Continuities and discontinuities in working memory representations of collections over ontogeny

Abstract

Working memory, or the ability to maintain and manipulate information such that it can be used to guide behavior, is known to be severely capacity limited, in most circumstances, to about 3-4 objects. Both infants and adults have the ability to surpass these limits by encoding to-be-remembered items in groups or collections, exploiting statistical regularities or conceptual information to devise more efficient coding schema. Despite progress made toward understanding continuities in working memory, little is known about how changes over development interact with the ability to employ maximally efficient mnemonic data structures. Paper 1 demonstrates that although adults can encode at most three mutually exclusive collections that accrue sequentially over time, they can circumvent this limit when items overlap in features (e.g. red and blue circles and triangles) and statistical regularities are introduced among collections defined by a single visual feature (e.g. most red items are triangular and not circular). Adults' performance suggests they are able to encode items from intersecting collections hierarchically and exploit statistical regularities among collections to reconstruct the numerosities of up to six collections in parallel, exemplifying how efficient coding can radically enhance working memory. Paper 2 demonstrates that young preschoolers can also represent three mutually exclusive collections that accrue in an intermixed fashion over time. Results show that the ability to surpass this capacity limit by hierarchically reorganizing collections and exploiting statistical regularities among them develops between the ages of three and seven. These results are discussed in the context of executive function development. Paper 3 provides evidence that computations of average size and orientation rely on qualitatively different processes with distinct developmental trajectories. Experiment 1 demonstrates that while the presence of additional identical elements in an array detrimentally impacts 6-month-olds' representations of element size, it improves the precision with which infants represent orientation. Experiment 2 demonstrates that performance is not affected when infants' attention is cued to a single item within arrays. These results are discussed in the context of the development of controlled attention.