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