No abstract

Theories of working memory often disagree on the relationships between processing and storage, particularly on how heavily they rely on an attention-based limited resource. Some posit separation and specialization of resources resulting in minimal interference to memory when completing an ongoing processing task, while others argue for a greater overlap in the resources involved in concurrent tasks. Here, we present four experiments that investigated the presence or absence of dual-task costs for memory and processing. The experiments were carried in an adversarial collaboration in which researchers from three opposing theories collaboratively designed a set of experiments and provided differential predictions in line with each of their models. Participants performed delayed recall of aurally and visually presented letters and an arithmetic verification task either as single tasks or with the arithmetic verification task between presentation and recall of letter sequences. Single- and dual-task conditions were completed with and without concurrent articulatory suppression. A consistent pattern of dual-task and suppression costs was observed for memory, with smaller or null effects on processing. The observed data did not fit perfectly with any one framework, with each model having partial success in predicting data patterns. Implications for each of the models are discussed, with an aim for future research to investigate whether some combination of the models and their assumptions can provide a more comprehensive interpretation of the pattern of effects observed here and in relevant previous studies associated with each theoretical framework.

Three experiments investigated younger (18-25 yrs) and older (70-88 yrs) adults' temporary memory for colour-shape combinations (binding). We focused upon estimating the magnitude of the binding cost for each age group across encoding time (Experiment 1; 900/1500 ms), presentation format (Experiment 2; simultaneous/sequential), and interference (Experiment 3; control/suffix) conditions. In Experiment 1, encoding time did not differentially influence binding in the two age groups. In Experiment 2, younger adults exhibited poorer binding performance with sequential relative to simultaneous presentation, and serial position analyses highlighted a particular age-related difficulty remembering the middle item of a series (for all memory conditions). Experiments 1-3 demonstrated small to medium binding effect sizes in older adults across all encoding conditions, with binding less accurate than shape memory. However, younger adults also displayed negative effects of binding (small to large) in two of the experiments. Even when older adults exhibited a greater suffix interference effect in Experiment 3, this was for all memory types, not just binding. We therefore conclude that there is no consistent evidence for a visual binding deficit in healthy older adults. This relative preservation contrasts with the specific and substantial deficits in visual feature binding found in several recent studies of Alzheimer's disease.

Relative to younger adults, older adults tend to perform more poorly on tests of both free recall and item recognition memory. The age difference in performance is typically larger for recall tasks relative to those involving recognition. However, there have been reports of comparable age-related differences in free recall and item recognition performance. Further, a differential performance cost does not necessarily mean that processes involved in recall are specifically affected by age. Here we present a meta-analysis of 36 articles reporting 89 direct comparisons of free recall and item recognition in younger and older groups of participants. Standardized effect sizes reveal that age differences are larger for recall tasks (Hedges' g = 0.89, 95% confidence intervals [0.75, 1.03]) than for recognition tasks (0.54, [0.37, 0.72]). Further, Brinley analyses of the data suggest that distinct functions are needed to relate younger and older performance for the two tasks. These functions differ in intercept pointing to a disproportionate age difference in recall relative to recognition. This is in line with theories of memory and aging which posit specific deficits in processes related to search and retrieval from memory.