Curt Richter

Curt Paul Richter (February 20, 1894 – December 21, 1988) was a biologist, psychobiologist and geneticist at Johns Hopkins University. Richter identified the hypothalamus as a "biological pacemaker" involved in sleeping and wakefulness.
Richter induced need states in experimental animals by depriving them of substances essential to survival, or manipulating the hormone levels, and showed that these need states generate appetites, and behaviours precisely fitting the animal's need even if the animal had never before experienced the need; demonstrating genetic programming of behaviour. He also triggered other pre-programmed behaviours, such as nest building, by manipulating hormone levels.