Prospective memory in young and older adults: The effects of task importance and ongoing task load

ABSTRACT

Remembering to perform an action in the future, called prospective memory, often shows age-related differences in favor of young adults when tested in the laboratory. Recently Smith, Horn, and Bayen (2012; Aging, Neuropsychology, and Cognition, 19, 495) embedded a PM task in an ongoing color-matching task and manipulated the difficulty of the ongoing task by varying the number of colors on each trial of the task. Smith et al. found that age-related differences in PM performance (lower PM performance for older adults relative to young adults) persisted even when older adults could perform the ongoing task as well or better than the young adults. The current study investigates a possible explanation for the pattern of results reported by Smith et al. by including a manipulation of task emphasis: for half of the participants the prospective memory task was emphasize, while for the other half the ongoing color-matching task was emphasized. Older adults performed a 4-color version of the ongoing color-matching task, while young adults completed either the 4-color or a more difficult 6-color version of the ongoing task. Older adults failed to perform as well as the young adults on the prospective memory task regardless of task emphasis, even when older adults were performing as well or better than the young adults on the ongoing color-matching task. The current results indicate that the lack of an effect of ongoing task load on prospective memory task performance is not due to a perception that one or the other task is more important than the other.

Keywords:

• Prospective memory
• Resources
• Cost
• Importance
• Multinomial modeling

The research was supported in part by Grant AG034965 from the National Institute on Aging. We thank Marisa Aragon, Andrew Bolisay, Ross DeForrest, Kathryn Dunlap, Immanuel Khachatryan, Sheila Meldrum, Amy Murray, Brittany Murray, Eric Olguin, Laura Randol, and Joe Tidwell for assistance with participant recruitment and data collection. This research was presented at the 2012 Cognitive Aging Conference in Atlanta, Georgia.

Notes

¹We used the color-matching ongoing task with words as the PM target events in order to match the procedures in Smith et al. (2012). Furthermore, this non-focal task was used by Smith et al., and we continued to do so in the current study, because the goal of both studies is to investigate the nature of age-related differences when these differences do emerge, thus it is appropriate to select a task in which age-related differences are more likely to occur. Finally, many real world prospective memory tasks are non-focal tasks and therefore understanding how young and older adults perform these tasks is an important question for this area of research.

²Smith et al. (2012), applied a multinomial model of event-based PM (Smith & Bayen, 2004, 2006) and some parameter estimates for the older adults in their easier (2-color) version of the task were very high. We designed the study to allow for application of the model and we were concerned that if we used the easier ongoing task for older adults and also emphasized the importance of the ongoing task, parameter estimates would reach ceiling, which could complicate interpretation of our findings. Therefore, we selected the 4-color version of the ongoing task for our older adult participants.

³Participants made a total of eight PM responses on trials other than the prospective memory target trials (i.e., PM responses on non-target trials). In no instances did these PM false alarms occur during the three trials immediately following any of the target trials.

⁴In response to reviewer suggestions, we conducted an ANACOVA with target recognition corrected hit rate as the covariate and PM performance as the dependent variable. The main effects of group, p < .001, and task emphasis, p = .01, remained significant. Although the contribution of the covariate was significant, F(1, 130) = 9.57, MSE = 0.01, p = .002, η_p² = .07, this did not account for the effects for group and task emphasis. In addition, while the young adults performing the more difficult ongoing task with instructions that emphasized the ongoing task showed a positive correlation between target recognition and prospective memory performance that approached significance, r = .37, p = .065, no other groups demonstrated such a relationship, all ps > .29.