Psychological report on the Stroop effect

By Thomas Silk
Abstract
The aim of this experiment is to study autonomic processes by replicating the previously carried out Stroop effect by using numbers.
My hypothesis was that participants will be slower to properly identify the colour of ink when the ink used to produce colour names different from the ink. That is, observers were slower to identify red ink when it spelled the word blue.
A number of 20 random participants aged in between 17-18 were recruited to participate in this experiment. Participants were presented with one condition for 10 participants and a second for the other 10.The first condition had the words of colours and were printed in a different colour ink, and the second condition the words were printed in the corresponding colour. Based on the results, participants took a considerably longer time to say the number of number in the incongruent condition than in the congruent condition. This corresponds to the earlier research carried out by Stroop. Therefore, it can be said that the powerfully autonomic nature of reading words is as same as reading numbers, as it is such a well-learned automatic activity it does interfere with the task.
Introduction
When you first learned to tie shoelaces you needed to carefully think through each step of the process. Now, you probably do not even seem to think about the steps, but simply initiate a series of movements that seem to proceed without any further influence. When a behaviour or skill seems to no longer require direct interaction, cognitive psychologists say it is automatized.
Many behaviours can become automatized: typing, reading, writing, bicycling, piano playing, driving, etc. Automatization is interesting because it is an important part of daily life. We perform a variety of automatized behaviours quickly and effortlessly. In some cases people report that they do not consciously know how the behaviour is performed, they just will it to happen, and it does happen. To explore properties of automatized behaviours cognitive psychologists often put observers in a situation where an automatized response is in conflict with the desired behaviour. This allows researchers to test the behind-the-scenes properties of automatized behaviours by noting their influence on more easily measured behaviours. This demonstration explores a well-known example of this type of influence, the Stroop effect.
The Stroop Effect was first reported by John Ridley Stroop in 1935, and looks at how our brains process words. We process these letters so quickly that we struggle to be able to say the colour rather than the word
Stroop (1935) noted that observers were slower to properly identify the colour of ink when the ink was used to produce colour names different from the ink. That is, observers were slower to identify red ink when it spelled the word blue. This is an interesting finding because observers are told to not pay any attention to the word names and simply report the colour of the ink. However, this seems to be a nearly impossible task, as the name of the word seems to interfere with the observer's ability to report the colour of the ink. A common explanation for the Stroop effect is that observers (especially college undergraduates) have automatized the process of reading. Thus, the colour names of the words are always processed very quickly, regardless of the colour of the ink. On the other hand, identifying colours is not a task that observers have to report on very often, and because it is not automatized it is slower. The fast and automatic processing of the colour name of the word interferes with the reporting of the ink colour. The Stroop task, and its many variations, are a commonly used tool in cognitive psychology to explore how different types of behaviours interact. This demonstration allows you to participate in a simple version of the Stroop task. The actual words have a strong influence over your ability to say the colour of the words. The interference between the different information (what the words say and the colour of the words) your brain receives causes a problem.
Stroop's research originated from James McKeen Cattell (1886), who found that responding to objects and colours took longer to read aloud than words. The association between the name and idea took place so frequently that it became an automated process. Unlike with pictures and colours, an intentional effort had to be made. The Stroop effect was used to discredit the theory of controlled and automatic processing by Schneider and Shiffrin (1977). Their theory concluded that controlled processing was slower than automatic. Also, once a task was automated it could be done with no conscious effort, and this would affect all other activities. Sheibe, Shaver and Carrier (1967) found that if the word was congruent, it would be identified quicker than if it was incongruent. This also supports for Stroop's investigation (1935). However, all prior researchers were interested in studying the interference between conflicting processes and none thought to combine colours and words until Stroop. Since Stroops original experiment, there have been many variations made to test different phenomena. For example, sorting and matching versions of the colour word task, the picture-word interference task, and the stroop colour-word test. The aim of this experiment is to prove Stroops theory, and to investigate how interference affects participants' ability in both
There are several theories used to explain the Stroop effect and are commonly known as ‘race models’. This is based on the underlying notion that both relevant and irrelevant information are processed in parallel, but “race” to enter the single central processor during response selection.
One theory is the processing speed theory. This theory suggests there is a lag in the brain's ability to recognize the colour of the word since the brain reads words faster than it recognizes colours. This is based on the idea that word processing is significantly faster than colour processing. In a condition where there is an regarding words and colours (e.g. Stroop test), if the task is to report the colour, the word information arrives at the decision-making stage before the colour information which presents processing confusion. Conversely, if the task is to report the word, because colour information lags after word information, a decision can be made ahead of the conflicting information.
A second could be selective attention. The Selective Attention Theory suggests that colour recognition as opposed to reading a word, requires more attention, the brain needs to use more attention to recognize a colour than to word encoding, so it takes a little longer. The responses lend much to the interference noted in the Stroop task. This may be a result of either an allocation of attention to the responses or to a greater inhibition of distractors that are not appropriate responses.
A third possibly the automaticity theory. This theory is the most common theory of the Stroop effect. It suggests that since recognizing colours is not an “automatic process” there is hesitancy to respond; whereas, the brain automatically understands the meaning of words as a result of habitual reading. This idea is based on the premise that automatic reading does not need controlled attention, but still uses enough attentional resources to reduce the amount of attention accessible for colour information processing. Stirling (1979) introduced the concept of response automaticity. He demonstrated that changing the responses from coloured words to letters that were not part of the coloured words increased reaction time while reducing Stroop interference.
Or finally parallel distributed processing. This theory suggests that as the brain analyses information, different and specific pathways are developed for different tasks. Some pathways, such as reading, are stronger than others, therefore, it is the strength of the pathway and not the speed of the pathway that is important. In addition, automaticity is a function of the strength of each pathway, hence, when two pathways are activated simultaneously in the Stroop effect, interference occurs between the stronger (word reading) path and the weaker (colour naming) path, more specifically when the pathway that leads to the response is the weaker pathway.
Method
Design
The research method I used was a laboratory experiment. The reason I chose this method was because it can be replicated very easily. All the instructions, debrief and brief are standardised. And all materials are quickly printed off if needed. Also because it makes it easier to control the experiment and the variable involved.
Participants
In total 20 participants were used: 10 males and 10 females, all gained through opportunity sampling, they were all year 12 A level students so aged 17-18 years old. It was made sure that no one in our psychology class was used as a participant to keep good reliability. I generalised my data to the target population of A level students.
When selecting the students I simply would walk around our 6th form area and stop and ask random students if they would like to take part in the investigation.
Materials
There were two conditions in this investigation, the first condition the colour of the word corresponded directly to the word, and the second condition the colour of the word was completely different to the word. The words used were in large block capital writing and were printed from word. There were 10 different words and colours for each condition. The participants all read standardised instructions beforehand. A stopwatch was used to keep the time it took for participants to correctly identify the words. At the end of the investigation a debrief was read to all participants.
Procedure
Sampling Method; I used opportunity sampling in this experiment, meaning I chose the first few 6th Form students I saw around school. This method of sampling was mainly used because it does not require a great amount of time, and it is relatively non-strenuous. Ethical Issues; In this experiment there were certain things we had to do and offer, as they are thought of as ethical issues. The first thing is offering a briefing, at the start, and a debriefing once the experiment was over. Sometimes this is done verbally, but in our case, as it was a reading task, we decided to have them typed on the page. In the briefing we took a friendly approach, and clearly stated that 'you can withdraw at any time if you feel, for any reason, you do not want to continue.' Although we did not explain every detail, we got our point across. In the debriefing we explained that 'All results will remain confidential, and your name will not be mentioned. We also offered the participants the chance to withdraw their information if they wanted.

