H567/02 Section B - Biological psychology

Biological processes and behaviour

Biological psychology investigates how bodily processes contribute to behaviour and psychological functioning.

The nervous system, brain organisation, hormones and inherited characteristics can all be investigated biologically. The central question is how a biological feature relates to a psychological outcome, not merely whether a study uses a machine. A brain scan is a measurement method; it needs an explanatory hypothesis and a valid behavioural measure.

Lateralisation concerns differences in the contributions of the two cerebral hemispheres. This is more specific than saying functions are localised somewhere in the brain. The hemispheres normally communicate, including through the corpus callosum, so specialised contributions do not imply two completely independent everyday brains.

Plasticity means that the nervous system can change in response to experience or altered demands. A biological explanation is therefore not necessarily an explanation of fixed, inherited behaviour. Learning may have a biological expression, and environmental influences may change brain organisation. Nature and nurture can operate together.

Biological determinism emphasises causes in bodily processes. Identifying a neural contribution, however, does not establish that biology is the only cause or that a person cannot change. Evidence of association, causal influence and inevitability are different claims. Ask which is supported by the actual method.

Specialisation and plasticity in research

Brain research can test specialised functioning while also revealing the importance of experience.

Sperry (1968) investigated people whose hemispheric connections had been surgically severed to treat severe epilepsy. Brief visual presentations restricted information to one visual field while participants maintained central fixation. Information presented to the left visual field reached the right hemisphere. In typical tested patients it could not be named aloud, but the person could select a matching object with the left hand. Information to the right visual field, reaching the left hemisphere, could be reported verbally. The difference supports specialised hemispheric contributions and the importance of communication between hemispheres.

The surgery was not randomly assigned for research. These patients had an unusual clinical history, and their performance under restricted laboratory presentation cannot be treated as the behaviour of all people with intact brains. The test also concerns visual fields, not a simple rule that one eye sends all its information to one hemisphere.

Maguire et al. (2000) used structural MRI to compare London taxi drivers with controls. Drivers had relatively larger posterior hippocampal regions, and time as a taxi driver was positively associated with right posterior hippocampal volume. These findings are consistent with plasticity associated with intensive navigation. They do not show that the whole brain or total hippocampus was simply larger, nor does a cross-sectional association prove that driving caused every difference. Pre-existing differences could influence entry into the occupation.

Blakemore and Cooper (1970) manipulated kittens' early visual experience using an environment dominated by one line orientation and examined subsequent visual behaviour and neural responses. This provides a more direct experimental example of experience affecting the developing visual system. It also requires caution when extending animal evidence to humans and raises substantial ethical concerns about restricted development. Across the studies, biology includes both specialised organisation and responsiveness to the environment.

The power and limits of biological evidence

Biological measurements can constrain an explanation without making it complete.

A strength is convergence between different kinds of evidence. Sperry linked controlled performance differences to hemispheric disconnection; Maguire related structural measurements to navigational experience. Connecting bodily evidence with behaviour goes beyond simply asserting that a mental function must have a brain basis. Standardised tasks and scan analysis can also support systematic replication and checking.

Nevertheless, a precise scan is not automatically a causal explanation. Maguire did not randomly assign people to years of taxi driving. A third factor, such as prior navigational ability or self-selection, could contribute to both occupation and brain differences. Following people before and during training would better test change, although it would still require suitable comparison participants and control of other experiences. This applies the causal-inference principles of Component 01 to a Component 02 biological claim.

Another weakness is limited generalisability from unusual samples or other species. Split-brain patients provide an informative opportunity to study disconnection, but their surgery and epilepsy distinguish them from most people. Kittens allow controlled manipulation of development, yet species differences limit conclusions about human abilities. These limits do not make the evidence worthless; they specify the population and question it addresses.