The one-trial learning controversy and its aftermath: remembering Rock (1957).

In 1957 Irvin Rock published an article in the American Journal of Psychology igniting a controversy that dominated the field of verbal learning for the next 8 years before mostly burning out. Rock published 2 paired-associate learning experiments in which he compared performance of a control group that learned a constant list of pairs to the criterion of one perfect trial with an experimental group in which forgotten pairs on each trial were dropped and replaced on the next trial with new pairs. That is, on each trial for experimental subjects, pairs that were correctly recalled were maintained in the next trial, whereas pairs that were not recalled were dropped and replaced randomly with new pairs from a large pool. Surprisingly, Rock found that the 2 groups took the same number of trials to reach criterion. He concluded that learning occurred not with a gradual, incremental increase in strength of memory traces but rather in an all-or-none fashion. Rock's conclusions rocked the world of verbal learning, because all theories followed a gradualist assumption. However, Estes (1960) published research that led him to the same conclusion shortly thereafter. We recount these developments and discuss how the verbal learning establishment rose up to smite down these new ideas, with particular ferocity directed at Rock. Echoing G.A. Miller (1963), we conclude with a note of sympathy for Rock's and Estes's positions and muse about why their work was so summarily dismissed. The important question they raised--the nature of how associations are learned--remains unanswered.