ABSTRACT
Motivation is one of the central concepts of psychology. As with most other psychological concepts we all have an intuitive grasp of what it means but find it difficult to give a precise and inclusive definition of it. When we talk about motivation we are usually concerned with the goals or purposes of somebody's actions. As psychologists we are concerned with understanding why people are pursuing particular goals at particular times and how the pursuit of those goals actually affects their behaviour. Implicit in most of our commonsense views of motivation is that it is something that arises ‘spontaneously’ within the individual, rather than being evoked by environmental circumstances. Naturally, this creates difficulties for those of us who want to study motivation within a biological framework since it is our job to specify the neural and bodily systems that generate these apparently ‘spontaneous’ events. The way we have solved this problem has been to relate motives back to needs, to argue that motivational states arise because the individual lacks something. We can then study motivational processes by controlling people's or animals’ access to things that they need and observing the impact of these variations in need state. The easiest way of controlling motivation is to work through basic biological needs, like hunger and thirst, that are common to all animals and which can be shown to have a powerful effect on behaviour. It is therefore not surprising that much of the work that has been done on motivation this century has been biologically oriented.
