Storage and processing in working memory: Assessing dual-task performance and task prioritization across the adult lifespan

Abstract

There is a theoretical disagreement in the working memory literature, with some proposing that the storage and processing of information rely on distinct parts of the cognitive system and others who posit that they rely, to some extent, on a shared attentional capacity. This debate is mirrored in the literature on working memory and aging, where there have been mixed findings on the ability of older adults to perform simultaneous storage and processing tasks. We assess the overlap between storage and processing and how this changes with age using a procedure in which both tasks have been carefully adjusted to produce comparable levels of single-task performance across a sample (N = 164) of participants aged 18-81. By manipulating incentives to perform one task over the other, this procedure was also capable of disentangling concurrence costs (single- vs. dual-task performance) from prioritization costs (relative payoffs for storage vs. processing performance) in a theoretically meaningful manner. The study revealed a large general cost to serial letter recall performance associated with concurrent performance of an arithmetic verification processing task, a concurrence cost that increased with age. For the processing task, there was no such general concurrence cost. Rather, there was a prioritization effect in dual-task performance for both tasks, irrespective of age, in which performance levels depended on the relative emphasis assigned to memory versus processing. This prioritization effect was large, albeit with a large residual in performance. The findings place important constraints on both working memory theory and our understanding of how working memory changes across the adult lifespan. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Figure 1 .

The general trial procedure.

Figure 2 .

Span estimates for the memory task split by presentation/recall format across 5 age-groups. Points are individual scores (jittered within groups to reduce overlap) with means and within subjects 95% confidence intervals overlaid. Note: Age Group 1 = 18–30; 2 = 31–43; 3 = 44–56; 4 = 57–70; 5 = 71–81.

Figure 3 .

Span estimates for the processing (arithmetic verification) task split by session across 5 age-groups. Points are individual scores (jittered within groups to reduce overlap) with means and within subjects 95% confidence intervals overlaid. Note: Age Group 1 = 18–30; 2 = 31–43; 3 = 44–56; 4 = 57–70; 5 = 71–81.

Figure 4 .

Accuracy on memory and processing tasks across point allocation for the two presentation and recall formats. Lines from individual participants are given with means and 95% CIs. Condition numbers refer to the number of points allocated to the memory task (P) in that condition with the number of points allocated to processing being 100 − M. The 0 condition is the single task processing measure and the 100 condition is single task memory.

Figure 5 .

Mean accuracy on memory and processing tasks binned into 5 age groups. See Figure 4 for an explanation of condition numbers.