Napping and toddlers’ memory for fast-mapped words

Abstract

When toddlers hear a novel word, they quickly and independently link it with a novel object rather than known-name objects. However, they are less proficient in retaining multiple novel words. Sleep and even short naps can enhance declarative memory in adults and children and this study investigates the effect of napping on children's memory for novel words. Forty two-and-a-half-year-old children were presented with referent selection trials for four novel nouns. Children's retention of the words was tested immediately after referent selection, four hours later in the afternoon, and the following morning. Half of the toddlers napped prior to the afternoon retention test. Amongst the toddlers who napped, retention scores remained steady four hours after exposure and the following morning. In contrast, for the wake group, there was a steady decline in retention scores by the following morning and significantly lower retention scores compared to the nap group. Napping following exposure to novel word-object associations could help in maintaining memories and limiting decay. Nap duration was also associated with better retention scores, but there were no effects of sleep quality, habitual napping, or sleepiness. The findings have implications for the role of napping in children's language acquisition.

Adult Fast-Mapping Memory Research Is Based on a Misinterpretation of Developmental-Word-Learning Data

“…Indeed, it is conceivable that functional development of the hippocampus supports the emergence of long-term retention. That would be consistent with the sensitivity of such retention to whether children nap immediately following learning (Axelsson et al, 2018), given the role that sleep has been proposed to play in hippocampus-mediated memory consolidation (e.g., Davis & Gaskell, 2009; Gais & Born, 2004; cf. Himmer et al, 2017).…”

“…Indeed, Axelsson and Horst (2013) found that 2-year-olds failed to show even immediate retention of novel words following fast mapping of more than one novel word. Recent data, however, suggest that 2.5-year-olds can show some retention 24 hr after fast mapping four novel words, but only if they nap immediately after learning (Axelsson, Swinton, Winiger, & Horst, 2018).…”

Where’s the Advantage? Mutual Exclusivity Promotes Children’s Initial Mapping, but Not Long-Term Memory, for Words Compared to Other Strategies

“…First, this work demonstrates that MEB does not yield stronger retention for word mappings after a delay. Although there are a small number of studies with young children that have examined MEB after the moment of learning (e.g., Horst and Samuelson, 2008 ; Axelsson et al, 2018 ), most of these studies demonstrate no retention after a brief delay (i.e., chance performance) without additional memory supports. In contrast, this work demonstrates that, even in situations when children are indeed able to retain information at the delayed test, use of MEB does not promote long-term retention of words relative to other alternative, unspecified disambiguation strategies.…”

“…Although there have been many studies conducted on children’s use of MEB, there is a striking limitation of the MEB literature: assessments of word mapping are most often administered at an immediate test, directly following the learning event (e.g., Merriman et al, 1989 ; Au and Glusman, 1990 ; but see Horst and Samuelson, 2008 ; Axelsson et al, 2018 ). That is, these studies examine children’s mapping, but not retention, of new words learned via MEB.…”

The Role of Sleep in Retention of New Words in Habitually and Non-Habitually Napping Children

“…Previous work has demonstrated that daytime sleep contributes to memory consolidation-an important consideration for vocabulary acquisition-in infants [7][8][9][10][11][12] and children [13][14][15][16][17]. An additional consideration in the relationship between daytime sleep and memory in children is that daytime sleep patterns across a 24-h period change substantially across early development and naps are eventually phased out.…”