Hemispheric Lateralisation and Split Brain

• Hemispheric Lateralisation:

  :) RTS Sperry

  > split brain patients with a severed corpus collosum

  > when participants were shown an image of an object to their right visual field, they could name it verbally, but when presented to the left visual field, they could only identify it through pointing

  > supports that the brain is lateralised and the hemispheres are responsible for different functions, so supports hemispheric lateralisation

  discussion - individual differences (degree to which corpus collosum was severed varied - reduces internal validity)
• Hemispheric Lateralisation:

  :( RTC patient EB

  > suffered from brain damage that resulted in the removal of his left hemisphere, and therefore his language centres, but after some time, he managed to regain some language ability - would not be possible if the brain was completely lateralised

  > argues against lateralisation of function

  discussion - lacks population validity
• Split Brain Research:

  :) scientific methods

  > based on objective and empirical techniques, such as controlled lab environments

  > used to identify which hemisphere of the brain is responsible for which task e.g. patients were only able to verbally identify the object when it was presented to the right visual field, suggesting that the left hemisphere is activated during language tasks

  > increases internal validity and raises psychology's scientific status
• Split Brain Research:

  :( individual differences

  > the degree to which the corpus callosum was severed for each participant varied greatly - some had greater disconnection

  > reduces internal validity
• Split Brain Research:

  :( causal relationship is hard to establish

  > the split brain participants were compared to a neurotypical control group - none had epilepsy

  > may act as a confounding variable, as any differences between the two groups may have been due to epilepsy rather than the split brain - difficult to establish whether cognitive abilities and lateralisation are due to split brain or epilepsy

  > lowers internal validity
• Split Brain Research:

  :( RTC patient EB

  > suffered from brain damage that resulted in the removal of his left hemisphere, and therefore his language centres, but after some time, he managed to regain some language ability - would not be possible if the brain was completely lateralised

  > argues against lateralisation of function