Evaluations - A03

• Strength of lateralisation - S&G's research innovative and ingenious method, allows psychologist scientifically study split brain patients. Scientists difficult time conceiving standardised method, thus Sperry developed original method using lab based conditions asking participants fixate on dot while image flashed 1/10 of second and flashing images either to left / right visual field. Sperry's original method allowed objective and operationalised method, can be replicated test for validity, therefore lateralisation considered highly valid.

  COUNTER - artificial task, lacks ecological validity
• Strength of lateralisation - practical applications, Sperry's conclusions about functions of left and right hemisphere applied to specifically designed rehabilitation programs that focus of verbal or visual spatial therapy (EG those with damaged left hemisphere focus on speech therapy). Understanding of lateralisation help those with brain damage perform specific tasks to accelerate rate of recovery of specific area. Therefore research useful as it contributes to helping people in real life.
• Limitation of lateralisation - lateralisation changes with age. Szaflarski found language more lateralised to left hemisphere throughout childhood and adolescence but after age of 25 lateralisation decreases with each decade of life and shows bilateral patterns. Shows our brain not work same lateralised way throughout life, fact it changes to bilateral patterns with age makes us question S&G's conclusions as if lateralisation's brains way of functioning, should be demonstrated by all individuals regardless of age. Thus problem as functions of each hemisphere not definite reducing validity.
• Limitation of lateralisation - issues of generalisability, Sperry's experiment 11 patients history of epileptic seizures, while all had corpus callosum cut, some had other connections (anterior commissure) between left and right hemisphere still intact. Problem as epilepsy affected brains in different ways and their brain activity not always generalised to people without epilepsy, inconsistency of disconnection between right / left hemisphere shows ppts had large individual differences which affected internal validity. Thus conclusions invalid, not apply to ppl with normal functioning brain.