However, there are costs associated with automatic processing as it may interfere with the information people are trying to attend to, making an easy task difficult to perform. A classic phenomenon that demonstrates this is the Stroop effect, which shows the difficulty in naming ink colours of words that are themselves name of colours (Goldfarb & Henik, 2007). Since Stroop’s publication in 1935 over 400 studies were published investigating different aspects of this phenomenon (MacLeod, 1991).
The rationale for this experiment is to retest one of the variations of the Stroop effect manipulating the stimuli the participants were confronted with (colour-related versus colour-neutral words) and to quantify the intrusion of automatic processing. The research hypothesis was that the time taken to identify the ink colours of a list of colour-related words will be longer than that of a list of colour-unrelated words. This is a one-tailed hypothesis. The null hypothesis was that there will be no difference in the processing time for the two lists.
Methods
Design
A within-participants design was employed. The independent variable was represented by two conditions; two word lists printed in various coloured inks. One list consisted of colour-related and the other of colour-neutral words. The dependent variable was the time needed to name the ink colours. This was measured to the nearest whole second.
Participants went though both conditions the same day, one right after the other. The order of the conditions was counterbalanced. Half of the participants did Condition 1 first and then Condition 2, inversing the order with the other half. Each word was used the same number of times in both conditions (five times each). The exact amount of words and colour of ink were presented in both conditions (30 words) and all words matched for length. Also the order in which the different colour inks were used was the same in the experimental and the control condition. The researchers remained as objective as possible during the whole experiment and the instructions were given in a standard way (Appendix 1), without favouring a certain outcome.
Participants
The twenty-two participants that took part in this experiment were recruited from amongst colleagues at the Open University, or their friends and family members. The panel consisted of 12 females and 10 males between the ages of 18 and 69. All were fluent English speakers and had normal or corrected-to-normal eyesight. None suffered from any colour interpretation difficulties.
They were first told that they would be taking part in a psychological experiment about cognitive psychology and all signed a consent form (Appendix 2). They were fully debriefed afterwards and informed about the real aim of the study. All were naive to the hypothesis of this experiment and without previous knowledge of cognitive psychology. None received any incentive for participating. All responses were taken for further analysis without need to exclude any of the results.
Materials
Two lists of 30 words located on two columns were prepared on separate A4 sheets. The list in the experimental condition (condition 1) contained colour-related words printed in an incongruent colour, while in the control condition (condition 2) all words were colour-neutral (Appendix 3). Each word appeared five times in its list, the order being randomised. Each word was printed in one of six colours (red, yellow, green, orange, purple and blue). The colours were randomly distributed between the words, but the same colour sequence was present in both lists. All words were in capital letters printed in 36pt Arial Bold on white matt paper.
The exact same instructions were used in both conditions and the response times were written down on a response sheet (Appendix 4). The time taken to complete each condition was measured to the nearest second using a stopwatch.
Procedure
Participants were asked to participate in a cognitive psychology experiment that would take around 5 minutes to complete. Everybody who consented signed a consent form. Participants were tested individually in a quiet, well illuminated room and informed that they may withdraw at any time they wish. The age and gender of the participants were recorded. The same instructions were read verbatim to each participant and all were asked if they fully understood these and shown the exact same two examples (Appendix 1).
The sheet named “Condition 1” was placed face down in front of the first participant. After turning over the page, the participant was asked to start identifying the colours and timing began. Once finished, the time to perform the task was recorded by the nearest second. Subsequently, the sheet named “Condition 2” was placed face down in front of the participant and all steps were followed in the same manner as before. The order of presentation of the lists was randomised. For the next participant, Condition 2 was first done and then condition 1. The order of the conditions was continuously swapped after each participant.
To conclude, debriefing took place. Participants were asked if they had any questions and briefly introduced to the automatic and controlled attentional processes, the Stroop effect and how this can be investigated with help of the data collected in this experiment.
Results
The research hypothesis in this experiment was that that the time taken to identify the ink colours of a list of colour-related words will be longer than that of a control list of colour-unrelated words. The time taken to identify the colour of the words on each list was measured to the nearest second.
Table I shows that the mean in condition 1 was 25.18 seconds (standard deviation 6.45) and the mean in condition 2 was 21.64 seconds (standard deviation 5.18). Participants needed more time to perform the task in condition 1 than in condition 2, with the mean time taken in Condition 1 being 3.54 seconds longer than in condition 2. A paired-samples t-test was conducted on these data, which revealed that there was a statistically significant difference between the time taken to identify the ink colour of the list of colour-related words and that of the list of colour-neutral words, with response time being higher when the words were colour-related (t (21) = 4.625, p< 0.0005, one-tailed, d = 0.61). The effect size shows a difference between the conditions of 0.61 standard deviation points. This can be considered a medium/large effect of the IV on the DV. Based on this result the null hypothesis was rejected.