Results
(A table showing the time taken to show time taken to correctly identify the colours in the congruent and incongruent condition.) Participant number | Conflicting colour (s) | Rank order | Participant number | Non conflicting colour(s) | Rank order | 17 | 22.03 | 19 | 7 | 13.07 | 5 | 15 | 22.05 | 20 | 14 | 13.02 | 4 | 3 | 18.25 | 12 | 20 | 18.95 | 14 | 13 | 19.0 | 15 | 5 | 19.7 | 17 | 11 | 18.83 | 13 | 8 | 11.6 | 2 | 2 | 14.94 | 8 | 19 | 9.3 | 1 | 4 | 14.0 | 6 | 1 | 19.8 | 18 | 6 | 19.06 | 16 | 10 | 12.9 | 3 | 9 | 16.08 | 10 | 16 | 17.8 | 11 | 12 | 16.05 | 9 | 18 | 14.5 | 7 |

Measures of central tendency | Conflicting colours(s) | Non—conflicting colours(s) | Total number of scores | 10 | 10 | Mean score | 18.02 | 15.06 | Mode | 14 | 9.3 |

Measures of dispersion | Conflicting colours | Non—conflicting colours | Standard deviation | 2.76 | 3.73 | Range | 8.05 | 10.50 |

In summary, Condition A (the conflicting group) on average took 18.02 seconds to correctly identify all of the colours on the cards, whilst condition B (Non conflicting group) on average took 15.06 seconds to correctly identify all the colours on the cards shown to them (see appendix). The standard deviations of both sets of data show that Condition B was more widely dispersed than in condition A, with results of 2.76 and 3.73. This can also be seen in the range values which are 8.05 for condition A and 10.50 for condition B. The results generally show that non conflicting group performed better than the conflicting group. The mode value for condition A was 14, and 9.3 for condition B. In general the non-conflicting group took the less time to identify the words correctly, as predicted in the hypothesis.

