What Do Infants Remember When They Forget? Location and Identity in 6-Month-Olds’ Memory for Objects

Abstract

What does an infant remember about a forgotten object? Although at age 6 months, infants can keep track of up to three hidden objects, they can remember the featural identity of only one. When infants forget the identity of an object, do they forget the object entirely, or do they retain an inkling of it? In a looking-time study, we familiarized 6-month-olds with a disk and a triangle placed on opposite sides of a stage. During test trials, we hid the objects one at a time behind different screens, and after hiding the second object, we removed the screen where the first object had been hidden. Infants then saw the expected object, the unexpected other object, or the empty stage. Bayes factor analysis showed that although the infants did not notice when the object changed shape, they were surprised when it vanished. This finding indicates that infants can represent an object without its features.

Memory load affects object individuation in 18-month-old infants

“…This finding that the object-substance contrast supported individuation, whereas the object-object contrast did not, suggests that infants might not have remembered the objects in a three-object array in enough detail to allow the detection of a mismatch between what was hidden and what was retrieved. Indeed, previous research has also found that infants sometimes demonstrate accurate representations of the number of objects in a scene yet fail to accurately represent the features of the object(s) (Kibbe & Leslie, 2011;Wilcox & Schweinle, 2002). Our current results suggest that the degree to which object features are remembered, or are used to empower individuation, may depend on memory load.…”

Array heterogeneity prevents catastrophic forgetting in infants

“…If 6-month old infants can only represent a single object in working memory (Káldy & Leslie, 2005; Ross-Sheehy et al, 2003), then there is no possibility for heterogeneity between remembered objects to affect infants’ memory representations. Still, in other studies testing 6-month old infants’ memory for the features of two contrasting hidden objects (e.g., a circle and a triangle), infants showed evidence of remembering only the object that had been hidden most recently—that is, they did not exhibit catastrophic forgetting (Káldy & Leslie, 2005; Kibbe & Leslie, 2011). To determine whether the partial memory demonstrated by these infants required array heterogeneity, or also would have obtained with identical objects, will require comparing infants’ performance with contrasting versus identical objects.…”

“…Meanwhile, studies like those reported here measure observers’ ability to remember that a given number of objects existed in a particular location, regardless of their features. Previous research shows that infants sometimes remember that an object was present, even when its features are forgotten (Kibbe & Feigenson, submitted; Kibbe & Leslie, 2011; Zosh & Feigenson, 2012), raising the possibility that heterogeneity may differently affect infants’ memory for objects’ existence and for their features. In addition, the influence of array heterogeneity at different retention intervals remains to be explored.…”

Factors influencing infants’ ability to update object representations in memory

“…If infants can successfully update their working memory representation of what was hidden in each array, they should look longer at outcomes revealing two objects than at outcomes revealing three. We chose to test infants’ memory for the number of objects that had been hidden rather than for objects’ features or locations because previous work has shown that remembering an object’s existence is easier than remembering its identity (Kibbe & Leslie, 2011; Zosh & Feigenson, 2012), or remembering which object went where (Mareschal & Johnson, 2003; Newcombe, Huttenlocher, & Learmonth, 1999). Probing memory for objects’ existence therefore served as a liberal test of infants’ updating abilities.…”