Evaluations - A03

• Strength of localisation - supporting evidence for role of language centres, evidence for different functions of Broca's and Wernicke's areas in language production and understanding comes from discovery that damage to these different areas result in different types of aphasia (impaired language ability), for example damage to Broca's area results in difficulty with speech production. Confirms understanding of localisation, shows that different brain regions have specific functions damage causes deprivation. Thus increasing validity.

  COUNTER - solidified by case of Phineas Gage study
• Strength of localisation - further support as there has been advances in brain scanning techniques. Peterson et al used brain scans to demonstrate that Wernicke's area active during listening task and Broca's area active during reading task. As different areas active while brain undertakes different set of functions, demonstrates functionality compartmentalise to specific regions. Therefore increases validity of theory.

  COUNTER - However this is correlational research as there is not direct cause-effect; also artificial material as everyday tasks more complex, lacks ecological validity.
• Limitation of localisation - research found individual differences in functioning of language areas. Bavelier et al found large differences between individuals in patterns of brain activity in language areas during silent reading tasks, observed activity on right temporal lobe as well as left frontal, temporal and occipital lobe. Shows functioning of complex behaviours arise from different areas in different people or we would've observed same activation patterns in everyone performing same task. Therefore localisation of function overly simplistic for complex behaviours, reducing validity.
• Limitation of localisation - contradicted by valid research from plasticity and functional recovery. Lashley's law of equipotentiality state when brain damaged surviving regions 'chip in'. Documented cases of stroke patients who rewired brain to recover abilities which were lost during illness. Thus plasticity research shows when brain damaged and particular function lost then rest of brain able to reorganise in attempt to recover lost function. Therefore ability to take on other functions refutes notion one part of brain only execute one function. Localisation theory incomplete.