Psychology differs from sociology, anthropology, economics, and political science, in part, by studying the behavior of individuals (alone or in groups) rather than the behavior of the groups or aggregates themselves. While psychological questions were asked in antiquity (c.f., Aristotle's De Memoria et Reminiscentia or "On Memory and Recollection"), psychology emerged as a separate discipline only recently. The first person to call himself a "psychologist", Wilhelm Wundt, opened the first psychological laboratory in 1879.
The root of the word psychology (psyche) means "soul" or "spirit" in Greek, and psychology was sometimes considered a study of the soul (in a religious sense of this term), though its emergence as a medical discipline can be seen in Thomas Willis' reference to psychology (the "Doctrine of the Soul") in terms of brain function, as part of his 1672 anatomical treatise "De Anima Brutorum" ("Two Discourses on the Souls of Brutes").
Until about the end of the 19th Century, psychology was regarded as a branch of philosophy. Experimental psychology, as introduced by Wilhelm Wundt in 1879 at Leipzig University in Germany, did not contain any religious implications. In the 1890s, Sigmund Freud invented and utilized a therapeutic method of uncovering repressed wishes, known as psychoanalysis. Since then, psychology typically considered primarily behavior (e.g., the behaviorism of John B. Watson and later psychologists), the mind (i.e., cognitive psychology), or both. Today it would be rare to find someone who considered psychology the study of immaterial minds, let alone souls. However, there are many psychologists who believe in the soul and bring spirituality into their psychological work. Of course, like all sciences that have broken off from philosophy, purely philosophical questions about the mind are still studied by philosophers; the name of the philosophical subdiscipline which studies those questions is philosophy of mind or philosophical psychology.
Experimental psychology, the field founded by Wilhelm Wundt and William James, focuses on general and basic questions concerning behavior, mental states, or both, including theories of pathology which are also important to clinical psychology.
Humanistic psychology emerged in the 1950s in reaction to both behaviorism and psychoanalysis. It stresses a phenomenological view of human experience and seeks to understand human beings and their behavior by conducting qualitative research. The humanistic approach has its roots in existentialist thought (see Heidegger, Nietzsche, Sartre and Kierkegaard). The founding theorists behind this school of thought are Abraham Maslow who presented a hierarchy of human needs, Carl Rogers who created and developed client centered therapy, and Fritz and Laura Perls who helped create and develop 'gestalt therapy'.
Clinical and counseling psychology both focus on understanding and treatment of behavioral or mental problems. Psychiatry is the medical field specializing in mental health issues, thereby overlapping with clinical psychology. Clinical and counselling psychologists often work in co-operation with psychiatrists, social workers, psychiatric nurses and 'lay' counselors. Psychiatrists are often involved in providing psycho-pharmacological care including antidepressant, antianxiety, antipsychotic and mood-stabilizing medication. Services aimed at mental or behavioral problems are also often provided by traditional healers and religious counselors. Fields such as neuroscience, political science, media studies and gender studies have also come to be seen as closely related to psychology.
Applied psychology is a more general term, referring not just to clinical applications but also to education, counseling, industry/organizational psychology, human factors and ergonomics, (and so on, please list if you can think of some).
During the third through sixth centuries in India, a branch of study developed within Buddhism that investigated the functions of the human mind, and the relationship of these to human behavior, mental illness, and methods for correcting delusory thinking that leads to suffering. This school was known as Yogacara (also known by the names Mind-only, Consciousness-only, etc).
In recent years and particularly in the United States, a major split has been developing between academic research psychologists in universities and some branches of clinical psychology. Many academic psychologists believe that these clinicians use therapies based on discredited theories and unsupported by empirical evidence of their effectiveness. From the other side, these clinicians believe that the academics are ignoring their experience in dealing with actual patients. The disagreement has resulted in the formation of the American Psychological Society by the research psychologists as a new body distinct from the American Psychological Association.
Topics in psychology
Major Nineteenth and Twentieth Century Schools of Thought
List of psychologists
Divisions and Approaches in Psychology (these might be overlapping, of course)