Hemisphere controls

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Last updated: April 7, 2019

The ability of the cerebral hemispheres to carry out an asymmetrical task was investigated in left and right-handed males and females. Subjects balanced a dowel rod on the right and on the left index finger while spelling aloud words and remaining silent. Analysis of the data received did not reveal any large differences between the control and the concurrent activity of speaking whilst balancing. If anything the mean times on a whole were slightly greater while performing the concurrent activity. These results suggest that the lateralisation of function of the left and right hemispheres of the brain do not have a great interference with each other.

IntroductionHumans evolved so that each hemisphere controls the contralateral side of the body. The two hemispheres, although seem to be mirror images of each other physically, do not function exactly the same as one another. In order for both of the hemispheres to work at the same time and function normally the brain performs an asymmetrical task called lateralisation of function.In most humans the left hemisphere of the brain controls most of the functioning of the right side and is also involved with the specialisation of language. Whereas the right hemisphere which controls more of the left side of the body is involved with spatial organisation. Therefore damage to the left hemisphere is usually related to difficulties with speech and language (Davis and Wada, 1977). And damage to the right hemisphere can lead to problems associated with expression and the comprehension of visual patterns (Kalat, 1998).

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Research evidence has shown that when the human brain is tasked to process two separate pieces of information simultaneously which involves the same cerebral hemispheres there is an interference which occurs resulting in a loss of ability to carry out a particular task competently (Kinsbourne and Cook, 1971).If the brain is to perform a concurrent activity which involves the use of just one of the cerebral hemispheres; such as balancing a dowel rod on the right hand and spelling a word, which are both controlled by the left hemisphere in most right-handers, then we should note an interference within the hemisphere to carry out both of the tasks simultaneously resulting in a decrease in time that the subject can balance the dowel rod. If the same verbal task is carried out but using the left hand to balance the dowel rod, remembering that the left hand is controlled by the right hemisphere and plays a small part in language specialisation, then there should be little interference between the asymmetrical task. It should also be noted that for some left-handers language specialisation is not concentrated in just the left hemisphere. Therefore when performing concurrent activities involving both the hemispheres the lateralisation of function is less noticeable.Materials and MethodsSubjectsThere were sixteen normal subjects used for this experiment.

Eleven of which were female and were all right-handed dominant. And of the males four were right-hand dominant and one was left-hand dominant. There was no pre set criteria for the subjects to be in the experiment apart from the fact that they were all in the class.

There was no prior practising of the task involved in the experiment.MaterialsA wooden dowel rod was used for the unimanual balancing task, measuring approximately 30centimeters long and 1.5centimeters in diameter. For each verbal trial one word from a list of words provided by the tutor was used. A stopwatch calculated the time and to record the data on paper a pencil was used.ProcedureIn a standing position, subjects balanced the dowel rod on the right index finger. The timing started from the moment the subjects began to balance the dowel rod until it fell or touched another part of their body. They then proceeded to repeat the process on the right index finger another four times so that a total of five timed results were recorded.

The experiment was then repeated on the left index finger and the results also recorded. These results obtained were to act as the control for the experiment.The same task of balancing the dowel rod on the left and right index fingers was then repeated but the subjects had to also participate in a concurrent activity of spelling aloud a particular word. If the subject continued to balance the dowel rod after spelling aloud the designated word then another word was immediately given to the subject to spell. Once again the five timed results on each of the fingers were recorded.A trial would conclude if the balancing time reached 30 seconds. (None did.

)ResultsThe results were collated into three different groups. These groups being: left-handed dominant males, right-handed dominant males and right-handed dominant females, (there was no left-handed dominant female group because there were none in the class). The mean of times for each trial was then calculated and plotted on a graph (Table 1).Analysis of the mean times for left and right-handed males and females in the non-verbal condition showed no significant variations. Whereas analysis of the mean times for right-handed males balancing the dowel rod on the right index finger whilst speaking showed a slight increase of approximately one and a half seconds compared to the results obtained while not speaking. Right-handed females and the one left-handed dominant male showed no significant variation between the verbal and the non-verbal task.DiscussionBefore starting the experiment many people thought the balancing of the dowel rod without speaking might have enabled you to concentrate more on the task at hand.

The brain and more importantly the left hemisphere was only carrying out the one unimanual task and therefore putting all the focus on balancing the rod. When the task involved speaking as well as balancing there should have been an interference with the brain processing the information asymmetrically but it seemed to have no significant effect on the outcome. Contrary to the experiment hypothesis, the concurrent verbalization slightly enhanced dowel balancing on the right index finger for right-handed males.

It did not enhance the time by much, in fact only one and a half seconds was the recorded increase. The results also reveal that being left or right-handed, male or female did not make any significant differences in how long the dowel rod was balanced.While carrying out the experiment there were many extraneous variables that were not controlled or eliminated. They could have had an effect on the unpredicted results. For example, one of these extraneous variables was that while carrying out the experiment there were other people close around you doing exactly the same thing.

You could have been standing there balancing the dowel rod and out of nowhere another dowel rod comes flying in front of you. This was because there was limited space for each individual to carry out the experiment. Another factor might have been to do with the timing side of the experiment. Was the stopwatch started at the exact time the balancing began? Or; was the stopwatch stopped at the exact time the dowel rod fell? And what interpretation did people put on the word fall? Fall, to some people might have meant when the dowel rod hits the floor. What happens if the dowel rod is flicked into the air before it hits the ground? Do you include those seconds it is flying through the air? Another factor that I think might have influenced the results was to do with practice.We did not practice the balancing of the dowel rod prior to starting but after the initial trials in the non-verbal state I had discovered how to react to the overbalanced dowel rod.

When I first found myself overbalancing the dowel rod I would make hasty adjustments in the opposite direction to get the dowel rod back to the upright position. After a while I discovered that making hasty and quick movements to correct my errors was wrong and that slow and not to sudden movements was keeping the dowel rod balanced for longer. I only came up with those corrections in my balancing in the latter part of the experiment when I was carrying out both the verbal and the balancing task. So due to that practicing in the initial stages of the experiment I increased my times in the latter stages when there should have been a reduction in time. Discussion with other people who did the experiment found that to be the case as well.Though the results contradict the predicted outcome, it is still known that when the cerebral hemispheres are in competition with each other to assimilate certain information there is sometimes an interference with the lateralisation of function resulting in an inefficiency to carry out a particular task.

If the experiment we had conducted was carried out in an environment where all the variables could have been controlled I believe the results would have been a little different and would have backed up the initial predictions.

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