Remembering in the Context of Internal States: The Role of Sleep for Infant Memory

Abstract

Research with adults has shown that a person's internal context, or state, influences how memory functions. This factor is rarely considered in research on infant memory, in part because of the practical and ethical difficulties of manipulating these variables in infants. In this article, we argue that models of infant memory will remain limited in scope and accuracy if the internal context of participants is not considered. As a case in point, we present emerging literature on sleep-dependent memory. Our review shows that for infants, timely sleep after a learning experience helps them retain and further process new memories. Studies need to explore the role of prior sleep for encoding, and to tease apart the contributions to infant memory of different types, features, and stages of sleep. We conclude that considering internal states, such as sleep, is necessary for developing a deeper understanding of early human memory.

The role of prior sleep for divergent thinking in infants

“…In research with adult populations, studies on the effects of prior sleep on cognition often involve sleep deprivation over significant periods of time (Yoo, Hu, Gujar, Jolesz, & Walker, 2007). Given that it is not possible for ethical and practical reasons to deprive infants of sleep (Seehagen et al, 2019), the current literature regarding infants, including the present study, does not rule out the possibility that timing of prior sleep does in fact shape infant cognition if the period of wakefulness is substantial enough. In one recent study (Seehagen, Herbert, & Zmyj, under review), a slightly different methodological approach did indeed point to effects of prior sleep on 6-month-old infants' cognition, specifically visual recognition of emotional faces.…”

State‐Dependent Memory in Infants

“…Hence, we use the term "state" broadly here to describe the internal context of the infants (cf. also Seehagen, Zmyj, & Herbert, 2019). In future studies the use of additional measures for the manipulation check (e.g., cortisol, mood ratings) and/or the manipulation of further internal cues (e.g., affect/mood, degree of satiation) will be desirable.…”

Infant Sleep as a Cornerstone for Cognitive Development

“…In this line of research, researchers typically assign infants to receive certain learning experiences at particular points during their naturally occurring sleep–wake patterns, for example, before an extended period of sleep or before an extended period of wakefulness (Seehagen et al, 2019). Memory for the target experience is assessed after a delay.…”

“…Specifically, with increasing age, infants encode new information faster (Barr et al, 1996), retain memories for longer periods of time (Herbert & Hayne, 2000), and become more flexible in using previously learned information in different situations (Hayne et al, 2000). Despite such marked developmental changes, at least some of the sleep effects observed in adult populations similarly apply to infant samples as well (Rasch & Born, 2013; Seehagen et al, 2019).…”

“…Conducting experimental research on sleep with infants involves working around practical and ethical issues (Seehagen et al, 2019). The most obvious challenges might be that sleep times can be difficult to predict and that systematic sleep restriction or deprivation for research purposes is difficult to achieve in smaller dosages (e.g., Berger et al, 2012), and out of the question to a greater extent.…”