Psychology, scientific study of behaviour and experience—that is, the study of how human beings and other species sense, think, learn, know, communicate and interact. Modern psychology is devoted to collecting facts about behaviour and experience and systematically organizing such facts into psychological theories. These theories aid in understanding and explaining people’s behaviour and sometimes in predicting and influencing their future actions.
Psychology, historically, has been divided into many subfields of study; these fields, however, are interrelated and frequently overlap. Physiological psychologists, for instance, study, among other things, the functioning of the brain and nervous system and the role of hormones in the endocrine system in behaviour; developmental psychologists are interested in the whole process of development, both physical and behavioural, from birth to old age. Social psychologists examine the ways in which people influence one another and the way they act in groups. Industrial psychologists study the behaviour of people at work and the effects of the work environment. Educational psychologists help students make educational and career decisions, and diagnose and treat those with learning difficulties. Clinical psychologists assist those who have problems in daily life or who are mentally ill.