Temperamental characteristics of human beings, to the extent that they are not the result of inheritance, depend largely, if not entirely, on dispositional learning, a kind of learning that is, in large part, the sum of many experiences with reward and frustration, and that occurs without specific awareness. Dispositions in humans that depend on a history of inconsistent reinforcement (intermittent frustration) may be subject to the same etiological principles that, as we have seen, operate in animals. I have taken the opportunity in several places in this book to give examples of how such principles derived from animal research may apply to humans.

It now seems safe to assert, on the basis of research not only with animals but also with humans, that a connection exists between negative emotional states and frustrative events; between patterns of inconsistent reward and frustration (or smaller and larger reward or immediate and delayed reward) for what seems to be the same behavior (or effort) and persistence; and between principles of instrumental learning derived from such schedules of reward and frustration and accounts of helplessness and depression. In this book, there has been an attempt to show that there is now some basis in learning theory, and particularly in frustration theory, for coming closer to a comprehension not only of the conceptual mechanisms of these relationships, but also of their sequence in development and, to an early approximation at least, their neural underpinnings.