Implications of aging, lexicality, and item length for the mechanisms underlying memory span.

Hulme, Maughan, and Brown (1991) provided evidence that the contribution of long-term memory to memory span performance was additive to the contribution of rehearsal rate (e.g., Baddeley, 1986). The present study further explored the relationship between these two contributions in younger and older adults. Speech rates and spans for short, medium, and long words and nonwords were obtained from subjects. Older adults had slower speech rates and smaller spans than did younger adults. Both groups' data were fit well by linear functions relating speech rates to spans. However, the slope of the function that relates speech rate to memory span was greater for words than for nonwords. This finding supports the idea that long-term memory, as well as rehearsal rate, contributes to span performance, and that this contribution is not simply additive.