Lateralisation and split-brain research Flashcards
(13 cards)
What is hemispheric lateralisation?
Refers to the fact that some mental processes in the brain are mainly specialised to the left or right hemisphere
What is the left hemisphere dominant for?
Language and speech production
What is the right hemisphere dominant for?
Visual-motor tasks
How did Broca’s study lead to the idea the left and right hemisphere were separate?
He found that damage in a particular area of the left hemisphere led to language deficits, yet damage to the same area of the right hemisphere did not have the same consequence
How do the left and right hemisphere communicate?
Two hemispheres are connected by bundles of nerve fibre called the corpus callosum
Who conducted the first split-brain research?
Sperry and Gazzaniga
What is split-brain research?
Studies individuals who have been subjected to the surgical separation of the 2 hemispheres - patients who have had their corpus callosum cut (typically to prevent epileptic seizures)
What was Sperry and Gazzaniga’s study?
A visual task was used where images or words were flashed to either the left visual field (LVF) or right visual field (RVF) while the participant’s head was fixed to prevent eye movement
Because each hemisphere processes information from the opposite visual field, the left hemisphere (which controls language in most people) received input from the RVF, and the right hemisphere from the LVF.
What were the findings from split-brain research?
RVF (left hemisphere): Patients could name and describe objects seen.
LVF (right hemisphere): Patients could not name objects but could select related objects by touch (with the left hand) - suggests the right hemisphere understands the image/word but cannot express it in words
This demonstrated lateralisation of function:
The left hemisphere is dominant for language.
The right hemisphere is better at spatial and visual tasks but lacks language capability.
What is the main strength of hemispheric lateralisation?
It increase neural processing capacity
By using only one hemisphere to engage in a particular task, this leaves the other one free to engage in another
HOWEVER, despite this assumption there is little empirical evidence to suggest lateralisation confers any advantage to the functioning of the brain
Although: Rogers et al found in the domestic chicken - brain laterisation is associated with an enhanced ability to perform two tasks simultaneously
Why is hemispheric lateralisation an oversimplified topic?
Many tasks (like language or reasoning) involve both hemispheres working together.
Modern brain imaging (e.g. fMRI) shows greater integration and interconnectivity than Sperry suggested.
What is an issue with the sample of split-brain research?
Small and unrepresentative sample:
Most participants were epilepsy patients who had undergone major surgery, so findings may not apply to people with typical brains (low population validity) + confounding factors that wouldn’t affect a ‘typical’ brain
Why does the research lack ecological validity?
Tasks such as flashing images to one visual field are not reflective of real-life processing, which limits ecological validity
