Mankind is relatively free from biological instincts, drives and predispositions. Rather than relying on instinctual behavior, the vast repertoire of our social behavior is learned. Sociocultural systems thus have dramatic impact on how people satisfy these biopsychological needs. People need to eat and will generally opt for diets that offer more rather than fewer calories and proteins and other nutrients. People cannot be totally inactive, but when confronted with a given task, they prefer to carry it out by expending less rather than more human energy.
People are highly sexed and generally find reinforcing pleasure from sexual intercourse.
People need love and affection in order to feel secure and happy, and other things being equal, they will act to increase the love and affection others give them. Harris justifies this list with two observations. Second, the list should be judged not on its inclusiveness but on the adequacies of theories it helps to generate. But rather than enumerate all, the focus is on a parsimonious list of assumptions needed to account for the similarities and differences of human behavior. It is through socialization and interaction that we learn culturally approved ways of satisfying these biopsychological needs.