Discussion
Explanation of findings
The statiscal analysis shows that words that are written In the congruent ink to the word itself are recognised faster than incongruent ink. This means that the experimental hypothesis of ‘participants will be slower to properly identify the colour of ink when the ink used to produce colour names different from the ink. ‘ can be retained and the null is rejected. When N=10 and N2 =10 . the critical value of U at the P≤ 0.05, the level of significance for a one tailed test is 21. The observed value of U must be equal to or less than the critical value to be significant. In our case the value of U was less than the critical value, allowing us to reject the null hypothesis and retain the experimental.
The data showed us that there was some insignificant differences in the participants individual abilities to correctly identify the ink and names, but overall congruent colours were easier to correctly observe than incongruent ones. This can be seen in the results of participant 4, as their time taken was as low as some of the results in the in the non-conflicting group. But as the measures of tendency and dispersion show this hardly affected the end results.
The dispersion of the data was quite interesting it showed that there was a larger spread of the data from the non-conflicting colours group, than there as for the conflicting group. This may be explained by the fact that even though all of our brains are similar in fact nearly identical, the interworking’s of them all are different in each person, so even though we all recognise non conflicting colours faster, there is a lot of difference in the speed of this from person to person. However with the conflicting colours the general spread of data is less, showing that we all have very extremely similar ways of processing information and the result of this processing method is similar lag time to identify the colours.
Relationship to background research
Stroop (1929) found that there is interference in the reaction time of a task. When the name of a colour (e.g., "blue", "green", or "red") is printed in a colour not denoted by the name (e.g., the word "red" printed in blue ink instead of red ink), naming the colour of the word takes longer and is more prone to errors than when the colour of the ink matches the name of the colour. These findings correspond with the ones from this study. The methodology behind bother experiments, Stoops and this one were very similar. This experiment also used the same colours and colour variations in the ink that stroop used in his original experiment, this could have made the study unreliable as we do not know whether certain colours are more easily recognised than others. It is hard to know all variables beforehand, some often don’t develop until the experiment. Also some colours could have a more personal meaning with a participant, or just maybe its their favourite colour. This could be explained by the leves of processing model (Baddely and Hitch 1974), who suggest that deeper processing leads to better memory. They said that Semantic processing was the deepest, and therefore resulted in better recall. This could be changed from recall to identifying colours in a Stroop test. The findings of this study closely match up to the data collected from similar studies, proving stroops theory correct.
Limitations and modifications
The main problem encountered was the sample bias. The participants that were used were all psychology students from university, and cannot be generalised to society. Therefore the results gained are unreliable. The experiment can also be heavily criticised for being gender bias, as there were only five males in comparison to sixteen female participants. This also had a confounding affect on the results as shown in fig 1 and 2, as male participants had a faster reaction time than females. Therefore we cannot generalise our findings as the sample used was not equal. Another limitation was the effect the uncontrolled variables had upon the investigation such as noise and light which acted as interference and could have affected the reaction time and number of errors. Improvements are required to increase the validity of the results. A larger sample size would make this experiment more reliable and more able to generalise the findings. To improve this aspect further, a wider age range would increase the validity as age could have an affect on attention. This could be used to research further into the mind of individuals. Furthermore, a more diverse gender would be beneficial in increasing the validity of the experiment as there are key differences between male and females as has been indicated throughout the field of psychology. In order to develop this investigation, interference can also be measured aswell as reaction time. This would produce results of a higher accuracy, increasing the validity. However, this would require the external environment to be adapted accordingly, thus eliminating any extraneous variables that could alter the results.

References
Charles Stangor (3rd Ed) Research Methods for the Behavioural Sciences
Elizabeth A. Syles (1997). The psychology of attention
Jensen, A. R., & Rohwer, W. D., Jr. (1966). The Stroop colour-word test: A review. Acta Psychologica.
MacLeod, C.M. (1991) Half a century of research on the stroop effect: an intergrative review. Psychological Bulletin, 109, 163-203
MacLeod, C.M. (1991). John Ridley Stroop: creator of a landmark cognitive task. Canadian Journal of Psychology.
MacLeod, C. M., & MacDonald, P. A. (2000). Interdimensional interference in the Stroop effect: uncovering the cognitive and neural anatomy of attention. Trends in Cognitive Sciences.
MacLeod, C. M., & MacDonald, P. A. (2000). Interdimensional interference in the Stroop effect: uncovering the cognitive and neural anatomy of attention. Trends in Cognitive Sciences. http://www.rit.edu/cla/gssp400/sbackground.html https://en.wikipedia.org/wiki/Stroop_effect

Conflicting colours

Non-conflicting colours

Standardised instructions
Hello participants
You are here today to partake in a recall experiment. Everybody’s results will remain confidential, and any specific references to you or your data will be made in terms of the participant number you have been enlisted with. Anybody who does not wish to take part may leave now. You can also leave at any point during the experiment and can withdraw your data afterwards.
When I have finished speaking you will see a series of words on the screen. As each words is put on the screen in front of you, you must say the colour that the word is written in, you will be timed how long it takes for you to correctly identify all the words colours. You will then be debriefed afterwards.