The breadth and diversity of psychology can be seen by looking as some of its best known thinkers. While each theorist may have been part of an overriding school of thought, each brought a unique and individual voice and perspective to the field of psychology.

Much of what we know about human thought and behavior has emerged thanks to various psychology theories. For example, behavioral theories demonstrated how conditioning can be used to learn new information and behaviors. Psychology students typically spend a great deal of time studying these different theories. Some theories have fallen out of favor, while others remain widely accepted, but all have contributed tremendously to our understanding of human thought and behavior. By learning more about these theories, you can gain a deeper and richer understanding of psychology's past, present and future.

Theories of development provide a framework for thinking about human growth, development, and learning. But why do we study development? What can we learn from psychological theories of development? If you have ever wondered about what motivates human thought and behavior, understanding these theories can provide useful insight into individuals and society.

Behaviourism, a highly influential academic school of psychology that dominated psychological theory between the two world wars. Classical behaviourism, prevalent in the first third of the 20th century, was concerned exclusively with measurable and observable data and excluded ideas, emotions, and the consideration of inner mental experience and activity in general. In behaviourism, the organism is seen as “responding” to conditions (stimuli) set by the outer environment and by inner biological processes.

Multiple intelligences, theory of human intelligence first proposed by the psychologist Howard Gardner in his book Frames of Mind (1983). At its core, it is the proposition that individuals have the potential to develop a combination of eight separate intelligences, or spheres of intelligence; that proposition is grounded on Gardner’s assertion that an individual’s cognitive capacity cannot be represented adequately in a single measurement, such as an IQ score.

Conditioning is a form of learning in which either (1) a given stimulus (or signal) becomes increasingly effective in evoking a response or (2) a response occurs with increasing regularity in a well-specified and stable environment.

Social learning, in psychological theory, learning behaviour that is controlled by environmental influences rather than by innate or internal forces. The leading exponent of the concept of social learning, often called modeling, is the American psychologist Albert Bandura, who has undertaken innumerable studies showing that when children watch others they learn many forms of behaviour, such as sharing, aggression, cooperation, social interaction, and delay of gratification.

Cognitive motivational approaches have also explored the idea that human motivation is heavily influenced by a need for competence or control. Although there are several varieties of these theories, most have in common the idea that human behaviour is at least partially motivated by a need to become as much as one can possibly become. One example of this approach is the self-actualization theory of Abraham Maslow.