Adult Age Differences in Working Memory Capacity: Spared Central Storage but Deficits in Ability to Maximize Peripheral Storage

For the first time, we quantify capacities of working memory in young and older adults in a dual-task situation, addressing whether older adults have diminished central or peripheral capacity in working memory. Across 2 experiments, 63 young and 63 old adult participants studied visual arrays of colored squares and sequences of unfamiliar tones in quick succession and were instructed to attend to one or both modalities. Memory was assessed with a single-probe change-detection task. We used a recently developed capacity-estimate model to partition participants' overall working memory capacity into 3 components: a peripheral component dedicated to visual information regardless of attention instruction; a peripheral component similarly dedicated to auditory information; and a central component allocated to either modality, or shared between both, depending on attention instruction. Capacity estimates of the peripheral components were consistently smaller in the older adults than in the young adults. but the central component was stable across both age groups. We contend that older adults are impaired in their ability to strategically encode information in ways that younger adults use to increase peripheral storage, a kind of storage that is immune to loss through bimodal attention costs.