Discussion
The results showed a statistically significant increase in the time taken to identify the colour of colour-related words over the neutral words, suggesting an interference of automatic processing during the colour identification task. The significant time difference between both conditions supports the research hypothesis of this study and the conclusions drawn by previous researchers, which states that automatic processing cause conflict in situations of incongruence between words and colours (MacLeod, 1999). The experimental outcome is also consistent with the limited-capacity theory of Kahneman's model and the definitions of automaticity cited by Shiffrin and Schneider. The results suggest that, despite attempting to focus on the colour of the ink, the automatic process of linking the colour-related words to certain colours was activated and conflicted with the participant’s attention to the ink. If controlled and automatic processes would not be in conflict for attentional resources, then it would be reasonable to expect the type of word (colour-related or colour-neutral) having no significant effect on the reaction time. However, the fact that the present study showed a significant effect on the reaction time suggests that automatic and controlled processes coexist and are sometimes in conflict with each other.
The reason for an increase in the time taken in condition 1 is unclear. Some of the participants seemed consciously to slow down when identifying the ink colour of coloured-related words, possibly to be more attentive. Others would read both lists at the same speed but, if mistakes were noticed, would take time correcting them. Possibly some period of practice would have allowed the participants to habituate to the task, reducing the differences in average time taken in both conditions.
It would be interesting to retest the robustness of the Stroop effect replacing the colour-related words with non-words that sounds like colours (e.g. bloo or wred) to measure selective attention and processing speed, assessing the amount of the interference and quantifying the effect of the phonological similarity between non-words and colours.
While the execution of the experiment was simple, there were some difficulties based on the fact that it has been conducted in two phases by different researchers who did not collaborate to operationalise it. This might have arisen possible confounding variables as it was not clear in what type of environment the first 16 participants were tested and at what time of the day the testing took place. The last six participants were all tested in the early morning in a quiet environment. If it was the case in the first sixteen cases, is unclear.
In conclusion, the idea of automatic versus controlled processing is clearly evident through previous results and the present research. However, future research in this area should attempt to avoid to a maximum confounding variables such as the time of the day in which participants are tested and the kind of environment where the test occurs, as this could affect the results.
References
Edgar, G. (2007) Perception and attention. In D. Miell, A. Phoenix, & K. Thomas (Eds.), Mapping Psychology (2nd ed., pp.3–50). Milton Keynes: The Open University.
Goldfarb, L., & Henik, A. (2007). Evidence for task conflict in the Stroop effect: Human Perception and Performance, 33(5), 1170-1176.
MacLeod, C.M. (1991). Half a century of research on the Stroop effect: An integrative review. Psychological Bulletin, 109(2), 163-203.
Appendices
Appendix 1: Instructions & examples
Appendix 2: Consent form
Appendix 3: Stimuli: Condition 1 & Condition 2
Appendix 4: Response sheet
Appendix 5: Raw data
Appendix 6: SPSS print-out of t-test
Appendix 1: Instructions & examples
The following instructions were read verbatim to each participant.
In a moment I will place a sheet of A4 paper in front of you that contains two columns of words. You will notice that the words are written in six different colours of ink – red, blue, green, yellow, orange and purple. What I would like you to do is to say out loud the colour of the ink each word is written in. Start with the word at the top of the left column and work downwards. When you have finished all the words in the left column, start on the right column. Remember, I do not want you to read the word itself out to me, instead I want you to state what colour of ink it has been written in. You should work through the list as quickly as you can.
To help you, here are two examples:
CHAIR
For the item above you would respond ‘blue’.
HOUSE
For the item above you would respond ‘red’.
Do you understand what you will be required to do?
(If yes, then proceed to task. If no, go through the examples again.)
Appendix 2: Consent form
Consent to participate
I have been asked to participate in an experiment that investigates one aspect of cognitive psychology and give my free consent by signing this form.
- I have been informed about the research and why it is taking place.
- I understand that my participation in this research is voluntary.
- I understand that I can withdraw from the research at any time.
- I understand that my data will be anonymous.
- I understand that I will be provided with a debrief after taking part in the experiment.
Signature _______________________________
Date ___________________________________
Appendix 3: Stimuli: Condition I & Condition II
Condition 1
Condition 2
Appendix 4: Response sheet
Appendix 5: Raw data
Data from twenty-two participants with age, se
Appendix 6: SPSS print-out of t-test
