Frustration theory--many years later.

The role of frustration in learning theory, in the invigoration of behavior and in the development of learned persistence and discrimination learning, is conceptualized. This and other phenomena are facets of the larger explanatory domain of what has come to be known as frustration theory, a theory that has guided the author's own research--from behavioral to developmental to psychobiological --until the present time and has had some influence on the research of other investigators. This is a commentary on the 1st of several published theoretical papers on frustration theory.