Effects of spacing and embellishment on memory for the main points of a text.

An advantage has been found for acquiring textbook knowledge by studying textbook summaries rather than reading the original prose (Reder & Anderson, 1980). Three studies are presented that help to establish the cause of the summary advantage. One possible cause is that reading summaries allows the subject to reread the main points at spaced intervals, and spaced practice is superior to massed practice. A second possible cause is that the presence of details distracts the subject’s attention away from the critical ideas that should be attended to. In Reder and Anderson (1980), these two factors were confounded, but they are unconfounded in the present studies. The results indicate that both possible causes, spaced practice and the absence of details, have significant, independent, and positive effects on retention of the central ideas of a passage.