Sperry Flashcards
What was the aim of Sperry’s study?
To test the effects of hemispheric deconnection in human. Specifically to investigate whether cognition, including perception and memory, differs between the hemispheres, and the extent to which the hemispheres would normally interact to achieve these cognitive functions
What was the method, design, IV and DV of Sperry’s study?
Method- Quasi experiment in a Lab setting with control over specific variables (some tests were conducted as comparisons between the left and right hemispheres and these were experimental in method)
Design- Repeated measures design.
IV-Manipulating the hemisphere
DV-Measuring the effect on the individual’s performance in tests of cognition.
Describe the sample in Sperry’s study
Consisted of 11 ps with epilepsy (included at least 1 women).
They has all had an operation to divide the brain in half down the ‘middle’ along the corpus colossum to reduce the spread of epileptic seizures from one side to another.
They had all had severe seizures that could only be controlled with an operation for a long time.
They were evaluated at various times up to 5.5 years post-operatively.
What did the operation do in Sperry’s study?
It cut through the entire corpus callosum, the anterior commissure, hippocampus commissure and, in some patients, also the teh massa intermedia. The effect of this was to disconnect the two halves of the brain, thus preventing exchange of information between the left and right hemispheres.
What was the general procedure of Sperry’s study?
To expose one or both hemispheres to a stimulus and elicit a response. Stimuli were visual, tactual or auditory. Each test began by fixing the gaze on the centre line of the screen and presenting stimuli for precisely measured durations.
What were some controls employed in Sperry’s study?
Covering the non-tested eye, presenting the stimuli to the LVF or the RVF separately.
Presenting stimuli for one-tenth of a second.
Why was stimuli only presented for a short and precisely measured duration in Sperry’s study?
To ensure that the time available would be insufficient for the ps eye to move to view the stimulus in the ‘other’ visual field.
What was the procedure and results for ‘recognition of visual stimuli presented to the left and right hemispheres seperately’ for Sperry’s study?
A picture was flashed to either the LVF or the RVF. The p was shown the image again to either the same or other visual field and asked whether they recognised the object.
Results showed that pictures of objects were recognised only if they were re-flashed to the same visual field.
What was the procedure and results for ‘recognition of visual stimuli presented to the left and right hemispheres seperately’’ for Sperry’s study?
Two different figures were presented to the LVF and the RVF. The ps drew what they had seen with the left hand (hidden from view). They then said what they had drawn, without looking.
Results showed that ps could draw what they had seen in the LVF, but then asked what they had drawn said whatever had entered the RVF.
What does the RVF control and what does the LVF control?
R-Speech, writing, main language centre, calculation.
L-Spacial, construction, simple language, comprehension, nonverbal ideation
What were the 6 different tasks in Sperry’s study?
1) recognising pictures.
2) Matching pictures
3) $ and?
4) composite words i.e Key Case.
5) Identify objects in hand or found from grab bag
6) Dual processing task.
What was the procedure and results for ‘Verbal identification of objects placed in the hand’’ for Sperry’s study?
The p was asked to say or write the name of an object they were holding, or to retrieve and object they had held.
Results showed taht only objects held in the right hand can be named (in speech or writing). Objects held in either hand can be retrieved either immediately or after a delay, but only by the same hand.
What were the 2 main conclusions given for Sperry’s study?
1) In split brain patients , perception in each hemisphere is independent. Information from one visual field or hand passes to only one hemisphere and is not available to the other hemisphere. If the information passes only to the right hemisphere, the individual cannot respond in speech or writing.
2) In split- brain patients, memory in each hemisphere is independent. information from one visual field or hand is remembered only by that hemisphere cannot be accessed by the other.
Outline one problem with generalising from the sample used in sperry’s study
The extent of deconnection would vary between patients.
There are gender differences in lateralisation of function (especially in terms of language), which would be important in terms of generalisability.
Generalisability to the whole population may be invalid due to the restricted (niche) sample, particularly as epilepsy is a brain disorder and finding relate to brain function.
What are the assumptions of the biological perspective?
The area of biological psychology attempts to understand people by assuming they are biological ‘machines’ and that genes, structure of the brain, neurochemistry and endocrine system have a direct influence on behaviour.
It is therefore biologically deterministic. I.E It proposes that behaviour is determined by biological factors and not due to our own free choice or free will.
