Array heterogeneity prevents catastrophic forgetting in infants

Abstract

Working memory is limited in adults and infants. But unlike adults, infants whose working memory capacity is exceeded often fail in a particularly striking way: they do not represent any of the presented objects, rather than simply remembering as many objects as they can and ignoring anything further (Feigenson & Carey 2003, 2005). Here we explored the nature of this “catastrophic forgetting,” asking whether stimuli themselves modulate the way in which infants’ memory fails. We showed 13-month old infants object arrays that either were within or that exceeded working memory capacity—but, unlike previous experiments, presented objects with contrasting features. Although previous studies have repeatedly documented infants’ failure to represent four identical hidden objects, in Experiments 1 and 2 we found that infants who saw four contrasting objects hidden, and then retrieved just two of the four, successfully continued searching for the missing objects. Perceptual contrast between objects sufficed to drive this success; infants succeeded regardless of whether the different objects were contrastively labeled, and regardless of whether the objects were semantically familiar or completely novel. In Experiment 3 we explored the nature of this surprising success, asking whether array heterogeneity actually expanded infants’ working memory capacity or rather prevented catastrophic forgetting. We found that infants successfully continued searching after seeing four contrasting objects hidden and retrieving two of them, but not after retrieving three of them. This suggests that, like adults, infants were able to remember up to, but not beyond, the limits of their working memory capacity when representing heterogeneous arrays.

Interference and memory capacity limitations.

“…In contrast, when items are presented sequentially one after the other, the network retains a buffer of the most recent items. These computational results fit well with the observation that participants in WM experiments tend to process items sequentially even when they are presented simultaneously (e.g., Liu & Becker, 2013;Vogel et al, 2006; but see Mance et al, 2012), as this might protect them from catastrophic interference (though infants might show catastrophic interference; Feigenson, 2005;Zosh & Feigenson, 2015). Be that as it might, Sengupta et al's (2014) and Knops et al's (2014) results show that mutual inhibition among neurons can lead to finite memory capacity limitations.…”

“…As a result, it is unclear to what extent Knops et al's (2014) subitizing response profile reflects voxels that are involved in small number processing as opposed to voxels that are not involved in small number processing, and that only support large number processing instead. or when they are made more distinctive, infants also succeed with a total of 4 objects (e.g., Feigenson & Halberda, 2008;Rosenberg & Feigenson, 2013;Zosh & Feigenson, 2015).…”

Mental Objects in Working Memory

“…The results of Zosh and Feigenson (2015) favor the latter account. Previous work combined with that of their 2015 paper showed that when the objects are all identical, fewer of them are retrieved than when the objects differ, suggesting that infants process the differences between objects.…”

“…The best performance has been obtained when the items are all different (Zosh & Feigenson, 2015). Infants 13-months old will search for the first two items and often will search for a third item.…”

Sequential Presentation Protects Working Memory From Catastrophic Interference

“…However, at least in infancy, some cognitive abilities such as number processing do show catastrophic performance limitations. For example, while infants reliably choose three over one food item, they are unable to choose between four and one food item; the most common explanation is that the number system used to process small numbers up to three is incompatible with the system used to process large numbers beyond three (e.g., Feigenson & Carey, ; Feigenson, Carey, & Hauser, ; Zosh & Feigenson, ). Furthermore, in line with long‐standing theorizing that our cognitive abilities might suffer from a general capacity limit (e.g., Cowan, ; Miller, ), this small number system might be related or even identical to working memory (WM) (Cowan, ; Piazza, Fumarola, Chinello, & Melcher, ), which also has important capacity limitations (e.g., Cowan, ; Fukuda, Vogel, Mayr, & Awh, ; Luck & Vogel, ; Vogel, Woodman, & Luck, ).…”