Lateralisation and split brain research Flashcards
What did Sperry want to find out? (1968)
If hemispheric lateralisation was the same for other functions in the brain
What RPS did Sperry use for his split brain research?
Individuals who had undergone the same surgical procedure - commissurotomy
The corpus callosum and other tissues that connect the two hemispheres were cut in order to control seizures
What was prevented in split brain patients?
Communication between the two hemispheres
What did the use of split brain patients allow Sperry to see?
To which extent the two hemispheres were specialised and whether tasks are performed independently of each other
What is hemispheric lateralisation?
The idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations
What does the right hemisphere control?
Visual motor tasks
What does the left hemisphere control?
language
What is the role of the corpus callosum?
Connects the two hemispheres, allowing communication between the two
What were three of the experiments which Sperry carried out?
- Describe what you see
- Tactile test
- Drawing task
What was the procedure for describe what you see?
A picture was presented to either the left or the right hemisphere and they had to describe what they saw
What happens when the picture is presented to the right visual field?
The patient could describe what they had seen, demonstrating the superiority of the left hemisphere when it comes to language production.
What hemisphere processes the right visual field?
Left hemisphere (language)
What hemisphere processes the left visual field?
Right hemisphere (motor)
What happens when the picture is presented to the left visual field?
The patient could not describe what they had seen, saying that there was nothing present often
What was the procedure of the tactile test?
an object was placed in either the right or left hand and they had to either describe what they felt or select a similar object from a series of other objects in front
In the tactile test, what happened when the object was placed in the left hand? (processed by right hemisphere)
- The patient couldn’t describe what they had felt and could only make wild guesses
- The left hand could identify an object by selecting a similar appropriate object
In the tactile test, what happened when the object was placed in the right hand? (processed by left hemisphere)
- The patient could describe what they had felt verbally
- The patient could also identify an object presented in the right hand by selecting similar objects
What was the procedure of the drawing task?
The patients were presented with a picture or words in front of them in either the left or right visual field and they had to draw what they had seen
What were the findings for the left hand in the drawing task? (controlled by the right hemisphere)
the drawings were consistently clearer and better pictures than the right hand even though they were right handed
What do the findings for the drawings of the left hand demonstrate?
The superiority of the right hemisphere when it comes to visual motor tasks
What were the findings for the right hand in the drawing task? (controlled by the left hemisphere)
They attempted to draw a picture but it was never as clear as the left hand
What are strengths of split brain research?
Highly controlled laboratory research - replicated
What are weaknesses of split brain research?
- very limited sample size (sperry used 11 RPS)
- Patients had epilepsy - limits generalisability to healthy people
What is the main problem of split brain research?
Lacks ecological validity - in real life, patient use both eyes to compensate for the disconnection between the two hemispheres
What is the issue with replication?
Split brain patients are rare
What are the issues with the patients used in Sperry’s research?
- They had epilepsy which means the results have limited generalisability to healthy population
- Some patients were also taking medication
- Surgery was more severe in some patients
- Small sample size used
Does split brain research take an idiographic or nomothetic approach? Why?
Idiographic
Some psychologists argue that Sperry’s research is just a collection of case studies which means general laws cant be created
