Levin, J. R. & Lesgold, A. M. (1978). On pictures in prose. Educational Communication and Technology Journal, 26(3), 233-243.

For some time now, researchers and educators have questioned the value of pictures for prose-learning. However, there is abundant empirical evidence to document the positive value of pictures. Consistent learning gains are associated with the use of pictures when experiments adhere to these five ground rules: (1) prose passages are presented orally; (2) the subjects are children; (3) the passages are fictional narratives; (4) the pictures overlap the story content; and (5) learning is demonstrated by factual recall.