Participants
All of the participants in this experiment were known by the researcher as friends and colleagues. None of the participants was familiar with the hypothesis being tested. They were recruited by asking if they wanted to participate in an experiment. The age of the participants ranged from 18 to 64 years of age and there were 14 female and 14 male (full details of the information obtained is shown in Appendix 4). English was the first language of all the participants and all had normal or corrected-to-normal vision.
Materials
A stopwatch accurate to 1/10th second was used to time how long it took each participant to complete the task. The stimuli presented to the participants consisted of a list of words printed in black ink. Examples of the word lists used in both conditions are provided in Appendix 1. There were a total of 36 words in each list with a box next to each word. The experimental condition (condition 1) consisted of 16 names of numbers presented in a random order. For the control condition (condition 2) the word list contained 16 names of colours also presented in a random order. Each list was presented in two columns on a white piece of A4 paper. Sufficient space was given between each word so that it did not interfere with the words either above or below and there was a box to the right of each word. The list of mathematical questions asked to the participants is provided in Appendix 2.
Procedure
Each participant was approached and asked if they would be prepared to take part in a dual-task psychology experiment that would take between 2 and 5 minutes. The participants who agreed to take part were tested individually. Before explaining what would happen in the experiment, the age and sex of the participant was recorded, as was whether they had any experience of psychology. Every participant was then told that they would be presented with a list of words and they would need to place a tick against the words that were either colours or numbers (depending on which condition they were given). They were told to do this as quickly as they could manage and at the same time as doing this they would need to verbally answer the answers to simple mathematical equations that the researcher asked them (a fully copy of the instructions is provided in Appendix 3). After the participant indicated that they understood the instructions, the list of words was placed face down in front of them. Participant one started with condition one and each condition was alternated with each participant thereafter. The word-list was then turned over, the experimenter started the stopwatch and the participant began to tick the appropriate boxes whist verbally answering the mathematical questions put to them by the experimenter. When the participant had finished the word-list, the experimenter recorded the time taken on a separate response sheet. The participant was then debriefed and asked if they had any questions regarding the experiment.
Results
The experimental hypothesis that was tested in the current experiment was that it would take participants longer to complete two tasks that require similar responses than two tasks that require dissimilar responses. The time it took for each participant to tick the relevant boxes from the lists, whist verbally answering mathematical questions, was measured to the nearest second. All the results recorded are shown in Appendix 4. The mean length of time taken is displayed in Table 1.
Table 1 Mean length of time taken by condition
As can be seen from Table 1, it took longer on average for the participants to tick the boxes of the relevant words in the experimental condition than in the control condition. An independent-samples t-test was conducted on these data, which revealed that the difference between these conditions was statistically significant (t =-.499; df = 26; p =.622). Full details of the independent samples t-test is shown in Appendix 5. On the basis of this result it was possible to accept the experimental hypothesis and to reject the null hypothesis.
Discussion
The results of this experiment showed that whilst verbally answering simple mathematical questions, it took longer for participants to place a tick against the number words (condition 2) as opposed to the colour words (condition 1). There was a greater similarity in the responses for condition 2 because the words being searched for and the verbal responses were both numbers. This suggests that when the brain is performing a dual-task, cognitive resources are limited by the similarity of the stimuli even if two different modes of presentation (visual and auditory) and two different modes of responses (manual and verbal) are used.
Studies carried out by Posner and Boies (1971) (cited by Edgar. G. 2002) suggested that participants had limited resources to process and make a response to two things simultaneously if both the tasks required a manual response (in this case the right hand clicking a button and the left hand clicking a button) when one task was visual (a letter-matching task) and the other was auditory (simply listening for an auditory tone).
However, a later study carried out by McLeod (1977) cited by Edgar. G. 2002) showed that reaction time was not slowed to the same tasks, if the responses required were in separate modes, in this case a button press (manual task) and saying ‘bip’ (verbal task). This implies that either one or more of the tasks is not drawing on the central processor at all or that each task is accessing a separate pool of resources (Edgar, G. 2002). The tasks were different in modality and also unrelated.
