The brain is made up of two
hemispheres, the left and
the right. These two
hemispheres are connented
by the Corpus Collosum.
The left hemisphere
is the 'logical' side. It
(both to apprehend
and to speak) and
uses logic to reason
The right hemisphere
is the 'creative' side
which processes whole
spatial awareness and
The Corpus Collosum
is a bundle of nerves
which connects both
processed from one
side of the brain to relay
into the other side.
The aim of this study was to investigate how
the effect of hemisphere deconnection and to
show each hemisphere has different functions.
11 participants who had undergone the sugery which severs the Corpus Callosum.
Only two of these were
described in detail.
The first - A male who had had been suffering from seizures for more than 10 years, an average
of two major attacks per week before beggining to suffer reccuring seizure which were at a high
death risk. Since having the surgery, the participant has had no seizures and had significantly
reduced his medivation and reported an overall improvement in health.
The second - A female in her thirties who reported that she was also seizure free since the operation
which was four years prior. The EEG scan she had was reported to have a normal pattern.
Based on the sucess of the first two patients, the surgery
was extended to the other nine also used in this study.
The participants had had the surgery before the study, Sperry took no part in it - The independant variable had not been manipulated.
1) Sperry used a specially designed
apparatus that allows information to
reach only one hemisphere.
2) Images flashed on the screen for 1/10 of
a second so that information could not be
seen by the other hemisphere.
3) The stimulus (the images or words) would be placed either
left or right the fixation point at the centre of the screen and
participants would be asked to say or draw whet they saw.
Tactile Tasks - Objects would be placed in one of the subjects
hands (screened from view) and then, after the item had been
removed from the participants hand, were asked to take the
same item from from a bag with the same/alternative hand.
The same image was
shown to each participant.
Length of time shown was the
same for each participant.
Same experimenter used.
Possibility of different interpretations/obervations are lessoned.
Same object is placed in
each participants hand.
Type of Data
The majority of this study is quantitatve data.
-Sperry records whether something can be identified or not which allows him to make later conclusions about how the two hemospheres differ in their functions.
The qualitative data that Sperry recorded were the experiences of the 'split-brain' patients which add significantly to the attempt to understand why/how thier experiences occured.
1) Images shown in one half of their visual field
and then presented with the same image in the
other half of the visual field responded as if they
had never seen the image before.
If the same image was presented in the original
visual field the participants were able to recognise
the image as one they had seen before.
4) Right hand + Object = Speech
Left hand + Object = Inability to speak - but ability to
find the object again in the grab bag.
Right hand side could also:
Select similar items, E.g. Clock - Watches.
Can perform simple arithmetic operations.
Arithmetic operation - A mathematic operation involving numbers.
Can understand both written and
spoken word, but cannot be understood.
Can identify objection but cannot be verbally speak them.
Can understand instructions
3) 2 Symbols shown simultaneously (e.g. a dollar sign (LVF) and a question
mark (RVF)), draw the left (dollar sign) and say the right (question mark).
RVF - Right visual field
LVF - Left Visual field
2) Left visual field - Participants could not talk of the
image if shown on the left hand side of the visual field.
They could respond non-verbally by pointing
with their left hand to the matching picture of
selecting an object presented among a
collection of other pictures and objects.
This only works
Over the extranuous variables.
No ethical issues were breached during this study.
Of the small amount of people who have had the operation.
Allowed the researchers to investigate the variables in strict laboratory conditions. (The functioning of the two brain hemispheres have never been studied in such depth before)
Can be replicated with new split-brain patients.
Ability to be
The small sample of 11 means it cannot be generalised to the whole public - seeing as spilt-brain patients are not a common thing - it is not suprising.
The fact it was a quasi-experiment meant that the experimenter had no control over the independant varibles.
The procedure Sperry uses, seperating the two visual fields is something unlikely to occur in real life and if it did - The split brain patients have methods which allow them to cope with such events.
However, ecologically valid research is studying real problems, which is something Sperry does - Looking at the naturally occurring variable of the results of the split-brain surgery is studying the real life problem. Attempting to understand the effects of the proceedure and if the operation should be any cause for concern for the individuals undergoing it.
May not be able to compare 'split brain' (severe epilectic brain) to a normal brain.
This study had been deemed very useful as it revealed facts
about the lateralisation of the functions between the two
hemispheres that had only been suggested by previous studies.
Both hemisphere's have
their own functions
The left is responsible for language
and the right side of the body.
The right side is responsible for spatial
awareness and the left side of the body.