Spacing effects in picture memory

Three experiments were conducted to capitalize on the conclusion of Shaffer and Shiffrin (1972) that complex visual scenes are not rehearsed in testing the hypothesis that the effect of spacing on memory is due to rehearsal. In Experiment I, a list of vacation slides was presented in which both the number of repetitions and the spacing of repetitions were varied. Subsequent frequency judgments showed an effect of spacing much like that found using verbal materials. In Experiments II and III, effects of filled and unfilled spacing intervals were compared, and it was concluded that the spacing effect is primarily a function of the duration of the spacing interval. No evidence was found to support the notion that pictures are rehearsed. Rehearsal apparently cannot play the key role in an adequate, completely general explanation of the spacing effect.