Determinants of Working Memory Performance

This dissertation investigated different factors contributing to age differences in working memory (WM) performance. Younger and older adults participated in five experiments, four on visuospatial WM (VSWM) and one on verbal WM. All addressed methodological issues that may differentially lower older adults’ performance. Experiments 1a and 1b manipulated the administration of a VSWM span task, with participants performing the task under either an ascending format (shortest sets presented first), or an interference-reducing descending format (longest sets presented first). Older adults’ performed significantly better in the descending compared to ascending format, consistent with an age-related susceptibility to proactive interference (PI). By contrast, younger adults did better in the ascending compared to descending condition, possibly due to their ability to benefit from practice and strategy use when easier trials are presented first. Experiment 2 considered how the similarity of task material influenced the build-up of PI and whether or not the combination of two PI-reducing manipulations (i.e., descending format and distinct trials) would further improve older adults’ performance. Distinctiveness helped older adults on the ascending format; however, combining distinct trials and a descending format provided no additional benefit. Experiment 3 considered whether or not synchronizing a VSWM task with an individual’s circadian arousal pattern would moderate interference effects, with the task administered at a peak or off-peak time of day. Peak-time administration improved older adults’ performance on the descending, but not the ascending, condition. Experiment 4 investigated the possibility that the serial order requirement of many WM tasks contributes to age differences in performance. Younger and older adults participated in a verbal WM span task – Operation Span - under either serial order or free recall instructions. Typical age differences were found when order but not free recall was required. Further analyses of the order condition data revealed that older adults were, in fact, recalling the items just as well as young adults, only not in the correct order. Taken together, the findings strongly suggest that age differences found on typical WM span tasks are influenced by numerous factors, such as task presentation, individual circadian arousal patterns, material similarity, and recall instructions.Ph