Hemispheric Lateralisation and Split-Brain Research
Hemispheric lateralisation: refers to the fact that certain functions/mental processes in the brain
are mainly specialised to either the left or right hemisphere / Each hemisphere has functional
specialisations
E.g. the left hemisphere is dominant for language and speech and the right excels at visual motor
tasks
Split Brain Research: Research that studies the behaviour of individuals who have had the 2
hemispheres of the brain surgically separated by severing the corpus callosum.
Corpus Callosum: The two hemispheres are connected through nerve fibres called the corpus
callosum which facilitate interhemispheric communication (allowing the left and right
hemispheres to exchange information)
The Brain is Contralateral
As a general rule, the activity on the left hand side of the body is controlled by the right hemisphere
and vice versa (controls opposite sides)
Investigating Hemispheric Lateralisation
The chance to investigate the different abilities of the 2 hemispheres came about when in a
treatment for severe epilepsy, surgeons cut the bundle of nerve fibres that formed the corpus
callosum / Aim = to prevent the violent electrical activity that accompanies epileptic seizures
crossing from one hemisphere to the other. These are known as split-brain patients. Because the
corpus callosum is cut, information has no way of travelling to the other hemisphere and can be
processed only in the hemisphere that received it.
Sperry and Gazzaniga’s Split Brain Research (1967)
Aim: To test the theory of hemispheric lateralisation and investigate the extent to which the two
hemispheres of the brain function independently when the corpus callosum is severed.
Procedure:
Visual test (describe what you see)
Participants are told to look at a fixation point Participants are told to look at a fixation point
on a screen while an image is presented for on a screen while an image is presented for
one tenth of a second to the left visual field one tenth of a second to the right visual field
and processed by the right hemisphere. and processed by the left hemisphere.
Participants give a verbal response. Participants give a verbal response.
Drawing test
Image is drawn by the left hand, controlled by Image is drawn by the right hand, controlled
the right hemisphere. by the left hemisphere
, Findings:
Visual test (describe what you see)
If an image was presented to the left visual If an image was presented to the right visual
field, the patient could not verbally describe field, the patient could verbally describe what
what was shown and often reported that they saw.
nothing was present.
This is because the information is received by
This is because the right hemisphere is the left hemisphere, which is dominant for
dominant for visual motor tasks. The right language and can therefore say that it has
hemisphere can see the picture but as it has seen it.
no language centre, it cannot respond
verbally. The left hemisphere, which does have
a language centre, does not receive
information about seeing the picture, and
therefore cannot say that it has seen it.
However, if you put a pen in their left hand,
they could draw what they saw.
Drawing test
If an image was drawn by the left hand If an image was drawn by the right hand, the
(controlled by the right hemisphere), the left right hand would attempt to draw a picture,
hand would consistently draw clearer and but the picture was never as clear as the left
better pictures than the right hand (even hand.
though all participants were right-handed).
This is because the right hand is controlled by
This is because the left hand is controlled by the left hemisphere, again, demonstrating the
the right hemisphere, demonstrating the superiority of the right hemisphere when it
superiority of the right hemisphere when it comes to visual motor tasks.
comes to visual motor tasks.
Conclusion:
The findings demonstrate that the left hemisphere is responsible for speech and language, and
the right hemisphere specialises in visual-spatial/motor processing and facial recognition.
A03
Point Evidence Conclusion
There is support for Aphasia is the impaired This therefore
hemispheric lateralisation ability to understand or demonstrates the
from aphasia studies. produce speech as a result important role played by
of brain damage. Broca’s Broca’s area (located in the
aphasia is an impaired posterior portion of the left
ability to produce frontal lobe) in the
Hemispheric lateralisation: refers to the fact that certain functions/mental processes in the brain
are mainly specialised to either the left or right hemisphere / Each hemisphere has functional
specialisations
E.g. the left hemisphere is dominant for language and speech and the right excels at visual motor
tasks
Split Brain Research: Research that studies the behaviour of individuals who have had the 2
hemispheres of the brain surgically separated by severing the corpus callosum.
Corpus Callosum: The two hemispheres are connected through nerve fibres called the corpus
callosum which facilitate interhemispheric communication (allowing the left and right
hemispheres to exchange information)
The Brain is Contralateral
As a general rule, the activity on the left hand side of the body is controlled by the right hemisphere
and vice versa (controls opposite sides)
Investigating Hemispheric Lateralisation
The chance to investigate the different abilities of the 2 hemispheres came about when in a
treatment for severe epilepsy, surgeons cut the bundle of nerve fibres that formed the corpus
callosum / Aim = to prevent the violent electrical activity that accompanies epileptic seizures
crossing from one hemisphere to the other. These are known as split-brain patients. Because the
corpus callosum is cut, information has no way of travelling to the other hemisphere and can be
processed only in the hemisphere that received it.
Sperry and Gazzaniga’s Split Brain Research (1967)
Aim: To test the theory of hemispheric lateralisation and investigate the extent to which the two
hemispheres of the brain function independently when the corpus callosum is severed.
Procedure:
Visual test (describe what you see)
Participants are told to look at a fixation point Participants are told to look at a fixation point
on a screen while an image is presented for on a screen while an image is presented for
one tenth of a second to the left visual field one tenth of a second to the right visual field
and processed by the right hemisphere. and processed by the left hemisphere.
Participants give a verbal response. Participants give a verbal response.
Drawing test
Image is drawn by the left hand, controlled by Image is drawn by the right hand, controlled
the right hemisphere. by the left hemisphere
, Findings:
Visual test (describe what you see)
If an image was presented to the left visual If an image was presented to the right visual
field, the patient could not verbally describe field, the patient could verbally describe what
what was shown and often reported that they saw.
nothing was present.
This is because the information is received by
This is because the right hemisphere is the left hemisphere, which is dominant for
dominant for visual motor tasks. The right language and can therefore say that it has
hemisphere can see the picture but as it has seen it.
no language centre, it cannot respond
verbally. The left hemisphere, which does have
a language centre, does not receive
information about seeing the picture, and
therefore cannot say that it has seen it.
However, if you put a pen in their left hand,
they could draw what they saw.
Drawing test
If an image was drawn by the left hand If an image was drawn by the right hand, the
(controlled by the right hemisphere), the left right hand would attempt to draw a picture,
hand would consistently draw clearer and but the picture was never as clear as the left
better pictures than the right hand (even hand.
though all participants were right-handed).
This is because the right hand is controlled by
This is because the left hand is controlled by the left hemisphere, again, demonstrating the
the right hemisphere, demonstrating the superiority of the right hemisphere when it
superiority of the right hemisphere when it comes to visual motor tasks.
comes to visual motor tasks.
Conclusion:
The findings demonstrate that the left hemisphere is responsible for speech and language, and
the right hemisphere specialises in visual-spatial/motor processing and facial recognition.
A03
Point Evidence Conclusion
There is support for Aphasia is the impaired This therefore
hemispheric lateralisation ability to understand or demonstrates the
from aphasia studies. produce speech as a result important role played by
of brain damage. Broca’s Broca’s area (located in the
aphasia is an impaired posterior portion of the left
ability to produce frontal lobe) in the
