1.0 IntroductionThere are many meanings for the word "psychology" which literally means, according to Wikipedia, the study of the soul and in Latin the words psychologia were first used times by the Croatian humanist and Latinist Marko Marulić in 1835. his book, “Psichiologia de rationeanimae humanae” around the end of the 15th century or the beginning of the 16th century. Work psychology in English was created by Steven Blankaart in 1694 and is called, in the physical dictionary, "anatomy" treatment for the body and "psychology" treatment for the soul. Did you know that the study of psychology dates back to the ancient civilizations of Egypt, Greece, China, India and Persia. According to history, Greek philosophers like Thales, Plato, and Aristotle wrote about the workings of the mind in the written works. According to the theory of Greek doctors, psychology is more of a mental disorder. Psychology is the study of mental function and behaviors and is usually done by people with knowledge, as it needs discipline and academia to be able to understand. Psychologists are individuals who have needs as a therapist and are able to understand individual needs, sometimes they are also called social, behavioral or cognitive scientists. Psychologists try to understand the function of the human brain in terms of social behavior and also the process or biological behavior will be explored by them. It is not easy to be them because they have to learn the concept of the brain, personality behavior, emotion, including understanding the reasons for behavior for example; family history, psychological history and other areas which are important for them to understand their patient, sometimes they believe that whenever this happens, most patients are unconscious, which makes them not know... in the middle of the paper. .....ch they demonstrated that emotional reactions could be classically conditioned in people.• 1929 - Edwin Boring's book, A History of Experimental Psychology, is published. Boring was an influential experimental psychologist who was dedicated to the use of experimental methods in psychological research.• 1955 - Lee Chronbach published Construct Validity in Psychological Tests, which popularized the use of construct validity in psychological research .Psychologists who use this type of research methods involve very scientific tools to study human behavior. Experiment methods use the basic standard over other techniques. The main thing in conducting a psychology experiment is to randomly assign participants into groups, define variables, develop hypotheses, manipulate independent variables, and measure dependent variables..