Core study 17- Sperry (B) Flashcards
The Split-brain study
What does lateralisation mean?
The theory that behavioural functions are controlled by specific regions of the brain
Background
What is brain lateralisation?
The fact that our brains are split into two cerebral hemispheres:
* Right hemisphere- controls left side of body
* Left hemisphere- controls right side of our body
Which hemisphere is language believed to be lateralised to?
The left hemisphere
Language is Lateralised to the Left
Background
How did Paul Broca discover that the left frontal lobe is critical to successful speech production?
He carried out post-mortems on those that had severe speech production issues
He obsereved they had damage to the left frontal lobe
Background
What does commissurotomy mean?
The procedure to split the corpus collosum
Background
What is the corpus collosum?
The bridge which connects the two hemispheres together
Background
Is vision lateralised or non-lateralised?
Non-lateralised- it involves both hemispheres
Background
Where is information processed when shown to the Left visual field (LVF)?
Processed by the right hemisphere (RH)
Same vice versa: LVF~RH, RVF~LH
Background
Where does information process when shown to the left visual field (LVF) in terms of hemisphere and hands?
Diagram in booklet and on mindmap
LVF~RHem~LHand
Background
Where does information process when shown to the right visual field (LVF) in terms of hemisphere and hands?
RVF~LHem~RHand
Aim
What did Sperry aim to investigate?
What did he want to see specifically?
To test hemisphere de-connection in humans
- If memory and perception differ between hemispheres
- Extent to which hemispheres would usually interact to achieve memory and perception successfully
Method
What type of experiment was used and why?
Quasi experiment- participants already had a split brain or not
Method
How did the study adopt laboratory elements?
It took place in laboratory conditions and had controls
Method
What design was used?
Repeated measures
Method
What was the IV?
Whether you had a split-brain vs whether you didn’t
Method
What was the DV?
The ability to perform a variety of visual and tactile (physical) tests
Sample
What did Sperry’s sample consist of?
How many, gender, age..?
Why was there no control group used?
11 epileptic patients who had undergone a commissurotomy
Mix of ages and genders
Previous research already informed how lateralisation works in average brains
Procedure
What two things were used in both the visual and tactile tasks?
Both begin with a ‘T’
- Translucent screen- light can pass through but it isn’t clear
- Tachistoscope- projector
Procedure
What were participants instructed to do firstly on the visual task?
Cover up one eye, then centre gaze on fixed point in middle of translucent screen
Procedure
How were the visual stimuli arranged and how were these shown to participants?
- On 35mm transparencies in a standard projector
- Back projected at 1/10th of a second (too fast for eye movement to process info in wrong visual field)
Procedure
How could the tactile task be carried out in terms of it’s setup?
There was a gap below the translucent screen- touch and feel objects, but not see
Procedure
Where were the objects placed?
In either the participants’ right, left hand or both hands
Results
When would information be recognised again (visual task)?
If information was shown to the same visual field as the first time
Results
What was found about the info presented to the right visual field?
It could be described in speech and writing
Results
What was found about the same info being presented to the left visual field?
NOTE: This info goes to the right hemisphere
Participant either did not see anything/ there was only a flash of light on the left side (couldn’t be described)
Results
What was found about objects placed in the right hand?
These could be described in speech or writing
Results
When would participants have to make wild guesses about what had been placed in their hands?
If the same object had been placed in their left hand- this goes to right hemisphere- so they were unaware they were holding anything
Conclusions
Can it be confirmed that language is lateralised in the left hemisphere?
Yes
Conclusion
What did Sperry conclude split-brain patients lacked?
Cross-integration (2nd hemisphere doesn’t know what 1st hemisphere has been doing)
Conclusion
What did Sperry conclude about split-brain patients’ streams of consciousness?
They have 2 independent streams of consciousness- each with it’s own memories, perceptions and impulses
GREEDUM
How can reliability be argued as a strength?
Participants had same information and objects presented to them in visual and tactile tasks
GREEDUM
How can ethics be argued as a strength?
All 11 epileptic participants gave consent to take part in lab exp
GREEDUM
How can generalisability be argued as a weakness?
11 epileptic patients- uncommon sample
GREEDUM
How can data be argued as a weakness?
Qualitative data- info presented to LVF goes to right hemisphere- can’t be spoken
