In Sperry’s (1968) split-brain study, a major methodological concern that threatens the internal validity of the findings when comparing the experimental group to a comparison group of 'normal' individuals is that
the comparison group of 'normal' individuals lacked a history of severe epilepsy and anti-convulsant medication, introducing a major confounding variable.
the control group was tested using a naturalistic field experiment design, meaning their cognitive responses lacked standardised laboratory controls.
the experimental group had their optic chiasm surgically severed in addition to the corpus callosum, which was not matched in the control group.
the control group had undergone a partial commissurotomy, which allowed partial interhemispheric transfer and prevented a true baseline comparison.
