At the same time they interact with social factors. This is further affected by the hormone system. This is partly because of physiological factors, but their behaviour is the outcome of these interacting with environmental factors such as family, education, social conformity and conditioning, and opportunities. This term is now generally used to cover a number of topics, including perception, learning, memory, thinking and reasoning, and language, all of which are closely related, as well as indicating a general approach to psychological problems. Some of the early studies concentrated on rote learning of nonsense syllables, and on classical conditioning, the way in which a neutral stimulus can become a trigger for a natural response, as when the sight or thought of food makes a person salivate.
Operant conditioning refers to learning when an action is rewarded or reinforced.
A great deal of human behaviour is more complex than this, and the stress now is largely on meaning and organization. This branch of psychology is based on the notion that the origins of behaviour lie in the combination of genes which is present at the moment of conception, and that it continues to develop throughout life, as the inherited potential is modified by both physical and social factors. The Swiss psychologist Jean Piaget led the way in showing the complexity of intellectual development as children develop the capacity for independent rational thought. Children that are gifted, average, or have disabilities all need a stimulating and supportive environment to make the most of their potential, while in old age abilities both physical and mental can be maintained by active use. Developmental psychologists explore these processes in detail.