Exploring the Stroop Effect by using numbers

Abstract

The purpose of this experiment is to study automatic processes by replicating the previously carried out Stroop effect by using numbers. This experiment was conducted by recruiting 8 participants (4 males and 4 females), who are working in a head-office of Save the Children Organization in Yangon, selected by an opportunistic sample. Participants were presented with a Stroop-experiment-task sheet which consists of two parts which was the congruent and incongruent conditions.

Time was taken and recorded for each participant to count the number of digits in the congruent and incongruent conditions. The results found that the participants took a significantly longer time to count the number of digits in the incongruent condition than in the congruent condition. This matches with the former research carried out by Stroop. Therefore, it can be concluded that the powerfully automatic nature of reading words is as same as reading numbers, as it is such a well-learned automatic activity it does interfere with other tasks. (Word count = 160)

Introduction

Attention is a system, which allows people to choose and process certain significant incoming information. According to Treisman (1964), selective attention means the ability to concentrate on one task at a time whilst rejecting any external stimuli, which may be diverting. But divided attention means the ability to separate ones attention between two or more tasks. If one of these tasks becomes an automatic process it becomes easier to separate ones attention between these two tasks. However, sometimes rather than being beneficial, interference can happen between the controlled process and the automatic process.

Psychologists have often found that the strongly autonomic nature of reading words, as it is such a well-learned automatic activity can interfere with other tasks. This idea has been researched by a number of researchers. Healey (1976) conducted a research into how people automatically process frequently occurring words such as “of” in sentences and so find it harder to focus on module letters. She presented participants with a piece of English prose and asked them to read it and circle all the t’s in the paragraph. Participants frequently missed out the t’s in common words such as “the” and more easily identified the t’s in more uncommon words.

This shows that people acknowledge high frequency words such as “the” as whole units rather than by their individual letters, so automatically process them. This powerfully autonomic nature of reading words is also obvious in the following research carried out by “Stroop”. Stroop (1935) carried out a study into autonomic processing, by devising the Stroop effect. In this, he asked participants to read a list of colour words written in black ink. This, obviously a very simple task was uncomplicated and easy for the participants to achieve. Following this, participants were requested to read a list of colour words written in incompatible colored inks, (e.g., the word “red” written in blue colour ink) and to call out the colour ink the words were written in.

Although this task seems very simple at first and is only matter of simple colour identification, Stroop found that it took the participants considerably longer to accomplish this task than the previous. The reason is that the powerful autonomic (unconscious) nature of reading words meant that participants automatically wanted to read the words rather than the colour ink they were written in. Thus, even though the participants didn’t often read the colour word out loud, there was a time delay even as the participants thought of the correct response (the color ink). In this piece of research, there is the aim to carry out a modification on the experiment on automatic processes carried out by Stroop and to find out whether the results keep up a correspondence.

The experimental hypothesis is that the length of time taken for participants to count the number of digits in incongruent condition will be greater than the length of time taken to count the number of digits in congruent condition. The null hypothesis is that there will be no difference in the length of time taken for participants to count the number of digits on incongruent list and the length of time taken to count the number of digits on congruent list. (Word count= 534)

Method

(a) Research design: The repeated-measures design was used for this experiment, so all subjects experienced each of the experimental conditions. In other words, the experiment was a within-subject design. The independent variable was the incongruent and congruent stimuli and the dependent variable was the time taken to count the number of the digits. The incongruent condition was the “Stroop” condition, and the congruent condition was controlled condition. No change was made to the independent variable, meaning the design is parallel between the values of the dependent variables attained from incongruent and congruent conditions for each participant. Confidentiality of participants had to be ensured, by anonymity.

(b) Subjects: The subjects were 4 males and 4 females between the ages of 30 and 36. All participants were staffs who are working in a head-office of Save the Children organization in Yangon, and they all are graduated. They are selected by using the convenience sampling method. (c) Materials: Two lists of numbers were used as stimulus materials. In List 1, there were 32 congruent stimuli – the number name and the number of digits are the same (e.g., “1”, “22”, or “333”), and in List 2, there were 32 incongruent stimuli – the number name and the number of digits are different (e.g., “3333”, “111”, or “2”).

The other materials used in this experiment were a stopwatch accurate to the nearest second to measure how long it took each participant to complete the task, a summary data sheet and a pen to record results, and an actual instruction gave to the subjects (see in appendices A). (d) Procedure: Before the experiment began, the participants were informed they would be taking part in a piece of psychological research, they have the right to leave at any time, and their details would be secret. Then, presumptive consents from the participants to carry out and use the results of the experiment were obtained.

Each participant was taken into a same, quite room, which excluded the others from seeing what might be going on. As one participant entered the room, the participant was greeted by the researcher and asked to read an instruction sheet. Then the participant was presented with a list of numbers and was then instructed to “count the number of digits aloud in each row as quickly as possible, to read from the top to the bottom, not to skip any items, and if there be any mistakes, not to stop, continue with the task”.

When the participant was ready, he/she was allowed to read one list from which the stopwatch was simultaneously started and at the end, it was stopped and time taken was recorded. A two-minute interval was assigned between lists. After this interval was over, the same procedure was conducted with the second list. On completion of the second list and time recorded, the participant was debriefed. They were then thanked for taking part and allowed to leave.

