Biology is defined as the study of life (from the Greek bios meaning ‘life’ and logos meaning ‘study’). A biological perspective is relevant to the study of Psychology in three ways:

1. Comparative method: different species of animal can be studied and compared. This can help in the search to understand human behaviour.

2. Physiology: how the nervous system and hormones work, how the brain functions, how changes in structure and/or function can affect behaviour. For example, we could ask how prescribed drugs to treat depression affect behaviour through their interaction with the nervous system.

3. Investigation of inheritance: what an animal inherits from its parents, mechanisms of inheritance (genetics). For example, we might want to know whether high intelligence is inherited from one generation to the next.

Each of these biological aspects, the comparative, the physiological and the genetic, can help explain human behaviour.

The biological approach believes that most behaviour is inherited and has an adaptive (or evolutionary) function. For example, in the weeks immediately after the birth of a child, levels of testosterone in fathers drop by more than 30 per cent. This has an evolutionary function. Testosterone-deprived men are less likely to wander off in search of new mates to inseminate. They are also less aggressive, which is useful when there is a baby around.
Biological psychologists explain behaviours in neurological terms, i.e. the physiology and structure of the brain and how this influences behaviour. Many biological psychologists have concentrated on abnormal behaviour and have tried to explain it. For example biological psychologists believe that schizophrenia is affected by levels of dopamine (a neurotransmitter). These findings have helped psychiatry take off and help relieve he symptoms of the mental illness through drugs. However