476 Part VI Learning-Cognitive Theories
however, “it is all a matter of natural selection, since operant conditioning is an
evolved process, of which cultural practices are special applications” (p. 55).Natural Selection
Human personality is the product of a long evolutionary history. As individuals,
our behavior is determined by genetic composition and especially by our personal
histories of reinforcement. As a species, however, we are shaped by the contingen-
cies of survival. Natural selection plays an important part in human personality
(Skinner, 1974, 1987a, 1990a).
Individual behavior that is reinforcing tends to be repeated; that which is not
tends to drop out. Similarly, those behaviors that, throughout history, were benefi-
cial to the species tended to survive, whereas those that were only idiosyncratically
reinforcing tended to drop out. For example, natural selection has favored those
individuals whose pupils of their eyes dilated and contracted with changes in light-
ing. Their superior ability to see during both daylight and nighttime enabled them
to avoid life-threatening dangers and to survive to the age of reproduction. Simi-
larly, infants whose heads turned in the direction of a gentle stroke on the cheek
were able to suckle, thereby increasing their chances of survival and the likelihood
that this rooting characteristic would be passed on to their offspring. These are but
two examples of several reflexes that characterize the human infant today. Some,
such as the pupillary reflex, continue to have survival value, whereas others, like
the rooting reflex, are of diminishing benefit.
The contingencies of reinforcement and the contingencies of survival inter-
act, and some behaviors that are individually reinforcing also contribute to the
survival of the species. For example, sexual behavior is generally reinforcing to
an individual, but it also has natural selection value because those individuals who
were most strongly aroused by sexual stimulation were also the ones most likely
to produce offspring capable of similar patterns of behavior.
Not every remnant of natural selection continues to have survival value. In
humans’ early history, overeating was adaptive because it allowed people to sur-
vive during those times when food was less plentiful. Now, in societies where food
is continuously available, obesity has become a health problem, and overeating has
lost its survival value.
Although natural selection helped shape some human behavior, it is probably
responsible for only a small number of people’s actions. Skinner (1989a) claimed
that the contingencies of reinforcement, especially those that have shaped human
culture, account for most of human behavior.
We can trace a small part of human behavior... to natural selection and the
evolution of the species, but the greater part of human behavior must be traced
to contingencies of reinforcement, especially to the very complex social
contingencies we call cultures. Only when we take those histories into account
can we explain why people behave as they do. (p. 18)Cultural Evolution
In his later years, Skinner (1987a, 1989a) elaborated more fully on the importance
of culture in shaping human personality. Selection is responsible for those cultural