Picture superiority in free recall: Imagery or dual coding?

Abstract

Free verbal recall is generally higher for items presented as pictures than for items presented as words. Possible interpretations of this effect include differential verbal elaboration, superiority of nonverbal imagery as a memory code, and dual encoding favoring pictures. A series of experiments investigated the relative contributions of imaginal and verbal memory codes using incidental recall tasks in which the orienting task was designed to control the way items are encoded during input. Three experiments required subjects to encode words and pictures verbally, by writing or pronouncing the words or picture labels; or imaginally, by drawing or imaging the picture or object suggested by the word. Two further experiments involved a probability learning task which required no encoding reaction to pictures or words, but an analogue of imaginal and verbal coding was provided in one experiment using picture-picture, picture-word (or word-picture) and word-word repetitions. Recall tests following these manipulations consistently yielded much higher recall for pictures than for words under all conditions except when subjects imaged to words. Strong support was also found for the hypothesis that image and verbal memory codes are independent and additive in their effect on recall. In addition, the contribution of imagery appeared to be substantially higher than that of the verbal code. Thus the usual superiority of pictures in free recall is best explained by dual encoding, or a combination of image superiority and dual coding, both of which are ordinarily favored when items are presented as pictures.