outline and evaluate split brain research Flashcards
outline
In a laboratory experiment using a repeated measures design, Sperry asked 11 split brain participants to face a screen, focusing on a central fixation point.
- presented with words or images (for 1/10th of a second) in their left or right visual field, before reporting what they had seen.
- Due to the short presentation time and their divided visual field, Sperry could be confident that information presented in the right visual field was processed in the left hemisphere, without being shared with the other hemisphere, and vice versa.
- From this research, he was able to establish the hemispheric lateralisation of particular functions.
In the first variation, participants were presented with words in their left visual field and were asked to identify (by touch) the correct item using their left hand.
- Participants were able to identify by touch the correct item, however, they could not report having seen the word and were unable to explain why they had selected the object.
In the second variation, participants were presented with words in their left visual field and were asked to write the word using their left hand.
- Participants were able to correctly write the word they had been shown, despite not being able to verbally report having seen a word.
In the third variation, participants were presented with images of shape in their left or right visual field, before being asked to draw it.
- Participants were able to accurately draw images presented in their left visual field but unable to draw images presented in the right visual field.
In the 4th variation, participants were presented with images of faces in their left or right visual fields, before being asked to identify the face.
- They were able to identify the correct face when it was presented in the left visual field but were unable to identify it when presented in the right visual field.
limit 1
A limitation of Sperry’s split-brain research is that it has high individual differences, because variations between the split-brain participants were not properly controlled.
This is because the disconnection between hemispheres was greater in some patients than in others before their commissurotomy.
These differences may have undermined the internal validity of research into hemispheric lateralisation.
limit 2
A further limitation is that it has low external validity. Which is when it is difficult to generalise the findings to wider populations.
This is because Sperry’s research only used 11 patients with brain damage.
Therefore, it is hard to make generalisations to neurotypical participants, who make up most of the wider population.
However, in defence of Sperry’s research, it would have been impossible to overcome this issue as so few commissurotomy patients exist.
limit 3
A final limitation of Sperry’s research is that it has extraneous variables, which is when a study has not controlled for all variables that could affect the DV, decreasing the internal validity of research.
This is because some patients had experienced drug therapies to reduce their epileptic symptoms for much longer than other patients.
Therefore, we cannot be certain that it was the commissurotomy that was causing the results in Sperry’s research.
