Split-Brain Research (Biopsychology)

Question 1

Gazzaniga (1970)

Answer 1

Hemispheric lateralisation refers to the dominance of one hemisphere of the brain for particular physical and psychological functions. Each side of the brain is responsible for the opposite side of the body.

The two hemispheres are joined by the corpus callosum

Gazzaniga split the brains of monkeys
-found that, apart from their vision they were unimpaired. They struggled to complete visual tasks using their left eye, although they could complete them with the right eye.

Question 2

Sperry 1968

Answer 2

11 individuals who had undergone a commissurotomy (removal of corpus callosum and surrounding tissue) due to severe epileptic seizures

while patients couldn’t attach verbal labels to objects projected in the left visual field, they were able to select a matching object from a grab-bag of different objects using their left hand
the objects were placed behind a screen so as not to be seen
the left hand was able to select an object that was most closely associated with an object presented to the left visual field
in each case the patient was not able to verbally identify what they had seen but could ‘understand’ that the object was using the right hemisphere and select the corresponding object accordingly

(refer to diagram in notes)

Question 3

(Evaluations for split-brain research) Demonstrated lateralised brain functions

Answer 3

the research was ground-breaking and produced impressive findings
research into the split-brain phenomenon appears to show that the left hemisphere is more geared towards analytic and verbal tasks, while the right is more adept at performing spatial tasks and music
the right hemisphere can only produce rudimentary words and phrases but contributes emotional and holistic content to language

left hemisphere = analyser
right brain = synthesiser

Question 4

(Evaluations for split-brain research) Strengths of the methodology

Answer 4

experiments used highly specialised and standardised procedures
the method used was ingenious, typically participants would be asked to stare at a given point, the fixation point, whilst one eye is blindfolded
the image projected would be flashed up for 1/10 of a second, meaning the split brain patient would not have time to move their eye across the image and so spread the information across both sides of the visual field and both sides of the brain
Sperry was able to develop a useful and well-controlled procedure based off the original research

Question 5

(Evaluations for split-brain research) Theoretical basis

Answer 5

Puncetti (1977) has suggested that the two hemispheres are so functionally different that they represent a form of duality in the brain- that in in effect we are all two minds and that this is a sitation that is only emphasised rather than created in the split brain patient

in contrast, other researchers have argued that, far from working in isolation, the two hemispheres form a highly integrated system and are both involved in most everyday tasks

Question 6

(Evaluations for split-brain research) Issues with generalisation

Answer 6

the sample of participants is unusual
there were only 11 who took part in all variations of the basic procedure, all of whom had a history of epileptic seizures
it has been argued that this may have caused unique changes in the brain that may have influenced the findings
some of the participants had experienced more disconnection of the two hemispheres as part of their surgical procedure than others
the control group that Sperry used was made up of 11 people with no history of epilepsy, may have been inappropriate

Question 7

(Evaluations for split-brain research) Differences in function may be overstated

Answer 7

one legacy of Sperry’s work is a growing body of pop-psychological literature that overemphasises and oversimplifies the functional distinction between the left and right hemisphere
although the verbal and non-verbal labels can be usefully applied to summarise the differences between two hemispheres, modern neuroscientists would contend that the actual distinction is less clear-cut and much more messy than this
in the normal brain, the two hemispheres are in constant communication when performing everyday tasks, and many of the behaviours typically associated with one hemisphere can be effectively performing everyday tasks, and many of the behaviours typically associated with one hemisphere can be effectively performed by the other when the situation requires it