Working Memory for Item and Temporal Information in Younger and Older Adults

ABSTRACT

Two experiments examined age differences in mechanisms hypothesized to affect activation of item and temporal information in working memory. Activation levels were inferred from the ability to reject n-back lures matching items in different temporal positions. Information with the least decay had a performance advantage over less recent information, but was susceptible to the same temporal context errors found in all adjacent-to-target lure positions. Lures most distant from the current item showed a performance rebound. The pattern of increased magnitudes of age effects at adjacent-to-target positions indicated a reduction in older adults' working memory for temporal context information above and beyond item memory declines. Results overall support the emphasis on context information as a critical factor in working memory and cognitive aging.

Keywords:

• Working memory
• Temporal memory
• Age differences
• Context memory
• Cognition

ACKNOWLEDGEMENTS

This research was supported in part by the National Institute on Aging Grant (AG10593) awarded to the second author. The study was completed in partial fulfillment of the Ph.D. requirement of the first author. Portions of these data were presented at the 45th Annual Meeting of the Psychonomic Society (Minneapolis, 2004). The authors gratefully acknowledge Nicole Pukay-Martin and Jasmine Hudepohl for their assistance in programming, data collection, and scoring.

Notes

¹ Additional analyses were conducted to assess the similarity of lure patterns between the two n levels, when the lures were defined in terms of their distance from the current time (i.e., recency) and in terms of their distance from the target item. The results, however, did not show a qualitative difference between analyses; also, there were inconsistencies in the conclusions from Experiment 1 and Experiment 2. Thus, we were unable to draw any theoretically meaningful conclusions from these alternative analyses. The results of the relevant interaction terms are reported here.

We computed for each experiment, and for accuracy and RTs, ANOVAs with age, n level (2, 3) and lure position (4-, 5-, and 6-back) as factors. There were no significant task × lure position interactions in either experiment. The only interactions involved age. The accuracy analysis for Experiment 1 revealed an interaction of age and task (i.e., larger age differences for n level 3 compared to 2), and of age and lure position (i.e., steadily increasing accuracy as lure distance increased for older adults, but a leveling-off of performance as of the 5-back position for young). There were no such interactions with age in Experiment 2, however. The same patterns were mirrored in the RT data.

To examine lure position in relation to the target, we conducted analyses examining performance for lures that were identical for the two n-back tasks in terms of distance to the target position (i.e., n + 1 referred to 3-back lures for n level 2, and 4-back lures for n level 3; n + 2 referred to 4-back lures for n level 2, and 5-back lures for n level 3; and n + 3 referred to 5-back lures for n level 2, and 6-back lures for n level 3). There were no interactions between task and lure position. The only interaction from Experiment 1 was between age and lure position, characterized by significant improvement in accuracy for older adults as lure distance increased and the leveling-off of younger adult accuracy and RT after the n + 2 position. No interactions were found in the accuracy data of Experiment 2. The interaction between age and task in the RT data was driven by only younger adults showing a difference in RTs between the two n levels.

² Omitting new items from the ANOVA, as one anonymous reviewer suggested, resulted in identical findings with regard to the main effects and the interaction between age group and non-target item type. Thus, the interactions we report were not driven by the inclusion of new items in our analyses.