Age and binding within-dimension features in visual short-term memory

Older adults have difficulties in binding information in long-term memory (e.g. objects with colours). The effect of age on visual short-term memory (VSTM) binding is less well understood. Recent evidence has suggested that older adults' VSTM for colours bound to shapes or for locations bound in configural representations may be preserved. In two experiments we investigated whether this lack of an age effect on VSTM for bound features can be reproduced when features are drawn from the same dimension (i.e. colour-colour binding) and when spatial clues are not available. Younger and older adults were presented with two sequential arrays of unicoloured or bicoloured objects and their accuracy in detecting changes between arrays was used as the measure of memory performance. Memory was assessed using a change detection paradigm for unicoloured objects and for bicoloured objects with changes in colour conjunctions (i.e. colours swapping between objects) or with changes in non-conjunctive colours (i.e. colours replacing colours in the study array). Both young and older adults were less accurate at remembering objects defined by colour conjunctions than unicoloured objects or objects composed of two non-conjunctive colours (Experiment 1). Increasing task demands in terms of memory and perceptual load had no greater effect on the older than the younger adults (Experiment 2). We suggest (1) that colours were not integrated into single units in VSTM; (2) that remembering the binding between colours has a cost; and (3) that neither of these effects are age-dependent.