Major thinkers associated with: William James

It functioned on the mind's functions and adaptations. Instead of focusing on the mental processes themselves, functionalist thinkers were interested in the role that these processes play.

Gaining a better understanding of the purpose would allow psychologists to better understand how the mind allows people to respond and adapt to their environments.

Major thinkers associated with: Max Wertheimer, Wolfgang Köhler, and Kurt Koffka

Instead of breaking down thoughts and behavior to their smallest elements, the gestalt psychologists believed that you must look at the whole of experience. According to Gestalt thinkers, the whole is greater than the sum of its parts, a philosophy known as holism

Major thinkers associated with: John B. Watson, Ivan Pavlov, and B. F. Skinner

Behaviorism suggests that all behavior can be explained by environmental causes rather than by internal forces. Behaviorism is focused on observable behavior.

(This school have significally impact the course of psychology. Many ideas and techniques that emerged from this school of thought are still widely used today)

Major thinkers associated with: Sigmund Freud,  Anna Freud and Otto Rank, and neo-Freudians such as Erik Erikson, Alfred Adler, and Karen Horney

The human mind was composed of three elements, which their interaction led to all of the complex human behaviors:

• the id (primal urges),
• ego (personality charged with dealing with reality),
• superego (Holds all the ideals and values from our parents and culture)

Other important theories included the idea of the conscious and unconscious, Freud's psychosexual approach to personality development, and the concept of life and death instincts.

Major thinkers associated with: Abraham Maslow, Carl Rogers, and Clark Moustakas

Humanistic psychology focus on helping people achieve and fulfill their potential. Humanistic psychology focused on topics such as: Becoming a fully functioning person, Individual free will, Hierarchy of needs, Peak experiences, and Self-actualization

Major thinkers associated with: Jean Piaget, Lev Vygotsky

Cognitive psychology is the school of psychology that studies mental processes, including how people think, perceive, remember and learn. This branch of psychology is related to other disciplines such as neuroscience, philosophy, and linguistics.