Lateralisation and split - brain research

❎✅ for ctrl c+v-------(s)= sperry (l) = lateralisation

The Two Hemispheres

Left Hemisphere

* Language
* Speech

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Right Hemisphere

* Visual Motor
Tasks
* Face Recognition

split brain patients

corpus collosum connects both hemispheres

unique group of patients who had commissurotomy - where corpus collosum is severed so that the two hemispheres are separated and don’t communicate with each other

this is don’t to control frequent and severe epileptic fits

Sperry’s split brain research

* Aim: to show the independent streams of conscious awareness produced by each hemisphere and to show that each hemisphere has its own memories
* method: quasi experiment (independent variable is a condition rather than an actual variable) in lab with independent measures design
* independent variable: whether patient had split-brain or not
* dependent variable: individuals performance on visual and tactile tasks
* control variable: no control as effect f slit brains were already known
* sample: 11 patients - all epileptics that had undergone commissurotomies

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(S) AO3: Quasi (natural experiment)

Controlled conditions - standardized procedures = good internal reliability

(S) AO3: lack of ecological validity

in real life, patients can adjust visual position so information goes to both hemispheres

(S) AO3: fast presentation

meant that the patient didn’t have time to move their eyes across to process the image with the other side

(S) AO3: population validity

sample was 11 - may be too small to generalize. also it may be inappropriate to make generalizations about non-epileptic seizures could have made changes to the brain that could have affected the findings.

(L) AO3: neural capacity

* one of the main strengths is that it can increase neural capacity.
* by using one hemisphere to complete a task, the other hemisphere is free to engage in another function, increasing brain efficiency
* > **Rogers 2004** - found in chickens lateralisation is associated with an enhanced ability to perform two tasks at once - e.g. hunting for food and watching out for predators

(L) AO3: age

* **Szaflarsky et al 2006**
* found language became lateralized to the left hemisphere with increasing age in children and adolescence
* after 25, lateralization decreases with each decade of life

Gazzaniga 1998

* claims some of early discoveries of split brain research has been disconfirmed by recent discoveries
* damage to left hemisphere was found to be far more detrimental to language function than the right
* however, J.W a split-brain patient, developed capability to talk out of right hemisphere, challenging idea that language is restricted to left.

split brain limitations

* split brain procedure is very rare, only in desperate circumstances - such as severe physical disorders
* > therefore, there have been limited numbers to make this research useful