Underused but not lost: adaptive working memory usage in aging

Background Working memory (WM) declines with age, but most studies quantify this decline by estimating capacity: how many items can be retained under maximal demand. WM capacity, however, provides only a partial window into everyday WM. What also matters is WM usage: how much people choose to rely on WM during natural behaviour. We ask whether usage differs between healthy older and young adults, and whether older adults retain flexibility to increase usage when environmental demands change. Methods One hundred participants (50 younger adults, mean age 23; 50 older adults, mean age 70) completed a virtual-reality object-copying task, reconstructing spatial arrays seen in a model display by carrying objects between a resource area and a workspace. Environmental demands were manipulated by varying the physical cost of consulting the model, yielding low vs high movement-effort conditions. WM usage, complete memory failures, and encoding time were compared between age groups and movement-effort conditions using linear mixed-effects models. Results Older adults showed lower WM usage than younger adults across effort conditions, and this age difference widened when environmental demands increased. Both groups increased WM usage under higher demands, but the increase was fourfold larger in younger adults. Interestingly, higher demands also reduced complete memory failures, with older adults showing the larger absolute reduction. Thus, older adults showed reduced baseline usage but retained adaptive flexibility to increase usage when demands changed. Conclusions Healthy older adults show reduced WM usage during natural behaviour but retain some flexibility. Environmental demands can increase WM usage and reduce complete memory failures, suggesting a tractable route for supporting everyday WM in ageing.