Psychology is the study of the mind. Typically, psychology focuses on the human mind, but animal minds are also sometimes studied.
Just like much of the research on animal psychology also applies to humans, research on human psychology may inform how we develop and use AI.
Modern psychology began with the Freudian model of psychoanalysis, which quickly supplanted the prevailing pseudosciences like phrenology. Psychoanalysis is now largely obsolete, and has been replaced by other schools. The most prominent among these include:
Behavioral Psychology, which focuses on observable learning and behavior.
Humanistic Psychology, which focuses on theories of self-actualization and self-help.
Cognitive Psychology, which uses modern research on brain anatomy and other subjects to create theories about how the brain learns, develops, and makes decisions.
From an academic standpoint, much of the content of Lesswrong can be described as trying to implement the results of Decision Theory to people's daily actions using knowledge of human psychology. Sometimes, this involves overriding our native tendencies. Other times, it involves using them to our advantage.