Psychology's Roots

First of all we need to see Psychology as a science. The study of behavior ( anything an organism does) and mental process ( experiences).
The roots of Psychology go far back in History to Asia, China, the Middle East and Europe. Many people in those regions wondered about humans and tried to understand the human nature, so they looked carefully at our bodies and how our mind works in relationship with it. Buddha and Confucius focused over 2000 years ago on power and origin of ideas. The ancient Hebrews, Socrate, his student Plato, and Plato's student Aristotle have thought about whether mind and body are connected or distinct, or whether human ideas are innate or results from experiences.
Rene` Descartes and John Locke reengaged in the 1600s, aspects of those ancient debates and Locke coined his famous description of the mind as a "white paper".
Empiricism is the view that pretty much knowledge comes from experiences and that science should rely on observations and experimentation which have been the ideas of Francis Bacon and Locke.
Psychology was born in the 1800's in Leipzig, Germany by Wilhelm Wundt which he did by doing the first real experiment.
Edward Bradford Titchner tried to do more experiments and through that attempt to understand now mental and behavioral processes help us to adapt, survive and flourish.
William James and other functionalist tried to explain why we do what we do.
Psychology was a "science of mental life" until the 1920s. John B. Watson and F.B. Skinner, which were 2 American behaviorist, changed the focus of Psychology to the study of observable behavior. It was in the 1960s when humanistic psychologists draw attention to the importance of environmental influences, personal growth, and the needs for love and acceptance. Also the focus of psychology's interest has been refocused by the cognitive revolution to mental processes, with special attention to perception, information processing, and memory. Todays Psychology views itself a a "science of behavior and mental process" which cognitive neuroscientists are trying to tell us.
Contemporary Psychology
The big debate in Psychology is whether nature (view of Plato and Descartes, gene) or nurture ( view of Aristotle and Locke, all other influences, from conception to death) was more important. Charles Darwin proposed a mechanism - the principle of natural selection - by which nature selects chance variations that enable organism to survive and reproduce in particular environments. Now they believe that every psychological event is simultaneously an biological event.
The biospsychosocial has 3 level of analyses, the biological, the psychological, and the social-cultural level. There are many different perspectives of how psychologists study human behaviors and mental processes ( including the neuroscientific, evolutionary, behavior genetics, psychodynamic, behavioral, cognitive and social - cultural perspective)
Psychology's subfields encompass basic research ( often done by biological, development, cognitive, personality, and social psychologists), applied research ( sometimes conducted by industrial/organizational psychologists), and clinical application ( the work of counseling and clinical psychologists).
Clinical psychologists study, asses, and treat ( with psychotherapy) people with psychological disorders, psychiatrists also study, asses, and treat people with disorders, but they are medical doctors who can prescribe medical as well as offer psychotherapy.
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So that would be it. I might as well put a little dictionary on those words up there soon so you can understand the concept better, unless you know all these words anyways. If you have any questions in this topic then comment and I'll respond as soon as I can. I'm going to put up an review on every unit i'm going to read, which is really exciting. I hope you're interested!
Credit:
Picture, Wilhelm Wundt