Every academic discipline, from literature and history to sociology and theology, has competing theories or schools of thought: perspectives from which to study the subject. Psychology, the study of the mind, has hundreds of theories and subtheories, but it is possible to identify six main schools of thought every psychology student should know.
Functionalism has the most influence of any theory in contemporary psychology. Psychological functionalism attempts to describe thoughts and what they do without asking how they do it. For functionalists, the mind resembles a computer, and to understand its processes, you need to look at the software - what it does - without having to understand the hardware - the why and how underlying it.
According to Gestalt psychologists, the human mind works by interpreting data through various laws, rules or organizing principles, turning partial information into a whole. For example, your mind might interpret a series of lines as a square, even though it has no complete lines; your mind fills in the gaps. Gestalt psychotherapists apply this logic to problem-solving to help patients.
Psychoanalytic theory, which originated with Sigmund Freud, explains human behavior by looking at the subconscious mind. Freud suggested that the instinct to pursue pleasure, which he described as sexual in nature, lies at the root of human development. To Freud, even the development of children hinged on key stages in discovering this pleasure, through acts such as feeding at the mother's breast and defecating, and he treated abnormal behavior in adults by addressing these stages.
In the 1950s, B.F. Skinner carried out experiments with animals, such as rats and pigeons, demonstrating that they repeated certain behaviors if they associated them with rewards in the form of food. Behaviorists believe that observing behavior, rather than attempting to analyze the inner workings of the mind itself, provides the key to psychology. This makes psychology open to experimental methods with results that can be replicated in the same way as any scientific experiment.
Humanist psychologists teach that to understand psychology, we must look at individuals and their motivations. Abraham Maslow's "hierarchy of needs" exemplifies this approach: a system of needs, such as food, love and self-esteem, determines a person's behavior to various extents. Meeting these needs leads to a sense of self-satisfaction and solves psychological problems.
Cognitive psychology follows behaviorism by understanding the mind through scientific experimentation, but it differs from it by accepting that psychologists can study and understand the internal workings of the mind and mental processes. It rejects psychoanalysis, as it regards psychoanalytic theories about the subconscious mind as subjective and not open to scientific analysis.