The definition of Psychology

The official definition of Psychology has changed multiple times over the past century and a half. After the first psychological experiment was conducted, in 1879 by William Wundt, psychology became "the science of mental behavior." For 40 years after Wundt's experiment psychologists focused on the human thought process. Then, in 1920, psychologist began to study humanistic behavior. Thus the definition officially changed to become "the science of observable behavior." Psychologist believed they could not accurately study the actions of the mind, so they had to focus on behaviors they were 100% able to observe. In 1960, after technology developed and machines were invented that allowed psychologists to accurately study the brain, psychology officially became "the science of behavior and mental process." 

-Natanel Brakha