Localisation of function evaluation

RTS: Phineas Gage suffered an accident when a large metal pole was forced up through his head following an industrial accident, removing most of his left frontal lobe. Amazingly, he survived, his personality changed from being charming & polite to being short-tempered & rude. This supports localisation of function because it suggests that the frontal lobe may be responsible for personality & since it got damaged only his personality was affected. If localisation of function was more holistic then it would suggest that he would suffer from more effects (i.e damage to sight, speech etc) 

Generalisability: problems generalising the findings to a wider population - only focus on one person (i.e Phineas Gage) the personality change may have been due to the experience itself - which may have been traumatic. Low population validity. 

Evidence from brain scans: Petersen et al found that Wernicke’s area was active when performing listening tasks, and Broca’s area was active when undertaking reading tasks. This supports the idea that different areas of the brain have specific functions. 

Counterpoint: Lashley's work suggests that higher cognitive functions (stages involved in learning) are localised but are distributed in a more holistic way in the brain. He removed areas of the cortex in rats that were learning in a maze and found that no area was proven to be more important than any other area in terms of learning. The learning process appeared to require every part of the rat's cortex. This suggests that learning is too complex to be localised & requires the whole brain to be involved.