A03

• Point: A strength of lateralisation theory is research showing that information is processed differently even in connected brains.

  Evidence: Fink (1996) used PET scans while participants were asked to focus on global elements of an image or attend to the finer details.

  Explain: The findings showed that for global elements, the RH was more active whereas for finer details, the LH tended to dominate.

  Link: Therefore, this seems to suggest that in connected brains some aspects of visual processing show hemispheric lateralisation.
• Point: A limitation is that lateralisation may not be as adaptive from an evolutionary perspective

  Evidence: For instance, it would not benefit an individual (in terms of survival and reproduction) for their brains to be too fixed in structure in case of injury.

  Explain: Evidence has shown how non-specialised areas in opposite hemispheres can take over functions, following damage caused by illness or trauma.

  Link: Therefore, this seems to suggest that lateralized functions are more flexible rather than fixed and ultimately brain plasticity is more important as it can deal with brain damage.
• Point: A strength of Sperry’s research is further supporting evidence from split-brain research.

  Evidence: For example, Gazzaniga (1989) showed split-brain participants performing better than connected controls in certain tasks, such as identifying the odd one out.

  Explain: This is because the better cognitive strategies in the LH were processing information in isolation without the interference of the inferior RH.

  Link: Therefore, this supports Sperry’s findings in that the left and right brain are distinct.
• However, a limitation of Sperry’s research is that it is hard to establish causal relationships.

  For example, the control group he used can be described as neurotypical, meaning none of those participants had epilepsy.

  This is a problem because this becomes a confounding variable because any differences Sperry found between the split-brain participants and the control group may be a result of the epilepsy.

  Therefore, it is hard to determine whether the unique features of the participants' cognitive processing abilities were actually due to hemispheric lateralisation or not.