Humanistic psychology follows a conscious experience and focuses the individual potential of each person. It strongly focuses on free will, does not rely on experimentation and emphasizes psychological growth.

The three forces of psychology are behaviorism, humanism, and psychoanalysis which are the schools of thought that are still in use today. Functionalism and structuralism are not widely used today and physiology is a separate field from psychology. Behaviorism focuses on individual behaviors, humanism emphasizes the importance of the human experience, and psychoanalysis is a set of theories developed largely by Sigmund Freud that is stemmed from clinical research. 

Both functionalism and structuralism focused on conscious experience while psychoanalysis focused on the unconscious. It did not focus on introspection, used scientific principles and Freud, the founder of psychoanalysis, was not African American.

The functionalism school of thought is influenced by natural selection which was described by Charles Darwin in his work "On the Origin of Species." Williams incorporated aspects of survival in his idea of biological and intellectual fitness. The other scientists did not directly influence the theories of William James.

Structuralism was founded in 1892. Functionalism was founded in the nineteenth century. Humanistic psychology came about in the mid twentieth century. Transcendentalism was introduced by Ralph Waldo Emerson in the 1830's, but it is not a major psychological school of thought, rather, it is a philosophical movement.

During each of these stages, lasting from months to years, Freud theorized the id sought pleasure from a distinct set of bodily sensations and accompanying psychosexual schemas.

In psychoanalytic theory, the superego is the seat of objective internalized ideals and judgments, which provides a reference for comparison to actualized words and deeds in the exterior conscious self. People who follow the superego too closely may develop fixations or neuroses when the world (and they themselves) fail to live up to their extreme expectations.

Displacement occurs when an individual redirects socially or personally unacceptable behaviors and thoughts by shifting those behaviors and thoughts onto a more acceptable target. The redirection of energy may be to a less threatening target or merely to a more socially acceptable one.

The evolutionary perspective of psychology, largely adapted from Darwin's theories of evolution and survival of the fittest, represent psychological actions in terms of group and individual behaviors which best promote survival as a primary goal, instead of happiness, understanding or other common psychological goals. Most modern theories of behaviorism, psychobiology and cognitive behaviorism include some elements of evolutionary psychology.

Wilhelm Wundt, regarded historically as one of the founders of modern psychology, introduced his structuralist perspective in the late 1870's, as the first major psychological perspective. In direct response to this, the school of functionalism in the later 1880s was introduced by William James.

Gestalt psychology was first introduced in 1890 by Christian von Ehrenfels, though the idea of gestalt can be traced back as far as David Hume and Immanuel Kant.

Evolutionary psychology did not begin to differentiate itself from mere evolutionary biology until well into the 20th century, with most historians placing the actual date around the 1960's-1980's (Donald Symons likely being the first dedicated evolutionary psychologist in the 1970's).