Allport (1980) gave the example of people who demonstrate a capacity to handle two inputs at once. E.g. musicians who can shadow a prose message while sight reading music or, subjects who can read letters aloud and add digits. Usually in these types of dual tasks, the subjects are often highly skilled in one of the tasks.
Shriffren and Schneider (1977) said that subjects who can perform two tasks at once are displaying “automatic processing” which is when the stimuli trigger existing sequences of operations in long term memory. These operations do not require attention so there are no capacity limitations for such tasks.
An ideal example of divided attention is demonstrated by the Stroop Effect
(Stroop 1935). He gave subjects a list of colour words printed in different coloured inks (e.g. the word ‘blue’ displayed in red ink) and found that while incongruent colours did not interfere with word reading, incongruent colour words interfered significantly with naming colours. This was indicated by longer response times for colour naming.
The two most influential theoretical explanations for the longer response times are the speed of processing and the automaticity hypotheses.
Speed of processing model, Morton and Chambers (1973) assume that words are read faster than colours can be named, because when information from each dimension conflicts, the word response interferes with the colour response, causing the delay in naming colours.
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The automaticity hypothesis is based on a distinction between automatic and controlled processes. It proposes that reading words is a strongly automatic process which is involuntary and makes no attentional demands, whereas naming colours is a relatively controlled process, subject to conscious intent and requiring attention. When word and colour responses are different, the more automatic process of word reading interferes with and delays colour naming. It is suggested that word reading is more automatic because we have much more experience at it, an explanation which resembles that put forward by Stroop himself.
The studies described are all based on attention, divided attention and the original stroop effect.
The present study is to investigate further into the divided attention theory. It aims firstly to reproduce the basic stroop effect, carefully modified for varied results and then to support the findings of Stroop, Shriffren and Schneider and Morton and Chambers.
It proposes to use shapes and shape words instead of colours and colour words to investigate whether the shapes interfere with the reading of the shape word and if the shape words interfere with the reading of the shapes.
Hypothesis
There will be longer response times when the shapes are read because the shape words will interfere.
Null Hypothesis
There will not be longer response times when the shapes are read because the shape words will not interfere.
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Method
Design
The repeated measures design was used because the sample is only small and to control participant variables e.g. reading speed.
Condition 1 = The colour words were read column by column.
Condition 2 = The shape names were read column by column.
The participants were counter balanced to either condition 1 or condition 2 and were asked to carry out the experiment in a well lit, quiet room with no distractions. The time of day was kept the same and the same stimulus was used for each participant. These controls were kept constant to ensure that there was no bias and that the IV was the only variable that could affect the DV.
IV = The interference of the shape names.
DV = The time taken to name the shape, measured in seconds.
Regarding ethical issues, the participants were not at any time placed in a situation where they felt pressured to take part or continue and were fully aware of the right to withdraw. The investigation was followed up by a thorough debriefing and only necessary information was withheld such as the aim of the investigation so as not to affect their behaviour. Participants were given as much information as was reasonably possible.
Participants
Opportunity sampling was used as it is quick, cheap and it was impossible to get a fully representative sample of the target population. It also gives a fairly unbiased sample when time constraints prevent being able to use a better method such as random sampling. It also ensures that a fairly accurate cross section of different ages, occupations etc. could be sampled rather than limiting the sample to being very small and unknown. There were 8 participants in each condition and the target population was the friends and relatives of the experimenter, in a small town in West Yorkshire. The participants were a mixture of males and females and a range of ages.
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Materials/apparatus
The stimulus consists of three columns of random shapes with the name of a different shape printed inside them. It is printed in black and white and in bold letters to allow the words to be read clearly.
The stop watch was to time how long it took each participant to carry out condition 1 and condition 2. The experiment was timed in seconds.
Procedure
Instructions and explanations to participants:
“Would you like to take part in a psychological experiment? You will be taken to a small quiet room and you have the right to withdraw at any time. You will be given as much information as is reasonably possible and clear instructions of how to carry out the tasks.”
“First of all would you read the printed words aloud column by column. Next if you would read the shape name which surrounds each printed word column by column. The length of time it took for you to complete each task has been recorded.”
“I would like to thank you for taking part. The purpose of these results is to investigate whether the colour words interfered when you were concentrating on reading the surrounding shape. If u took a longer amount of time when reading the surrounding shapes this may be true. This may be because reading is such an automatic action. You will be informed of the overall conclusion at a later date.
Thank you again.”
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Results
This is a table to show the results for an investigation into the stroop effect using words and shapes. The results for condition 1 and condition 2 are based on the amount of time it took for the paticipants to complete the task.
The above table shows:
The no. of participants
The total of the raw results
The average
The most frequent value
The middle value
The difference between the greatest and the least value
Using a table to display the results is an easy way of making a comparison between condition 1 and condition 2. Condition 2 was the condition which took the participants the longest amount of time to complete. ( see appendix for calculations) this supports the theory that the words interfere with the reading of the shapes and the response times are longer.
Treatment of results
By looking at the data there is a big enough difference to say that the IV has affected the DV. I will take up he experimental hypothesis because there are large differences both in the total times taken and the averages. The difference is significant to say that the words did interfere with the reading of the shapes because the response times were longer.
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Discussion and conclusions
The experimenter took up the experimental hypothesis.
There will be longer response times when the shapes are read because the shape words will interfere.
The experiment proves what the original stroop effect proves and the experimenter was right to predict this as the experiment does support background theories by Kahneman and Henik. One of the results did not fit in correctly with the others, which gave an anomolous result. This may have been because the participant was not a good reader or maybe they were less aroused.
The experimenter only had a small unrepresentative sample so the investigation would have been more accurate if the sample was larger and included more representatives of a broader cross section of the population.
If the experiment was to be conducted again a larger sample would be used and closer control over environmental conditions. The shapes could also be changed for something else such as shapes of animals or use numbers. E.g.
3 3 3 3
- 4
6 6 6 6 6
- 3
1 1 1 1 1 1
7 7 7 7 7
5 5 5
2 2 2 2
The participants would have to state how many numbers are in each row. The experimenter would have to investigate whether the printed numbers affected the participant’s ability to state the amount of numbers in each row. This is a similar idea to the stroop effect and would be a good example of a further study.
In conclusion the words did affect the participant’s ability to state the shape therefore the experiment was successful in supporting theories. The experimental hypothesis was correct as supported by the results. The experiment proved that the IV did affect the DV.
References
- The science of mind and behaviour.
By Richard Gross
Published by Hodder and Stoughton
Chapter on attention