John B. Watson, the founder of behaviorism, believed that human personality is created not by inner forces but by environmental stimuli. We are the products, according to Watson, of conditioned responses. Fear stems from loud noises or the sudden loss of physical support; rage from physical constraint; love from the stroking of erogenous zones...

In 1920, Watson was removed from his post at Johns Hopkins when it was discovered that his young research assistant, Rosalie Rayner, was also his mistress. In the ensuing divorce suit, Watson's wife submitted as evidence some of his correspondence with Rayner (which the Baltimore newspapers gleefully quoted). Among his most memorable romantic lines: "My total reactions are positive and towards you..."