Selective imitation in 6-month-olds: the role of the social and physical context

Six-month-old infants\u27 learning of a new action from two different models (mother/stranger) was assessed in two settings (home/laboratory). In the laboratory, a significant number of infants learned the action from a stranger but not from their mother. In the infants\u27 homes, this pattern was reversed

Naps promote flexible memory retrieval in 12-month-old infants.

Flexibility in applying existing knowledge to similar cues is a corner stone of memory development in infants. Here, we examine the effect of sleep on the flexibility of memory retrieval using a deferred imitation paradigm. Forty-eight 12-month-old infants were randomly assigned to either a nap or a no-nap demonstration condition (scheduled around their natural daytime sleep schedule) or to a baseline control condition. In the demonstration conditions, infants watched an experimenter perform three target actions on a hand puppet. Immediately afterwards, infants were allowed to practice the target actions three times. In a test session 4-hr later, infants were given the opportunity to reproduce the actions with a novel hand puppet differing in color from the puppet used during the demonstration session. Only infants in the nap-condition performed significantly more target actions than infants in the baseline control condition. Furthermore, they were faster to carry out the first target action than infants in the no-nap condition. We conclude that sleep had a facilitative effect on infants' flexibility of memory retrieval

Timely sleep facilitates declarative memory consolidation in infants

Human infants devote the majority of their time to sleeping. However, very little is known about the role of sleep in early memory processing. Here we test 6- and 12-mo-old infants’ declarative memory for novel actions after a 4-h [Experiment (Exp.) 1] and 24-h delay (Exp. 2). Infants in a nap condition took an extended nap (≥30 min) within 4 h after learning, whereas infants in a no-nap condition did not. A comparison with age-matched control groups revealed that after both delays, only infants who had napped after learning remembered the target actions at the test. Additionally, after the 24-h delay, memory performance of infants in the nap condition was significantly higher than that of infants in the no-nap condition. This is the first experimental evidence to our knowledge for an enhancing role of sleep in the consolidation of declarative memories in the first year of life

The role of demonstrator familiarity and language cues on infant imitation from television

An imitation procedure was used to investigate the impact of demonstrator familiarity and language cues on infant learning from television. Eighteen-month-old infants watched two pre-recorded videos showing an adult demonstrating a sequence of actions with two sets of stimuli. Infants' familiarity with the demonstrator and the language used during the demonstration varied as a function of experimental condition. Immediately after watching each video, infants' ability to reproduce the target actions was assessed. A highly familiar demonstrator did not enhance infants' performance. However, the addition of a narrative, developed from mothers' naturalistic description of the event, facilitated learning from an unfamiliar demonstrator. We propose that the differential effect of demonstrator familiarity and language cues may reflect the infants' ability to distinguish between important and less important aspects in a learning situation. (C) 2010 Elsevier Inc. All rights reserved

Infant imitation from televised peer and adult models

Developmental changes in learning from peers and adults during the second year of life were assessed using an imitation paradigm. Independent groups of 15- and 24-month-old infants watched a prerecorded video of an unfamiliar child or adult model demonstrating a series of actions with objects. When learning was assessed immediately, 15-month-old infants imitated the target actions from the adult, but not the peer whereas 24-month-old infants imitated the target actions from both models. When infants\u27 retention was assessed after a 10-min delay, only 24-month-old infants who had observed the peer model exhibited imitation. Across both ages, there was a significant positive correlation between the number of actions imitated from the peer and the length of regular peer exposure reported by caregivers. Length of peer exposure was not related to imitation from the adult model. Taken together, these findings indicate that a peer-model advantage develops as a function of age and experience during the second year of life

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

Research with adults has shown that a person\u27s 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

Gist extraction and sleep in 12-month-old infants

Gist extraction is the process of excerpting shared features from a pool of new items. The present study examined sleep and the consolidation of gist in 12-month-old infants using a deferred imitation paradigm. Sixty infants were randomly assigned to a nap, a no-nap or a baseline control condition. In the nap and no-nap conditions, infants watched demonstrations of the same target actions on three different hand puppets that shared some features. During a 4-h delay, infants in the nap condition took a naturally scheduled nap while infants in the no-nap condition naturally stayed awake. Afterwards, infants were exposed to a novel forth hand puppet that combined some of the features from the previously encountered puppets. Only those infants who took a nap after learning produced a significantly higher number of target actions than infants in the baseline control condition who had not seen any demonstrations of target actions. Infants in the nap condition also produced significantly more target actions than infants in the no-nap condition. Sleep appears to support the storage of gist, which aids infants in applying recently acquired knowledge to novel circumstances

The relationship between prior night\u27s sleep and measures of infant imitation

We examined whether sleep quality during the night and naps during the day preceding a learning event are related to memory encoding in human infants. Twenty-four 6- and twenty-four 12-month-old infants\u27 natural sleeping behavior was monitored for 24 hr using actigraphy. After the recording period, encoding was assessed using an imitation paradigm. In an initial baseline phase, infants were allowed to interact with the stimulus to assess spontaneous production of any target actions. Infants then watched an experimenter demonstrate a sequence of three target actions and were immediately given the opportunity to reproduce the demonstrated target actions to assess memory encoding. Analyses revealed significant correlations between nighttime sleep quality variables (sleep efficiency, sleep fragmentation) and immediate imitation in 6-month-olds, but not in 12-month-olds. High sleep quality in the preceding night was thus positively associated with next day\u27s memory encoding in 6-month-old infant