Hartley, David (1705-1757) Hartley studied at Cambridge and was prepared to follow his father’s footsteps (minister) but his interest in biology led him to seek a medical degree. He is considered to be one of the first physiological psychologists. In 1749, Hartley published a combination of psychological and theological insights entitled Observations on Man, His Frame, His Duty and His Expectations. Like Newton, Hartley dismissed Descartes’ contention that nerves are hollow. He maintained that sensations cause vibrations in the nerves which in turn cause vibrations in the brain. These vibratuncles result in ideas (faint vibrations) and memory (reactivating the original vibrations).