Aristotle studied human consciousness and decided it was in the heart, but this was not actually what he meant.
Charles Darwin came up with functionalism.
Muhammad ibn Zakariya al-Rhazes A.K.A. Rhazes was one of the first to describe mental illness and also treated patients as a psych ward.
“Interpretation of Dreams” was a book made by Sickman Freud. He smoked and got jaw cancer and he commit suicide with methane at age 30.
B.F. Skinner put rats, pigeons, and babies in boxes and conditioned them to perform certain behaviors. Near when he escaped to England, he published a book called “Behaviors of Organisms”.
Today’s formal psychology definition - The science of behavior and mental processes.
My Google Doc: https://docs.google.com/document/d/1TmtXMVeuT95tkl1Ba_M5dIBQv0eL1yNuaR5MjeHBRzo/edit