Core studies: Sperry (1968) on split-brain patients and Damasio et al. (1994) on the case of Phineas Gage, including their aims, methods, results, conclusions and evaluation.

What this dot point is asking

Edexcel names two core studies for Topic 4: Sperry (1968) on split-brain patients, which revealed lateralisation, and Damasio et al. (1994), who reconstructed the skull of Phineas Gage to study how frontal-lobe damage affects behaviour. Know each study's aim, method, results and conclusion, and evaluate the use of such case studies.

Sperry (1968): split-brain patients

The aim was to investigate the abilities of each hemisphere separately in patients whose hemispheres could no longer communicate.

The method used split-brain patients, people whose corpus callosum had been surgically cut to treat severe epilepsy, so the left and right hemispheres could not pass information to each other. Using a tachistoscope, Sperry flashed an image or word to one visual field only, so the information reached only one hemisphere. Patients were asked to say what they saw or to select an object by touch with one hand behind a screen, testing what each hemisphere could do alone.

The results showed clear differences. When an object was shown to the right visual field (processed by the left hemisphere), the patient could name it, because the left hemisphere controls language. When shown to the left visual field (processed by the right hemisphere), the patient could not say what it was, but could select it by touch with the left hand. The conclusion was that the two hemispheres are specialised (lateralised): the left for language, the right for non-verbal and spatial tasks, and they normally share information through the corpus callosum.

Damasio et al. (1994): the case of Phineas Gage

The aim was to investigate which brain areas were damaged in the famous case of Phineas Gage and how this related to his change in behaviour. Gage was a railway worker who, in 1848, survived an iron bar passing through his skull, after which his personality reportedly changed (he became more impulsive and unreliable).

The method used Gage's preserved skull and modern neuroimaging and measurement to reconstruct the likely path of the iron bar through his brain. The results suggested the bar damaged parts of the frontal lobe involved in rational decision making, planning and the processing of emotion, rather than areas controlling movement or language. The conclusion was that the frontal lobe plays a key role in personality, emotion and decision making, fitting Gage's reported change while his movement and speech were spared.

Evaluating case studies of the brain

A balanced view is that case studies are invaluable where experiments are impossible, but their findings should be supported by other methods, such as scanning healthy brains.

Try this

Q1. What had been cut in Sperry's split-brain patients? [1 mark]

• Cue. The corpus callosum (the band linking the two hemispheres).

Q2. Which brain area did Damasio link to Gage's personality change? [1 mark]

• Cue. The frontal lobe (areas involved in decision making and emotion).

Q3. Explain one weakness of using case studies to understand the brain. [2 marks]

• Cue. They use small, unusual samples, so the findings may not generalise to everyone.