The way we view human motivation is new and difficult to find in earlier societies. Why? Montaigne instituted self-reflection, in effect an interior world. Was this the beginning of modern psychology?
The conventional wisdom is that the modern science of Psychology begins with Wilhelm Wundt, who aimed to scientifically study the structure of thought through introspection (“structuralism”). He is the first person to call himself a “psychologist" distinguishing Psychology from Philosophy and the science of Physiology. He founded his lab in 1879. Another founder of Psychology would be William James, who first published a study of emotions in 1884 about their purpose (“functionalism”). Many laypersons consider Freud the “father of psychology” but his 'theory' is just wild, often untestable, speculation. For the origins of some of the ideas modern psychology studies - but without being actual science - you can go back to the earliest philosophical writings. Some Philosophers like to attribute the origins of Psychology to Aristotle, who certainly speculated about the nature of personality (“psychology”) much like he speculated about falling objects (“physics”). You can find speculations that go back much further, such as ancient China, Egypt, and Israel. Best wishes with starting to explore Psychology, Stanley! ~ Kevin