Selective attention and the stroop effect

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Selective attention and its theories have been modified over many years, early ones such as 'bottleneck' theories have led to more recent theories that information can be processed through a series of automatic processes or unconsciously. It is suggested that many everyday tasks such as reading are tasks that can be overlearned and become automatic, these automatic tasks can be difficult to control. This report examines a study of the Stroop effect which looks at whether automatic processes could interfere with colour identification task. The findings of this report show that automatic processes did interfere with colour identification as identification was slower when presented with a list of colour related words than when colour neutral words were used.


Our sense organs are constantly being bombarded with vast amounts of information which needs to be processed enabling it to be utilized. Our mind has a limited capacity for dealing with the all of the information it recieves which is why cognitive processes are activated. The cognitive process acts as a filter that selects only the information that is needed for further processing and discards the rest, it is suggested that we do not always have total control over this process. This process is known as selective attention.

Research that has previously been conducted suggested that all information was processed to a certain extent and was known as the 'cocktail party effect'.This was follwed up and resulted in the split-span procedure which was developed by Broadbent (1954 ) it suggested that we have a limited capacity cognitive system and that attention can only be focused on one channel at a time. He conducted a series of dichotic listening tests which involved participants being simultaneously fed seperate numerical information into each ear, the participants were able to recall this information easier from one ear than the other.. He concluded that attention can only be focused on one channel at a time. However, this did not provide an explanation of how the brain is able to cope with more than one task at a time. Kahneman's capacity model (1973 ) took this research further, he suggested that the within the brain was some form of processer that was able to integrate new information with information that had been already stored, concluded that some tasks could be overlearned, therefore requiring only a small amount of processing as they had become automated.

Shiffrin and Schnieder (1977) researched the possibility of automatic processing andthrough a series of experiments were able, to identify some differences between controlled processes which require a large amount of processing resources and automatic processes that occur unconsiously. This discovery led to the devolopment of two-process theories. An example of an automatic task is reading, whilst it is difficult to learn at first, with pratice it eventually becomes automatic requiring no conscious effort.

Stroop's experiment (1935 ) showed that participants had difficulty in naming the ink colour of words that were the names of colours, according to Scriffen and Schneider reading of the words is an automatic process but, to determine the ink colour required controlled processes to be employed.

The reason for this experiment is to determine whether automatic processing interferes with controlled processing in a variation of the Stroop experiment.This is a one-tailed hypothesis. The null hypothesis was that there would not be any difference in the time taken to complete both conditions.


A within -participants design was used for this experiment. Two conditions were employed to represent the independent variable. Condition 1 and Condition 2. Condition 1 consisted of a list of words in colour names and condition 2 was a list of colur neutral words. The dependant variable was the time taken to name the ink colours. In both conditions the participants had to name which colour ink the words on both lists were written in by giving a verbal response.The participants response to each list was timed using a stopwatch and recorded to the nearest second. To counteract possible confounding variables the order in which the conditions were used were changed to avoid a possible practice effect and the same number and colours of the words were used in each list as the time taken will depend on this. Some inks may stand out more than others.


Twenty participants agreed to take part in the study. Sixteen of the participants were recruited by the Open University from amongst work colleagues, family or friends. The remaining four were recruited by myself and consisted of neighbour,s and friends. The age range of the participants was from 18 to 69 years and consisted of fourteen females and six males. To the best of my knowledge all participants were naive to the hypothesis, fluent speakers of English, did not suffer with visual impairment or colour blindness or dyslexia. Consideration was given to the BPS Ethical guidelines and it was concluded that this experiment was within them and that there would not be any breach.


The participants were asked to sit at a table in a well lit room so that the colours were clearly identifiable. A mobile phone stopwatch application was used to time how long it took each participant to complete each task to the nearest second. Two lists of words were used, each containing 30 words split into two columns of 15 using A4 sheets of paper.. The first list consisted of 30 words that were colour related, i.e, Sky. The second list comprised of 30 words that were colour neutral, i.e. Sty.The words in both lists were written in one of 6 different colours which were used in the same order for each of the lists..There were 6 words in total on each list and each word was used 5 times and were randomised. A response sheet containing the participants age, gender, particiapant number and time taken for the test was drawn up to record the data collected. The word lists used are provided in Appendix1. Standard instructions were given to each participant and each gave their consent by completing a consent form (Appendix2).


Each of the parcipants selected were asked if they were prepared to take part in a cognitive psychology experiment and advised that the experiment would take between 5 and 10 minutes. All of the participants who agreed to take part were asked to read and then sign a consent form. The participants age and sex were recorded onto the respone sheet against a participant number i.e, participant 1, 2 etc. and they were informed of what was going to happen during the experiment.Instructions for the test were read out to the participants. They were told that they were going to be tested individually and that they would be provided with two sheets of paper during the test, each sheet containing words printed in colour inks and that they were being asked to say out loud the colour of ink each word was written in the fastest time possible. After the fisrt sheet had been completed there would be a 1 minute delay before starting the second sheet. Each participant was asked if they clearly understood what was being asked of them. The task was then started, each participant was first given one sheet of paper facedown containing either condition 1 or condition 2, they were then asked to turn over the paper and start the test. As soon as the paper was turned the stopwatch was started and their response time was recorded to the nearest second, followed by the second sheet which was recorded in the same way.. The order that the sheets were given out were randomised but it was ensured that each participant took both condition 1 and 2. When both tests were completed the participant was fully debriefed and asked if they had any questions.


The research hypothesis in this experiment was that the participnats would take longer to complete one of the condtions than the other. The results in the Table (Appendix 3) show the mean response times for Condition 1 were 2.50 seconds longer than those for Condition 2. A paired samples t-test was used to analyze the collected data, this has shown that there is a significant difference between the response times between the two conditions (t (19) = 4.430, p = .000, d = 0.648, base on this result the null hypothesis was rejected.


The results of this experiment provide evidence that the time taken to read a list of colour related words was significantly increased when compared to reading a list of colour neutral words. This is consistent with the reaseach hypothesis of the experiment and the experiment by Stroop (1935). Stroop conducted his experiment on 100 people so the sample size for this experiment is significantly smaller, although the results demonstrate similar findings. These findings contradict Broadbent's and other 'bottleneck' theories because if attention can only be focused on one channel, there would be no conflict with information on a second channel as it would be ignored. The results indicate that processing was occuring at an unconscious level which is in keeping with Kahnaman,s theory that tasks could be overlearned and therefore become automated requiring little use of available cognitive processes. The strongest relationship that the results of this experiment has to cognitive processing theories is the theory of Shiffrin and Schneider. They suggested that tasks could become so automatic that any intrusion attempt would not be given priority over automated tasks, Reading is said to be an overlearned task, when presented with a list of words automatic processing occurs, for example, we try to work out the meaning of the words without having to consciously think about what has to be done. During the experiment participants were presented with a list of words and would have automatically tried to work out the meanings of the words, however, they were asked not to interpret the words but, to just name the colour of ink they were printed in. As the results show this task was found to be more difficult, especially when the word was not related to the colour. The reason for this is that although they knew that they had to name the colour of the ink, the automatic process of interpreting the meaning of the word was already active, this then required extra processing resources to be employed. The automatic process was in conflict with the conscious effort of naming the ink colour, this is reflected in the times recorded, the participants were slower when required to provide more attention to naming the ink colour.