A 2-tailed, paired-samples, related t-test was performed on the number of correct responses given by the participants and a significant difference ( t(1,87) = 30.315, p < 0.001), was found between the number of correct responses given between the level of difficulty of the tasks. See Table 2, below. Discussion As can be seen from the results there is clear evidence to show that there is no direct relationship between task difficulty and heart rate.
The results show that there is a highly significant difference (F1,87 = 25.325, p < 0.001) in the mean heart rate between the types of task performed by the participant however they also show that heart rate is not significantly effected (F1,87 = 11.605, p = 0.232) by the level of difficulty of the task. There is, however, a significant interaction effect between the two variables suggesting that there is a relationship between the type of ask preformed and its level of difficulty and together, they affect heart rate. The results from the t-test show that there is a significant difference in the number of correct responses for each task, with the least number of correct responses being in the Hard Mental Arithmetic condition and the most amounts of correct responses occurring the Easy Visual Search condition.
The experimental Hypotheses are therefore accepted; although there is no direct relation ship between heart rate and task difficulty, heart rate can, in fact, change depending on the type of task presented; tasks requiring the rejection of information from the environment (mental arithmetic tasks) were proved to produce a faster heart beat and tasks that required the intake of information from the environment (visual search tasks) were proved to produce a lower heart rate. This supports Lacey’s (1967) Intake-Reject hypothesis that High Mental Arithmetic (HMA) tasks will produce a higher heart rate than Easy Mental Arithmetic tasks (EMA) and High Visual Search (HVS) tasks will produce a lower heart rate in comparison to Easy Visual Search (EVS) tasks.
It is interesting to note that task difficulty has no significant effect on heart rate alone, as this would have been a logical conclusion to come to given that heart rate tends to increase with stress. However, this does support Lacey’s theory that difficult tasks requiring rejection of external information will produce a higher heart rate than easier tasks requiring the same rejection of information. A reason for this could be because these type of tasks much more mental input by ourselves that others and it is possible that participants can anticipate greater mental stress, resulting in an increase in heart rate. Task difficulty also comes into play when dealing with situations requiring the intake of environmental stimuli, with harder tasks producing a decrease in heart rate.
One of the main limitations of this study is that no control was made for the possibility of other factors affecting heart rate, such as stress, illness etc. Participants who may have been suffering from stress-related diseases may have a higher heart rate thus affecting the reliability of the results. The participants were students partaking in a class experiment and may have had previous knowledge that could influence their reactions to the tasks.
For example, if the participant knew we were testing Lacey’s theory and had prior knowledge of the intake-reject hypothesis, they could manipulate their responses, which would affect the validity of the results. Also, the participants, all studying the same course, at the same university, may well have told other participants who had no yet taken the test what to expect. Preparing for the tasks, emotionally as well as mentally, may well have an effect on their performance in the study.
The study conducted gave sufficient results for the research questions, but there are other areas that could be investigated if the study were to be replicated. We would compare different levels of difficulty (more than two) and also different types of tasks that require Intake-Rejection of environmental stimuli comparing them to one another. Also it would be interesting to see if age and gender play a factor in rise and fall of heart rate with specific reference to these types of tasks.
It would be interesting to see if there was a biological difference in the heart rate responses of males and females to type of task given and their performance at various difficulty levels. Furthermore, different populations could be examined, testing for any possible cultural differences that may have an effect on heart rate during problem solving. As mentioned above, it may also be an idea to test to see if preparation for the tasks has any effect on heart rate during performance, if the participants know what to expect from the tasks, their physiological responses may differ from when they do not know what to expect.
In conclusion this study has indicated that although there is no direct relationship between task difficulty and heart rate, levels of difficulty with the types of task performed do have an effect on heart rate, as do the types of tasks. This supports Lacey’s Intake-Reject Hypothesis suggesting that heart rate can, in fact, change depending on the type of task presented; tasks requiring the rejection of information from the environment (mental arithmetic tasks) were proved to produce a faster heart beat and tasks that required the intake of information from the environment (visual search tasks) were proved to produce a lower heart rate.
References:
Hahn, W.W. (1973). Attention and heart rate: A critical appraisal of the hypothesis of Lacey and Lacey. Psychological Bulletin, 79: 59-70.
Lacey, J.I., (1967). Somatic response patterning and stress: Some revisions of activation theory. In: M.H. Appley and R. Trumbull (Eds). Psychological Stress: Issues in Research. New York: Appleton Century Crofts, pp 14-37.