split brain research
, Discuss split-brain research (HEMISPHERIC LATERALISATION).
Hemispheric lateralisation refers to the idea that the two hemispheres of the brain are functionally
different, with certain mental processes being mainly controlled by one hemisphere. For example,
language is localised to Broca’s and Wernicke’s areas but lateralised to the left hemisphere. The
left hemisphere controls the right side of the body and vice versa.
Split-brain research by Sperry investigated patients who had undergone a commissurotomy,
severing the corpus callosum to reduce epilepsy. This prevented communication between the
hemispheres. When information was presented to one visual field, only the opposite hemisphere
could process it. Participants could verbally describe objects shown to the right visual field
(processed by the left hemisphere) but not those shown to the left visual field (processed by the
right hemisphere) because language is localised in the left hemisphere. However, they could
identify or match the object using their left hand, showing the right hemisphere understood the
object non-verbally. Sperry also found that the right hemisphere was dominant in recognising faces,
while the left hemisphere specialised in verbal description.
Sample size and generalisability
A major limitation of split-brain research is the very small sample size, often involving only
a handful of epileptic patients who had undergone commissurotomy. This means findings
may not be representative of people with intact brains or even all epileptic patients, as
brain function may have been altered by their condition or medication. Therefore, the
results lack population validity and cannot be easily generalised to the wider population.
2. Reductionist – complexity of brain function
The research is biologically reductionist, as it isolates hemispheric functions and assumes
specific abilities are confined to one side of the brain. In reality, most cognitive processes
(like language or emotion) involve complex interactions between both hemispheres and
multiple brain regions. This oversimplifies how the brain truly operates and may
underestimate integrated neural networks.
3. Differences in hemispheric functions overstated
Some psychologists argue that the differences between hemispheres have been
exaggerated. In a normal brain, both hemispheres constantly communicate through the
corpus callosum, meaning that the division of function is not absolute. For example, verbal
and spatial abilities can often be compensated for by the opposite hemisphere. Thus,
hemispheric lateralisation may be more interdependent than Sperry’s findings suggest.
4. Plasticity and functional recovery
Research into brain plasticity shows that when one hemisphere is damaged, the other
can often adapt or take over some of its functions. This challenges the strict view of fixed
lateralisation, suggesting the brain is far more flexible than split-brain studies imply.
Therefore, Sperry’s conclusions may not apply to how the brain functions in everyday life,
where compensation and reorganisation occur.
, Discuss split-brain research (HEMISPHERIC LATERALISATION).
Hemispheric lateralisation refers to the idea that the two hemispheres of the brain are functionally
different, with certain mental processes being mainly controlled by one hemisphere. For example,
language is localised to Broca’s and Wernicke’s areas but lateralised to the left hemisphere. The
left hemisphere controls the right side of the body and vice versa.
Split-brain research by Sperry investigated patients who had undergone a commissurotomy,
severing the corpus callosum to reduce epilepsy. This prevented communication between the
hemispheres. When information was presented to one visual field, only the opposite hemisphere
could process it. Participants could verbally describe objects shown to the right visual field
(processed by the left hemisphere) but not those shown to the left visual field (processed by the
right hemisphere) because language is localised in the left hemisphere. However, they could
identify or match the object using their left hand, showing the right hemisphere understood the
object non-verbally. Sperry also found that the right hemisphere was dominant in recognising faces,
while the left hemisphere specialised in verbal description.
Sample size and generalisability
A major limitation of split-brain research is the very small sample size, often involving only
a handful of epileptic patients who had undergone commissurotomy. This means findings
may not be representative of people with intact brains or even all epileptic patients, as
brain function may have been altered by their condition or medication. Therefore, the
results lack population validity and cannot be easily generalised to the wider population.
2. Reductionist – complexity of brain function
The research is biologically reductionist, as it isolates hemispheric functions and assumes
specific abilities are confined to one side of the brain. In reality, most cognitive processes
(like language or emotion) involve complex interactions between both hemispheres and
multiple brain regions. This oversimplifies how the brain truly operates and may
underestimate integrated neural networks.
3. Differences in hemispheric functions overstated
Some psychologists argue that the differences between hemispheres have been
exaggerated. In a normal brain, both hemispheres constantly communicate through the
corpus callosum, meaning that the division of function is not absolute. For example, verbal
and spatial abilities can often be compensated for by the opposite hemisphere. Thus,
hemispheric lateralisation may be more interdependent than Sperry’s findings suggest.
4. Plasticity and functional recovery
Research into brain plasticity shows that when one hemisphere is damaged, the other
can often adapt or take over some of its functions. This challenges the strict view of fixed
lateralisation, suggesting the brain is far more flexible than split-brain studies imply.
Therefore, Sperry’s conclusions may not apply to how the brain functions in everyday life,
where compensation and reorganisation occur.
