Sperry - evaluation
Research method
Lab experiment
Two conditions (level of IV) were directly compared
Comparisons were to non-split brain people but these people were not included in the sample which would have provided a better comparison
Sampling bias
11 men and women who had undergone commissurotomies for epilepsy
11 sounds like small sample but given rarity of condition quite impressive
All participants suffer from epilepsy so generalisation to whole population may be invalid especially as epilepsy is a brain disorder and findings relate to brain function
Data
Collected qualitatove and quantitative data which was useful in interpreting the findings
Qualitative data supporting tests 6 and 7 help show understanding of the effect of hemispheric deconnection is correct
Reliability
Lab experiment so easy to replicate and it has been repliacted and the results were generally supported
Damage to the left hemisphere early on could be compensated by the RH so the epileptic sample is unrepresentative
Another study found compensation led to participants ability to respond verbally when in LVF, so Sperry's study is less generalisable
Validity
Lab experiment so highly controlled and extraneous variables could be eliminated and could be sure IV directly affecting DV - image shown for 1/10th second so eyes didn't have time to move
Low ecological validity as lab experiment so artificial environment, also task is not realistic as in real life they would use both eyes simultaneously and the left hemisphere could speak out to inform the right hemisphere
Ethnocentrism
Evidence of different lateralisation in people using different languages so other cultures could produce different results
Sperry's results only apply to cultures with same lateralisation of English speakers
Ethics
Ethical issues in surgery but none in experiment
Experiment is helping understand their mental tiredness and finding ways for them to be like normal people and help them make progess