Forgetting rates for verbal, pictorial, and figural stimuli.

Literature on forgetting rates is reviewed and related methodological issues are discussed. Descriptive data from 50 subjects are provided for tests which were developed to assess forgetting rates for words, pictures and designs. The three tests are well-matched on initial learning at criterion and have comparable variance and skewness of score distributions. Forgetting rates were similar across the initial 10-min retention interval, but there was a more rapid loss of words than pictures and designs from 10 min to 2 hr, especially in male subjects. Memory for words and pictures steadily declined between 10 min and 48 hr, but there was no further loss for designs after 2 hr. These findings suggest that nonverbal memory storage is more stable than verbal memory storage over intervals of hours to days. Modest sex differences are discussed in terms of potential differences in organization of brain function. The potential utility of these tests in further elucidating the nature of memory impairment in clinical populations is addressed.