The theoretical functions of external feedback in SR and closed loop models of verbal learning are presented. Contradictory predictions from the models are tested with a three by three factorial experiment including three types of feedback and three amounts of rehearsal. There were 90 adult students run individually and they were required to learn 39 sentences verbatim. The results were: (1) feedback facilitated learning when it followed wrong responses; (2) feedback had no effect on learning following right responses; and (3) feedback consisting of both the stimulus and the response was superior to "no feedback" whereas feedback consisting of only the response did not differ from "no feedback". The findings are discussed in relation to the two learning models and programmed instruction. (Author)