This research on factors influencing verbal learning and retention has used new techniques, attacked new problems, and tested new theories while trying to keep the experiments systematic. Studies conducted involved (1) the effect of varying the length of the intertrial interval on the learning and retention of different types of learning tasks; (2) differences in recall between massed repetitions and distributed repetitions; (3) evaluations of certain aspects of the "forgetting theory;" (4) "meaningfulness" as a task variable influencing the rate of verbal learning; (5) memory viewed as an ensemble of attributes--a position influenced by four lines of research dealing with rule learning to encode and decode relatively low meaningful verbal units, frequency as a discriminative cue, implicit associative responses evoked when a common word is presented the subject for learning, and position information; (6) the influence of similarity, both meaningful and formal on verbal learning; (7) the bidirectional extent of paired-associate learning; and (8) experiments which both clarified methods and exposed "artifacts" in the work of others. Listings of published reports concerning each of the studies are included. (JMC)