There is a large body of comparative research on learning from text with and without pictures. Almost all of the studies examine only the impact on cued recall and use traditional experimental designs, of the type criticized by Clark (1983). However, there is consensus among the reviews of this research that pictures have positive effects under certain conditions. Pressley (1977), Schallert (1980), and Levie and Lentz (1982) generally concur that the use of pictures with text increases recall, particularly for poor readers, if the pictures illustrate information central to the text, and when they represent new content that is important to the overall message, or when they depict structural relationships mentioned in the text. The problem with this type of research is that it does not reveal the mechanism by which pictures and text influence the learning process.
The four studies below examine processes of comprehension and learning with text and pictures. In brief, it appears that the use of both symbol systems facilitates the construction of the textbase and the mapping of it onto the mental model of the situation. This is particularly facilitative for learners who have little prior knowledge of the domain.