Sperry (1968) Flashcards
What is epilepsy?
the tendency to have recurrent seizures which are caused by sudden bursts of excess electric activity in the brain
What does excess electric activity in the brain cause?
temporarily disruption to normal messages passing between nerve cells so that they become halted or mixed up
How is epilepsy usually treated?
medication to prevent the seizures - severe cases where medication does not work a procedure called ‘split-brain’ is carried out
What is a ‘split-brain’ procedure?
when a laser severs the corpus callosum and the connections between the two hemispheres
What is the purpose of the ‘split-brain’ procedure?
any seizure will be contained in only one hemisphere of the brain and people will have an absent seizure - causing less physical damage
What is a ‘split-brain’ procedure a replacement for?
a frontal lobotomy - removal of frontal lobe
What was Sperry’s aim?
to study the effects of hemisphere disconnection (‘split-brain’)
What did Sperry aim to prove?
show that each hemisphere has a different function - lateralisation of functioning
What was Sperry’s sample?
11 ‘split-brain’ patients who had advanced history of epilepsy that could not be treated by medication
What are strengths of the sample?
- had both males and females (no gender bias)
What are weaknesses of the sample?
- small = unrepresentative = lacks population validity = ungeneralisable results
What was the sampling technique did Sperry use?
Opportunity sampling
What are strengths of this technique?
- easy to obtain
What are weaknesses of this technique?
- likely to be the same type of people (not a lot of variation)
What was the method?
Quasi-experiment
What made this study a quasi?
having a ‘split-brain’ is the IV which is naturally occurring
What are strengths of the method?
- no researcher bias
- more ecologically valid
What are weaknesses of the method?
- cannot be generalised to people who the IV does not apply to (only a certain population)
What can this study also be considered?
a case study
Why can this study be considered a case study?
it studies a small group of people and testing them multiple times over a period of time + collecting lots of qualitative data
What is the IV?
having ‘split-brain’
What is the DV?
performance on the visual and tactile tasks
What did the DV aim to demonstrate?
lateralisation of functioning
What was the apparatus used in the procedure?
tachistoscope
What was the set up for the participants?
- wore an eye patch on one eye
- sat in front of a screen with hand holds
- covered hands
- asked to fixate on a black cross in the middle of the screen
What are the 3 types of media used?
- images
- words
- objects
What was standardised about the types of media used?
- same difficulty to identify
- same time to process
- same experimenter used
Why is standardisation a strength?
- it makes the study replicable therefore results more reliable
- causality can be established therefore more valid
What are the two types of tasks?
visual & tactile
What are the key components of the visual tasks?
- images flashed
- 35 millimetre transparencies
- standardised projector
- 1/10th of a second
- either LVF or RVF
- other eye covered
What two symbols were participants shown?
’?’ or ‘$’
Which visual field was presented with each symbol?
’?’ = LVF
‘$’ = RVF
What were participants required to do for the ‘?’ symbol?
asked to name what they saw
What did participants do if they could not complete the task for the ‘?’ symbol?
asked to draw what they saw with their left hand
What were participants required to do for the ‘$’ symbol?
asked the same questions as previously
What happened if the participants could complete the first task?
they were not asked to draw what they saw
What were some participants shown and asked to do?
’?’ to their LVF and ‘$’ to their RVF - asked to name AND then draw with left hand
What was the main component of the tactile task?
having an object placed in either the left or right hand
What object was placed in the participants left hand?
a key
What object was placed in the participants right hand?
tennis ball
What were participants asked?
to name what was in their hand
What did participants have to do if they could not name the object?
given a grab bag and asked to select the item with their left hand amongst other items
What were the visuo-tactile tasks?
combined seeing an image and picking an object
What is an example of a visuo-tactile task?
having the word key shown to the LVF and the word ring to the RVF and asking participants to say what they saw and select the object
What were the key findings for the visual tasks and the ? symbol?
- when ? shown to LVF they could not identify seeing it and would say they did not know what it was
- able to draw it with left hand
- after seeing drawing they could name it
What is the explanation for the LVF and the ? symbol?
LVF is processed by right hemisphere and there are no language areas located there to be able to name what they saw
What are the key findings for the visual task and the $ symbol?
could easily name when shown to RVF
What is the explanation for the RVF and the $ symbol?
processed by left hemisphere where there are language areas
What were the key findings for the participants who were shown a ? to their LVF and a $ to their RVF at the same time?
would have seen $ but draw ? with their left hand
What is an explanation for the combined visual task?
- RVF is being processed by left hemisphere containing language allowing participant to name the $ symbol
- LVF is being processed by right hemisphere doesn’t have language areas and can’t name the ? symbol
- right hemisphere controls left hand it can get it to draw what it saw
What would participants have done if they were asked to draw with their right hand?
$ - controlled by left hemisphere and processed info from LVF
What are the key findings of the tactile tasks in terms of the key ?
- when given a key in their left hand - could not identify
- when given grab bag of objects - left hand is able to retrieve object
What are the key findings of the tactile tasks in terms of the tennis ball?
easily able to name what it was in their right hand
What are the key findings of the tactile tasks when both hands were used?
given grab bag hands acted independently and retrieve correct items
What are the key findings of the tactile tasks and using both hands in relation to split-brain?
able to complete quicker - likely due to the lack of communication between the two hemispheres
What are the key findings of the visuo-tactile tasks?
- when the word key shown to LVF and ring to the RVF participant would pick up key but say they saw the word ring
What is the explanation of the visuo-tactile tasks and the key and ring?
- information of ring in the RVF is processed by the left hemisphere - language = can say what word they saw
- key in LVF is processed by right hemisphere - no language = cannot name but can select (right hem controls left hand)
What are the conclusions drawn about this study?
- the left hemisphere is responsible for language
- left hemisphere controls right side of the body
- right hemisphere is responsible for creative tasks
- right hemisphere controls the left side of the body
- there is a lack of cross integration
- the two hemispheres have own stream of consciousness
What type of data did Sperry collect?
qualitative data
How can you tell its qualitative data?
- not numerical
- says how it demonstrates lateralisation of functioning
What is a strength of qualitative data?
provides explanations and the ‘why’ behind behaviour
What is a weakness of qualitative data?
- subjective
- not easy to analyse or compare
