Age-related deficits in cognitive functioning are not mediated by time of day.

Few studies have examined whether cognitive performance of adults is influenced by the time of day in which they are tested. It has been suggested (May, Hasher, & Zacks, 1993) that some of the reported age differences in performance may be attenuated when older adults are tested during their optimal time, and younger adults are tested during their nonoptimal time. A total of 100 adults (20 to 78 years of age) participated in this study to investigate whether time of day and/or age are significant predictors of cognitive performance. Three tasks measuring crystallized and fluid types of abilities were employed. Hierarchical regression analyses revealed that age was a significant predictor for two of the tasks, whereas time of day of testing did not predict performance for any of the three types of tasks. The results suggest that time of day influences may be limited to specific types of cognitive abilities.

Age and decision strategies in running memory for speech: effects of prosody and linguistic structure.

Young and elderly adults heard recorded passages of English prose spoken with and without normal prosody, and passages that were devoid of either linguistic or prosodic structure. Subjects were instructed to interrupt the speech input at points of their choosing for immediate recall on a segment-by-segment basis. For both age groups segmentation strategies varied with type of speech materials as did their levels of recall accuracy. Age differences in recall performance were diminished by the presence of normal prosody, an effect only partially attributable to the use of prosody to detect linguistic boundaries at the surface level.

Does the capacity of working memory change with age?

Young and elderly adults were compared for recall performance on simple digit and word spans (traditional tests of primary memory), versus a "loaded" auditory word span test designed to emphasize working memory capacity. Although digit spans were identical for the two age groups, there were small but significant age differences in word span, and even larger differences in working memory performance. An analysis of correlations between span measures and verbal ability scores supported the position that working memory loading represents a special problem for the elderly.