Our bodies evolved over eons, slowly calibrating to the African savanna on which 98 percent of our ancestors lived and died. So, too, did our brains. Evolutionary psychology postulates that the mind is shaped by pressure to survive and reproduce. We jealously guard romantic partners and cherish our closest relatives above all others, lest we fail to pass on our genes.
Behaviorism seeks to identify observable, measurable laws that could explain all of human behavior. Although psychology now pays more attention to the inner landscape of emotions and thought, behaviorism has had a durable influence on everything from animal training to parenting techniques to the bonuses financial managers receive.