(e) Control: Since the experiment design was repeated-measures, there may be order effect as confounding variable. That is, the participants may learn how to do it due to the repetitive nature of the experiment. This problem is counterbalanced with half of the subjects starting with the List 1(congruent condition) and half starting with the List 2 (incongruent condition). For 2 males and 2 females, List 1-List 2 order was used and for the other half, List 2-List 1 order was employed. (Word count = 566)

Results

Based on the data obtained, the mean score and standard deviation for each condition was calculated and then the following summary table was created. The more detailed evidence such as raw scores and calculation can be found in Appendices B. Summary table 1:

| List 1 (Congruent condition)| List 2 (Incongruent condition)| Mean (second)| 17.50| 28.62|
Standard deviation| 2.78| 3.85|

From the table the accurate value for the congruent mean is 17.50 whereas the value for the incongruent mean is 28.62. It is evident that the incongruent mean is considerably higher than the congruent mean, which shows that it took considerably longer for participants to count the number of digits on incongruent list than to count the number of digits on congruent list. In order to measure the spread of data around the mean, the standard deviation of the time taken to read the congruent and incongruent lists of numbers was calculated. The standard deviation for the congruent list and the incongruent list were 2.78 and 3.85 respectively.

To test experimental hypothesis, t test for repeated-measures design was used. From a t distribution table, a level of significance was set at alpha = 0.05 confidence level for the one-tailed test. For α = 0.05 at the t distribution for df = 7, the critical region consisted of the extreme 5% of the distribution and has boundaries of ±1.895. Since the computed value of t (+5.1) falls in the critical region, the null hypothesis can be rejected in favor of the alternative hypothesis. This basically means that the alternate hypothesis, that the length of time taken for participants to count the number of digits in incongruent condition will be greater than in the congruent condition, can be confirmed. (Word count = 286)

Discussion

The aim of this research was to replicate the original experiment carried out by Stroop and gain the similar results. The aim was achieved, as the results obtained supported the experimental hypothesis that it would take considerably longer for participants to count the number of digits in the incongruent condition than in the congruent condition. It is indicated by comparing means and standard deviations in both conditions, and is further supported by the results of t test. Because the t value obtained falls in the critical region, the null hypothesis, there will be no difference, was rejected at the 0.05 confidence level. This conclusion supports findings from previous research done by Stroop and other researchers into the interference effects between automatic and controlled processes.

In this experiment, the experimental room used was relatively private and excluded variables which might have influenced the results such as noise etc. These might have taken concentration off of the task at hand but this problem was eradicated. Moreover, it is found that the participants who read List 2 first taking a little longer than those who had read List 1 first (see in summary table (2.1) of Appendices B). This has showed that the design of the experiment was effective, taking a balance of both into consideration. However, the experiment was small scale and the data used was limited.

Because the sample includes only staffs from Save the Children organization of a particular age range, the results are not generalizable to the whole population. The experiment itself was very artificial and carried out in a non-natural environment. People would not usually find themselves in situations where they have to read out lists of words or numbers from a sheet of paper in real life. The experiment therefore lacks ecological validity and the findings cannot be applied to real life situations. When running the experiment, some problems were encountered. Although the private experimental room was effective in excluding other variables which might have influenced the results such as noise, it made the participants more anxious.

The researcher needs to use relaxation techniques to reduce their anxiety before reading the lists. At the time of the test, there was only one researcher present in the room, it was difficult to record the exact time taken for each participant to complete the task. If there were two independent researchers, they can agree on what they see and what they record, and then the conclusion of this study will be more reliable. Although there was some weakness in experimental manipulation, the results gathered produce wider support to the suggestion that automatic processes have an effect on controlled processes.

Other research may also be carried out in areas of automatic and controlled processes for example investigating the emotional state of participants in controlled conditions. Moreover, future studies into the Stroop effect could include using shapes and objects rather than just numbers or colors to see whether the autonomic nature of reading numbers or words is just as strong when paired with using objects or other shapes. (Word count = 508)

Conclusion

The research was carried out in an effort to prove that the experimental hypothesis, “the length of time taken for participants to count the number of digits in incongruent condition will be greater than in congruent condition”, was true. The null hypothesis, that there would be no difference in the length of time taken for participants to count the number of digits on the incongruent list and on the congruent list, was disproved.

It can be said that the strongly automatic nature of reading words is as same as reading numbers, as it is such a well-learned automatic activity it does interfere with other tasks. Therefore the results the researchers in this case acquired were agreeing with those formerly done in this field of research. (Word count = 125) Total word count = 2178.

References
Rice, D. and Haralambos, M. (2013.) An experiment into the Stroop effect. Retrieved from http://www.123helpme.com/an-experiment-into-the-stroop-effect-view.asp?id=150197 Healey (1976). Automatic and strategic processing. Retrieved from http://www.books.google.com/books?isbn=0805824162

Fan, R. M. (2001). Principles of Social Research, unit-9, 11 and 12. Hong Kong, China: The Open University of Hong Kong. Stroop, J. R. (1935). Classics in history of psychology: Studies of interference in serial verbal reactions. Retrieved from http://ebookbrowse.com/classics-in-the-history-of-psychology-stroop-1935-pdf-
d142657251. Treisman, A. M. (1964). Selective attention in man. Retrieved from http://psycnet.apa.org/index.cfm?fa=buy.optionToBuy&id=1969-07664-001. Appendices