Hemispheric Lateralisation

• lateralised brain functions

  • Sperry & Gazzaniga – LHem is more analytical and for verbal tasks, RHem for spatial tasks & music
  • RHem only produce rudimentary words and phrases but adds emotional and holistic content to language
  • LHem is analyser, RHem is synthesiser
• AO3 strength - Methodology 



  • Sperry 1968 – presented visual stimulus one hemispheric field and visual field at a time, flashed up for 1/10th of a second
  • minimal time for info to spread to other hemisphere and eventually both sides of brain
  • specialised and standardised procedure–ruled out EV and CVs so increases internal validity
• AO3 limitation - uncontrolled sample



  • epileptic patients take anti-epilepsy medicine for different periods; degree of lesioning in commissurotomy ranges in patients
  • affected ability to recognise objects and match words – cerebral neuronal changes
  • affected extent to which hemispheres communicate
  • issues with generalisability – CVs not controlled, unreliable casual conclusions
• language is lateralised...

  by the left hemisphere
• motor area is contralateral wiring 


  the RH controls movement on the left side of the body whilst the LH controls movement on the right
• vision is contralateral and ipsilateral


  each eye receives light from both the left and right visual fields. the LVF is connected to the RHem and the RVF is connected to the LVF - this aids depth perception and enables comparison of perspective
• ipsilateral

  same-side
• contralateral

  opposite
• Sperry's sample

  11 epileptic patients with a split-brain, severed corpus callosum from commissurotomy
• how does a split-brain patient differ from a 'normal' brain?

  in a 'normal' brain, the corpus callosum would immediately communicate the info to both hemispheres, giving a complete picture. However, info cannot be conveyed from one hemisphere to the other for a split-brain patient.
• commissurotomy

  severing the corpus callosum that connects the 2 hemispheres
• AO3 limitation - not as adaptive as plasticity

  • Rogers 2004 = lateralised chickens can find food and be vigilant for predators, 'normal' chickens couldn't - lateralisation enables two tasks to be done simultaneously and efficiently
  • However, neural plasticity is more adaptive because it is based on the compensation of functions when a change occurs, specifically trauma/damage - Holland 1996 = language can switch sides
• AO3 limitation - over exaggerates differences in function

  • Pucetti (1980) = cases of left-handed split-brain patients but still produce and comprehend speech in the RHem
  • lateralisation claims drastic distinctions - LHem is for language (analyser) whilst the RHem is for visual- spatial tasks (synthesiser)
  • this has given a false impression that the two hemispheres are ‘opposite’ in function and that they can receive such labels. Yet, Pucetti's findings oppose this. Therefore, it is important not to jump to conclusions and to consider that each hemisphere is not restricted to specific functions.