried to find out whether the Stroop Effect would occur with a picture-word-naming task. They drew outlines of objects and placed words of the same category as the objects within the outlines’ borders (e.g., an outline of a lemon with the word “banana” written in it). The results showed that the Stroop Effect displayed when naming the pictures i.e. the name of a different fruit inside the borders was interfered the participants for identified the fruit itself.

The present experiment attempts to try out the interference of Stroop Effect while using slightly different materials as past researches. The independent variable is the four test sheets and the dependent variable is time taken to complete each test sheet. Whether the results will replicate here, hypotheses are that the participants will taking longer time to identify the color in test sheet B than test sheet A, shorter time will occur for the participants to complete the task in test sheet A than test sheet D, and the test sheet C will get faster time to get the correct answer than test sheet B. The hypotheses are based on past researches that showing the controlled process will interfered by the automatic process.

Method

Participants

            144 people between the ages of 18 to 50 were participated in this experiment. They were all experimenters’ friends or family members who are English literate and not color-blind in any gender.

Materials

            Four test sheets and a practice sheet are used in this experiment. Test sheet A has been drawn round color shapes as a 50 cents coin’s size; test sheet B is color words with incongruent colors (e.g., red written in blue color); test sheet C consists of color-related words shown in different related colors (e.g., grass written in red color); and test sheet D has shown fruits which in different colors with the usual fruits (e.g. a purple lemon). Each test sheet is included ten objects/words. The practice sheet included two parts of each test sheet (refer to Appendix A for all the four test sheets and the practice sheet). In addition, each experimenter has a stop watch to record the time taken for participant to complete the task.

Procedure

            The experiment was conducted individually in a suitable location with minimum distraction to the participants. They were told that this experiment was investigated about how well people can identify colors and words but the true purpose of the experiment did not been mentioned. The following instruction had been read to each participant:

“I will now show you a page with object/words written on it in different colors. I would like you to name the color in which it is drawn/written as quickly as possible. Please call out the answers aloud to me. If your answer is wrong, I will tell you and you will need to repeat it” (cited in Cheong, 2004, March).

            The practice sheet was shown to the participant to check whether they fully understood the instruction. The explanation was repeating until they had understood. Then the four test sheets were shown one in a time for them to say the answers out loudly so that experimenter could check the answers correctly. If they were wrong, experimenter would say “wrong” and let them give the answers corrected. The exact time taken for them to complete the task of each test sheet had been recorded using a stop watch and the means of the time taken from all the participants had been calculated.

Results

            The time taken from all the participants was totaled and the means had been calculated. A lower mean shown that the time taken was shorter whereas a higher mean shown the time taken was longer (in second). Different means were obtained for each test sheet as recorded in Table 1.

Table 1

Mean time taken to identify colors in the test sheets

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Test Sheet A               Test Sheet B               Test Sheet C               Test Sheet D

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     9.54                             14.55                         10.58                          10.18

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            The results shown in Table 1 indicated the participants took the longest time to complete the task in test sheet B (incongruent color words) which is 14.55 whereas the shortest time taken is 9.54 to complete test sheet A (round color shapes). However, test sheet C & D get similar results which are 10.58 & 10.18 indicating the different objects/words on these test sheets did not make much different for participants to name the colors.

Discussion

            The results showed that incongruent color words had the most effect of interference for the participants while round color shapes without words’ appearance did not show interference. Thus supported the hypotheses of  the participants was answering test sheet B slower than test sheet A, test sheet A faster that test sheet D and test sheet C faster than test sheet B.

            The interference of Stroop Effect was perfectly showed in this experiment’s results and consistent with the experiment of Stroop (1935). This study had successful replicated the findings of MacLeod & Dunbar (1988) that the automatic process disrupted the controlled process.

            Even the results obtained were satisfied by the experimenters, several weaknesses had been discovered in this experiment. For instance, the time taken did not recorded accurately by the experimenter. The immediate action of pressing the stop watch may be slightly faster or slower. Second, the participants’ emotion such as nervousness or physical health might influence their performance in the experiment. In addition, the environment of proceeded the experiment may not be suitable. Another weakness showed that the test sheets may not being prepared carefully such as the size of words/objects may be too big or too small for the participants to read comfortably. Lastly, the participants’ consciousness strongly influenced the accuracy of this experiment such as they are night people but the experiment took place in the morning.

            In conclusion, this study showed the evidence of the phenomenon of Stroop Effect strongly. While further research needs to be more specific and more accuracy in order to increase our knowledge of cognitive process.

References

Andrade, J. , Henderson, L. &  Kamiar, A. (1996). Automaticity in Relation to the Stroop Interference Effect as a Consequence of Misspelled Color Words. Retrieved April 3, 2004 from the World Wide Web: http://www.psych.ufl.edu/~levy/96_5.htm.

Arieh, Y. & Algom, D. (2002). Processing Picture-Word Stimuli: The contingent nature of picture & of word superiority. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28 (1), 221-232. In Cheong, W. (2004, March). The Stroop Effect Tutorial. Lecture presented to PY101 (March), HELP Institute.

Hoover, H. L. , Kuck, D. E. , Manalo, J. Q. , & Mattingly, M. C. (1996) Color Relatedness and Emotionality: Further Analysis of the Stroop Effect. Retrieve April 4, 2004 from the World Wide Web: http://www.psych.ufl.edu/~levy/96_2.htm

Macleod, C.M. & Dunbar, K. (1988). Training and Stroop-like interference: Evidence for a continuum of automaticity. Journal of Experimental Psychology: Learning, Memory, and Cognition, 14, 126-135. . In Cheong, W. (2004, March). The Stroop Effect Tutorial. Lecture presented to PY101 (March), HELP Institute.

Stroop, J.R. (1935). Studies in interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643-662. . In Cheong, W. (2004, March). The Stroop Effect Tutorial. Lecture presented to PY101 (March), HELP Institute.