Introduction Psychobiology is a subdiscipline of psychology that seeks to explain behaviour in terms of biological mechanisms. Psychobiology is also known as biopsychology, biological psychology and behavioural neuroscience. Many general textbooks have a section on (or even called) the ‘biological bases of behaviour’. This title is somewhat misleading. It implies that the biological influences on behaviour are a one-way street: that biology affects behaviour. In fact, an organism’s behaviour and its environment can in turn influence its biology. The use of the term ‘environment’ here refers to everything outside the organism. As we will see, the process of evolution demonstrates an environmental influence over a long period of time. In this section on psychobiology we will examine how both biology and the environment interact to produce and influence behaviour.