A-level psychology: Sperry

biological approach split brain study

what does it mean to have a split brain?

when a persons corpus collosum is severed and the two hemispheres of the brain is split in order to control the abnormal electrical discharges that causes epileptic seizures

what is the biological approach/ area?

it believes that behaviour is shaped by psychological causes and assumes that psychology should study the brain, nervous system etc to explain behaviour

what hemisphere is the right visual field connected to?

left hemisphere

what hemisphere is the left visual field connected to?

right hemisphere

what hemisphere controls speech and language?

the left hemisphere

what is a commissurotomy?

the severing of the corpus callosum

what was the aim of sperry's study?

to show the independent streams of conscious awareness from each hemisphere and how each hemisphere has its own separate memories

what was the method used in the study?

quasi experiment (naturally occurring IV in an artificial setting)

what year did the study take place?

1968

what was the sample used in the study?

11 patients who had split brain

• a man who had surgery over 5 1/2 years before

• a housewife and mother in her 30s who had surgery more than 4 years before

• the other 9 patients had their surgery at varying times not long before the study

why would sperry's study be considered a case study?

the sample was relatively small

what was the IV in the study?

whether the patient had split brain

what was the DV in the study?

the patients ability to perform a variety of visual and tactile tasks

why was there no control group in the study?

no control group as the effects of not having a split brain as already known

what measure design was used in the study?

independent measure design

what was the procedure for the visual tasks?

Sperry used a tachistoscope which had a focal point in the middle and two areas where the stimuli was presented. The participants would have one eye covered and were instructed to stare at the focal point.

how long was the stimuli shown on the screen and why?

it was shown for 0.1 seconds and it was a control as it was too quick for eye movements to take in the information from both visual fields.

why did the participants have to cover one eye?

this was a control to ensure that the stimuli was only shown to the desired visual field

what was the $ and ? task?

where both the $ and ? was presented simultaneously (one to the right visual field and the other to the left visual field). participants were then tested on the stimuli

what were the findings from the visual task?

sperry found that information that was shown to the left of the focal point would be seen in the left visual field and then processed in the right hemisphere

he also found that participants could only say what they saw when the stimuli was shown to their right visual field and processed in their left hemisphere- showing that language is dominant in the left

when different figures such as $ and ? were shown simultaneously eg- $ to the left visual field and ? to the right visual field, the participant could draw the $ sign with their left hand but had said they had seen a ?

what was the procedure for the tactile task?

the participants would put their hands under the tachistoscope where there would be objects present. their hands were covered and they were introduced to different objects by an experimenter who placed them in their hands.

what hemisphere was an object processed if it was placed in their right hand?

the left hemisphere

what hemisphere was an object processed if it was placed in their left hand?

there right hemisphere

what were the findings for the tactile tasks?

objects that were placed in the right hand could be descried in speech or writing with the right hand whereas when objects were placed in the left hand, participants could only mterm-25ake wild guesses and often seemed unaware that they were holding something

when objects were placed simultaneously in both hands and then hidden in a pile of other objects, both hands only selected their own object and ignored the other hand's object

objects that were first felt by one hand could only be recognised by that same hand- eg objects sensed by the right hand could not be recognised by the left

why were the participants hands covered for the tactile task?

this was a control to ensure that there was no visual stimuli going into either hemisphere

what were the conclusions for Sperry's experiment?

sperry concluded that people with split brains have 2 separate visual inner worlds

split brain patients have a lack of cross-integration where one hemisphere doesn't know what the other has been doing

split brain patients have 2 different independent streams of consciousness, each with its own memories