What happens to perception and awareness when the two hemispheres of the brain are surgically separated?
Classic study: Sperry (1968), Hemisphere deconnection and unity in conscious awareness. Aim, method, results and conclusions, evaluation, and links to the biological area and hemispheric lateralisation.
An OCR A-Level Psychology answer to the classic biological study, Sperry (1968) on hemisphere deconnection. Covers the aim, the quasi-experiment with split-brain patients, the tachistoscope and tactile tasks, the lateralisation findings, evaluation, and links to Casey and the biological area.
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What this dot point is asking
Sperry (1968) is the classic study in the biological area for the theme "regions of the brain", paired with Casey. You must know its aim, method, results and conclusions, evaluate it, and explain what it tells us about the biological area and the lateralisation of brain function.
The answer
Aim and method
Because the hemispheres could no longer communicate, the task isolated what each hemisphere could do alone.
Results and conclusions
Evaluation
- Control and reliability. Standardised procedures (the tachistoscope, fixed exposure, central fixation) give high internal validity and replicability.
- Theoretical value. The study gave foundational, lasting insight into hemispheric lateralisation.
- Sample. Very small and atypical (11 patients with severe epilepsy and brain abnormality), limiting generalisability to normal brains.
- Ecological validity. Artificial lab tasks are unlike everyday brain function.
- Confounds. Individual differences (extent of surgery, prior damage) are uncontrolled in a quasi-experiment.
Examples in context
Example 1. Why this study defines the biological area. The biological area explains behaviour through physical structures and processes such as the brain. Sperry shows that specific functions (language, spatial recognition) are localised in particular hemispheres, so behaviour and awareness depend directly on brain structure. This is why OCR uses it as the classic study on regions of the brain.
Example 2. The contrast with Casey. Sperry is paired with Casey et al. (2011), who used fMRI to link self-control to activity in specific brain regions. Where Sperry uses surgical disconnection and behavioural tasks to map hemispheric function, Casey uses modern brain imaging to relate a psychological trait to neural activity. Comparing them shows how methods for studying the brain advanced, the classic-contemporary comparison the exam asks for.
Try this
Q1. Name the structure that is cut in a commissurotomy. [1 mark]
- Cue. The corpus callosum (the band of fibres connecting the two hemispheres).
Q2. Explain why a stimulus in the right visual field could be named. [2 marks]
- Cue. The right visual field projects to the left hemisphere, which is specialised for language, so the patient can verbally name what was seen.
Q3. Explain one weakness of Sperry's sample. [2 marks]
- Cue. It was very small and atypical (11 patients with a history of severe epilepsy and brain abnormality), so the findings may not generalise to people with intact, typical brains.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 201910 marksDescribe the method and results of Sperry's (1968) split-brain study. [10 marks]Show worked answer →
A description item testing method and results (AO1).
Method: a quasi-experiment (and case study) on 11 patients who had undergone a commissurotomy (cutting of the corpus callosum) to treat severe epilepsy, compared with people with intact brains. Using a tachistoscope, a visual stimulus was flashed to either the left or right visual field for about a tenth of a second while the patient fixated centrally, so information reached only one hemisphere. Patients also handled hidden objects with one hand. They were asked to name or describe what they saw or felt, or to select it.
Results: when a stimulus was shown to the right visual field (processed by the language-dominant left hemisphere), patients could name it. When shown to the left visual field (right hemisphere), they could not name it (saying they saw nothing) but could select the matching object with the left hand. Objects felt by the left hand (right hemisphere) could not be named but could be recognised non-verbally. Each hemisphere thus processed information independently.
Markers reward the commissurotomy patient sample, the tachistoscope and tactile procedures with central fixation, and the key results (right visual field named, left visual field not named but selectable by the left hand).
OCR 202112 marksDiscuss the strengths and weaknesses of Sperry's (1968) study. [12 marks]Show worked answer →
A balanced evaluation (AO3) using method to support points.
Strengths: highly controlled, standardised procedures (the tachistoscope, fixed exposure time, central fixation) give strong internal validity and replicability, allowing clear inferences about hemispheric function; and the work gave major, lasting insight into lateralisation of language and visual processing.
Weaknesses: a very small, unusual sample (11 split-brain patients with a history of severe epilepsy and brain abnormality), so findings may not generalise to typical brains; the artificial laboratory tasks are unlike everyday brain function, lowering ecological validity; and individual differences between patients (extent of surgery, prior brain damage) act as confounds in a quasi-experiment with no manipulated IV.
A strong answer concludes that the controlled methods produced robust, foundational findings about lateralisation, but the small atypical sample and artificial tasks limit generalisability. Markers reward developed strengths and weaknesses with a judgement.
Related dot points
- Contemporary study: Casey et al. (2011), Behavioral and neural correlates of delay of gratification. Aim, method, results and conclusions, evaluation, and links to the biological area and Sperry.
An OCR A-Level Psychology answer to the contemporary biological study, Casey et al. (2011) on the neural correlates of delay of gratification. Covers the aim, the longitudinal follow-up of Mischel's marshmallow participants, the go/no-go task and fMRI, the prefrontal cortex and ventral striatum findings, evaluation, and links to Sperry and the biological area.
- Classic study: Blakemore and Cooper (1970), Development of the brain depends on the visual environment. Aim, method, results and conclusions, evaluation, and links to the biological area and neuroplasticity.
An OCR A-Level Psychology answer to the classic biological study, Blakemore and Cooper (1970) on how the visual environment shapes brain development. Covers the aim, the controlled-rearing animal study with vertical or horizontal stripes, the behavioural and neural findings, evaluation, ethics, and links to Maguire and the biological area.
- Contemporary study: Maguire et al. (2000), Navigation-related structural change in the hippocampi of taxi drivers. Aim, method, results and conclusions, evaluation, and links to the biological area and Blakemore and Cooper.
An OCR A-Level Psychology answer to the contemporary biological study, Maguire et al. (2000) on the hippocampi of London taxi drivers. Covers the aim, the MRI quasi-experiment with VBM and pixel counting, the posterior and anterior hippocampus findings, the correlation with experience, evaluation, and links to Blakemore and Cooper and the biological area.
- Research methods and techniques: experiments, self-report, observation and correlation; variables and operationalisation; experimental designs; hypotheses; and the strengths and weaknesses of each method.
An OCR A-Level Psychology answer to research methods and design, covering laboratory, field and quasi-experiments, self-report, observation and correlation, independent and dependent variables, operationalisation, experimental designs, directional and non-directional hypotheses, and the strengths and weaknesses of each technique for Component 1.
- Sampling methods, ethical considerations, reliability and validity, levels of measurement, and recording, analysing and presenting data.
An OCR A-Level Psychology answer to sampling and data handling, covering random, stratified, systematic, opportunity and self-selected sampling, BPS ethics, reliability and validity, levels of measurement, and how to record, analyse and present qualitative and quantitative data for Component 1.
Sources & how we know this
- OCR Level 3 Advanced GCE in Psychology (H567) specification — OCR (2015)