Regarding cognitive effects of illustrations in text, Peek has concentrated on studies of retention effects. Her general
conclusions are that “retention of depicted text information is facilitated, whereas unillustrated text is not,” and “with
growing delay, subjects tend to base their retention-test responses on what they have seen in the pictorial supplements”
(p. 128). In other words, when pictures and text are used together, retention is facilitated, and pictures help delayed
recall more than immediate recall.