The multiple-resource theories of attention (Navon and Gopher, 1979; Wickens, 1992, cited by Edgar. G. 2002) suggest that “different pools of resources are available for different types of tasks” (Edgar, G. 2002) as opposed to all tasks drawing on a single central pool of resources.
In the experiment carried out in this report, the responses required separate modes – in the form of ticking a box (manual) and simple mathematical calculations (verbal) but condition 2 provided a similarity because the words requiring a tick against them were numbers. This provided a common denominator in the form of numbers being present in the manual task and numbers being present in the verbal task and it took longer on average for participants to complete condition 2 compared to condition 1. It has not been established how resource pools are divided and allocated but these results demonstrate the possibility that there may be separate resources for certain types of information (e.g. mathematical) as well as for the type of mode the information is presented in (e.g. manual and auditory) and that pools of resources are not just linked to the response required.
On evaluation of the experiment on the whole there were a couple of problematic areas. The first being that some of the participants did not tick some of the words they were supposed to and this was not taken into account in their response time. As a result they may have completed the task quicker than another participant who had ticked all the relevant boxes and as the results were based solely on the response time, completing the task quicker because of this factor needs to be eliminated. The same is relevant for participants who answered any of the mathematical calculations incorrectly.
One confounding variable that may have affected the results could be the differing mathematical abilities of the participants. A solution to this would be to make the simple mathematical equations (that required a verbal response) much more simple – ones that would warrant more of an automatic response so for example 2 x 6 and 3 x 3 as opposed to 9 x 7 and 8 x 9.
References
Edgar, G. (2002) 'Perception and attention', in Miell, D., Phoenix, A., Thomas, K. (eds) Mapping Psychology 2, The Open University (2002).
Kahneman, D. (1973) Attention and Effort, Englewood Cliffs, New Jersey, Prentice-Hall.
McLeod, P.D. (1977) 'A dual task response modality effect: Support for multi-processor models of attention', Quarterly Journal of Experimental Psychology, vol.29, pp.83-9.
Navon, D. and Gopher, D. (1979) ‘On the economy of the human processing system’, Psychological Review, vol.86, pp.214-55.
Posner, M.I. and Boies, S.J. (1971) ‘Components of attention’, Psychological Review, vol.78, pp.391-408.
Wickens, C.D. (1992) Engineering Psychology and Human Performance (2nd edn) New York, Harper Collins.
Appendix 1
Below is a copy of the word lists that were used in both the experimental and control conditions. To save space the lists have been reduced in size, the original pages were A4.
Appendix 2
Below is copy of the simple mathematical questions that each participant was verbally asked. To save space the list has been reduced in size.
Appendix 3
The following instructions were given to each participant:
Instructions: Experiment 2A, Condition 1
In a moment I will place a sheet of A4 paper n front of you that contains two columns of words. What I would like you to do is to place a tick next to those words that are the name of a colour, e.g. RED or BLUE. Start with the word at the top of the left column and word downwards. When you have finished all the words in the left column start on the right column. At the SAME TIME as you are doing this, I will be asking you a series of simple mathematical questions. I want you to answer each mathematical question as I ask it.
Do you understand what you will be required to do?
(If yes, then proceed to task. If no, go through the instructions again.)
Instructions: Experiment 2A, Condition 2
In a moment I will place a sheet of A4 paper n front of you that contains two columns of words. What I would like you to do is to place a tick next to those words that are the name of a colour, e.g. SEVEN or NINE. Start with the word at the top of the left column and word downwards. When you have finished all the words in the left column start on the right column. At the SAME TIME as you are doing this, I will be asking you a series of simple mathematical questions. I want you to answer each mathematical question as I ask it.
Do you understand what you will be required to do?
(If yes, then proceed to task. If no, go through the instructions again.)
Appendix 4
The following table shows the data collected from each participant:
Appendix 5
The attached sheet is the output for Independent-Samples T Test using SPSS
