Sperry’s study
The aim of this study was to test the effects of hemispheric disconnection in humans
Bilateral control means both sides of the body
Contralateral control means opposite sides of the body
Method:
This was a lab experiment with controls over specific variables
The opportunity sample consisted of 11 patients with epilepsy
They all had an operation to divide the brain in half along the corpus callosum in an
effort to control severe epileptic seizures that couldn’t be controlled by medication.
One patients had undergone the operation 5.5 years before the evaluation whilst
some only shortly before
The IV was having a split brain
The DV was the participants ability to perform different visual and tactile tests
It was a quasi experiment
Objects seen in the right visual field (RVF) are objects to the right of the fixation
point of the eye.
Objects seen in the left visual field (LVF) are objects to the left of the fixation point
of the eye.
RVF of both left and right eye go to the left hemisphere and vice versa.
Procedure:
The general procedure was to expose one or both hemispheres to a stimulus and
bring out a response
Stimulus were visual, tactual (touch) or auditory
Controls were used to reduce input from extraneous variables e.g. covering one eye.
A tachistoscope used to present information (projected for less than 1/10 of second)
Participants were to have one eye closed whilst stimuli were being presented
Everything that was projected to the left of the centre of the screen was passed via
the left visual field (LVF) and into the right hemisphere and vice versa.
Tactual information was presented below the screen where there was a gap so
participants could reach objects but not see their hands.
Objects were then placed in participant’s right or left hand or both
Information about objects placed in right hand is processed by left hemisphere and
vice versa
Results:
Quantitative data and qualitative data was gathered
The quantitative data was largely in the form of yes/no results as participants could
typically perform a task or could not.
, Qualitative data was typically descriptions of the participants’ sensations or
transcriptions of verbal responses
Visual tests:
- When participants were presented with an image in one half of their visual field
and then presented with the same image in the other half of the visual field they
responded as if they had never seen the image before since the images went to
two different hemispheres that were not connected therefore they acted as if
they hadn’t seen the image before ( as if it were aphasic – a disorder of
language/not recognising speech/unable to produce words) . 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.
- However, the participant could point with their left hand to a matching picture or
object presented among a collection of pictures and objects.
- If different figures were presented at the same time to different visual fields, for
example a $ to the LVF and a ? to the RVF, participants could draw the $ with
their left hand, but if they were asked what they had drawn, they would say the
RVF symbol (a ?). This is because only the left hemisphere can respond with
speech/writing.
Tactual test:
- Objects placed in right hand allowed participants to verbally describe or name
the object in their hand because left hemisphere is verbal.
- They could also identify the object by selecting a similar object from a series of
alternative objects
- If objects were placed in the left hand, patients could not describe what they felt
and could only make wild guesses at what the object was
- However, if the object was taken from the left hand and placed in a ‘grab bag’, or
was scrambled among other test items, the participant was able to search out
and retrieve it with their left hand.
The aim of this study was to test the effects of hemispheric disconnection in humans
Bilateral control means both sides of the body
Contralateral control means opposite sides of the body
Method:
This was a lab experiment with controls over specific variables
The opportunity sample consisted of 11 patients with epilepsy
They all had an operation to divide the brain in half along the corpus callosum in an
effort to control severe epileptic seizures that couldn’t be controlled by medication.
One patients had undergone the operation 5.5 years before the evaluation whilst
some only shortly before
The IV was having a split brain
The DV was the participants ability to perform different visual and tactile tests
It was a quasi experiment
Objects seen in the right visual field (RVF) are objects to the right of the fixation
point of the eye.
Objects seen in the left visual field (LVF) are objects to the left of the fixation point
of the eye.
RVF of both left and right eye go to the left hemisphere and vice versa.
Procedure:
The general procedure was to expose one or both hemispheres to a stimulus and
bring out a response
Stimulus were visual, tactual (touch) or auditory
Controls were used to reduce input from extraneous variables e.g. covering one eye.
A tachistoscope used to present information (projected for less than 1/10 of second)
Participants were to have one eye closed whilst stimuli were being presented
Everything that was projected to the left of the centre of the screen was passed via
the left visual field (LVF) and into the right hemisphere and vice versa.
Tactual information was presented below the screen where there was a gap so
participants could reach objects but not see their hands.
Objects were then placed in participant’s right or left hand or both
Information about objects placed in right hand is processed by left hemisphere and
vice versa
Results:
Quantitative data and qualitative data was gathered
The quantitative data was largely in the form of yes/no results as participants could
typically perform a task or could not.
, Qualitative data was typically descriptions of the participants’ sensations or
transcriptions of verbal responses
Visual tests:
- When participants were presented with an image in one half of their visual field
and then presented with the same image in the other half of the visual field they
responded as if they had never seen the image before since the images went to
two different hemispheres that were not connected therefore they acted as if
they hadn’t seen the image before ( as if it were aphasic – a disorder of
language/not recognising speech/unable to produce words) . 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.
- However, the participant could point with their left hand to a matching picture or
object presented among a collection of pictures and objects.
- If different figures were presented at the same time to different visual fields, for
example a $ to the LVF and a ? to the RVF, participants could draw the $ with
their left hand, but if they were asked what they had drawn, they would say the
RVF symbol (a ?). This is because only the left hemisphere can respond with
speech/writing.
Tactual test:
- Objects placed in right hand allowed participants to verbally describe or name
the object in their hand because left hemisphere is verbal.
- They could also identify the object by selecting a similar object from a series of
alternative objects
- If objects were placed in the left hand, patients could not describe what they felt
and could only make wild guesses at what the object was
- However, if the object was taken from the left hand and placed in a ‘grab bag’, or
was scrambled among other test items, the participant was able to search out
and retrieve it with their left hand.
