Biopsychology - Hemispheric Lateralisation

Question 1

What is lateralisation?

Answer 1

Lateralisation is the idea that the two halves of the brain are functionally different and
that each hemisphere has functional specialisations, e.g. the left is dominant for
language, and the right excels at visual motor tasks.

Question 2

How do the brain hemispheres communicate?

Answer 2

The two hemispheres are
connected through nerve fibres called the corpus callosum, which facilitate
interhemispheric communication: allowing the left and right hemispheres to ‘talk to’
one another

Question 3

What are split-brain patients?

Answer 3

Split-brain patients are individuals who have undergone a surgical
procedure where the corpus callosum, which connects the two hemispheres, is cut. This
procedure, which separates the two hemispheres, was used as a treatment for severe
epilepsy.

Question 4

Describe Sperry and Gazzaniga’s experiment

Answer 4

Sperry and Gazzaniga (1967) were the first to investigate hemispheric lateralisation
with the use of split-brain patients.

Aim: The aim of their research was to examine the extent to which the two
hemispheres are specialised for certain functions.

Method: An image/word is projected to the split-brain patient’s left visual field (which is
processed by the right hemisphere) or the right visual field (which is processed by the
left hemisphere). When information is presented to one hemisphere in a split-brain
patient, the information is not transferred to the other hemisphere (as the corpus
callosum is cut).
Sperry and Gazzaniga conducted many different tasks. For example, in the drawing task, participants were presented with a picture in either their left or right visual field, and they had to simply draw what they saw.

Conclusion: The findings of Sperry and Gazzaniga’s research highlights a number of key
differences between the two hemispheres. Firstly, the left hemisphere is dominant in
terms of speech and language. Secondly, the right hemisphere is dominant in terms of
visual-motor tasks.

Question 5

Evaluate split-brain research - multiple tasks

Answer 5

It is assumed that the main advantage of brain lateralisation is that it increases
the ability to perform multiple tasks
simultaneously.
Rogers et al. (2004) found that in a domestic chicken, brain
lateralisation is associated with an enhanced ability to perform two tasks
simultaneously (finding food and being vigilant for predators). Using only one
hemisphere to engage in a task leaves the other hemisphere free to engage in
other functions.
This provides evidence for the advantages of brain
lateralisation and demonstrates how it can enhance brain efficiency in
cognitive tasks.

Question 6

Evaluate split-brain research - Turk

Answer 6

It could be argued that language may not be restricted to the left
hemisphere.
Turk et al. (2002) discovered a patient who suffered damage to the
left hemisphere but developed the capacity to speak in the right hemisphere,
eventually leading to the ability to speak about the information presented to either
side of the brain. This suggests that perhaps lateralisation is not fixed and that the
brain can adapt following damage to certain areas.