Hemispheric lateralisation

• What is hemispheric lateralisation?

  • The difference between functioning between the two halves of the brain
  • Specific processes carried out entirely/mainly by one hemisphere
  • A particular hemisphere largely in control of a function = dominant hemisphere
• Which side of the body is controlled by which side of the brain?

  • Left body = right hemisphere
  • Right body = left hemisphere
  • Brain = contra-lateral -> most functions split between two halves of brain
• How does the brain show lateralisation?

  • Each half mostly receives info from the senses to + has motor functions controlled by opposite side of body
  • Left hemisphere lateralisation
  • Right hemisphere lateralisation
• Left hemisphere lateralisation:

  • Verbal + analytical -> works best when stimuli must be broken down into basic parts to be understood then utilised
  • Seen in its language processing functions -> Broca's + Wernicke's areas are in left hemisphere
• Right hemisphere lateralisation:

  • Visuospatial + holistic -> works best with stimuli as a whole rather than parts
  • Enables understanding + use of spatial relationships between objects
  • Clarke, Assal + de Tribolet (1993) -> right hemisphere involved in spatial mapping
  • Emotional -> more able to recognise others' emotions in right hemisphere
  • Heller + Levy (1981)
• Sperry + Gazzaniga's research -> hemispheric lateralisation in 'split-brain' patients (p1)

  • Method: quasi experiment, independent groups design
  • IV: whether patients had commissurotomy or not (corpus callosum severed to treat severe epilepsy)
  • DV: performance on visual + tactile tasks
  • Sample: 11 people who had commissurotomies for epilsepy
  • Control group: 11 people without commissurotomies (no need -> no epilepsy)
• Sperry + Gazzaniga's research -> hemispheric lateralisation in 'split-brain' patients (p2)

  • Procedure:
  • Lab experiment using 'divided field' technique
  • Ppts asked to focus on dot in the middle of a split screen projected straight ahead of them
  • Images/words flashed on either side for 0.2 seconds
  • Ppts asked to either verbally report what they saw, draw it or identify it by touch -> all conditions tried with both hands across various trials