Retrieval Protracts Deferred Imitation by 6-Month-Olds

Touchscreens for Whom? Working Memory and Age Moderate the Impact of Contingency on Toddlers' Transfer From Video

Toddlers exhibit poor transfer between video and real-world contexts. Contingently responsive video such as that found in touchscreen apps appears to assist transfer for some toddlers but not others. This study investigated the extent to which toddlers' working memory moderates the impact of contingency on toddler's transfer of learning from video. Toddlers (24–36 months; N = 134) watched a hiding event on either (a) contingent video that advanced only after touch input or (b) non-contingent video that proceeded automatically. Toddlers then searched for a corresponding object on a felt board. Additionally, toddlers' working memory (WM) was assessed. Findings indicate WM and age moderated the impact of contingency on transfer: Contingency decreased transfer in younger children while increasing transfer among older children. However, this was only true for children with relatively low WM. Contingency had little impact on transfer among children with relatively high WM, regardless of age. Results from this study suggest that WM is one specific moderator that predicts whether toddlers are likely to learn from contingent vs. non-contingent video, yet WM does not operate in isolation. Together, these findings underscore the importance of considering multiple child characteristics when identifying the optimal conditions for toddlers' learning from symbolic media.

The Ontogeny of Hippocampus-Dependent Memories

The formation of memories that contain information about the specific time and place of acquisition, which are commonly referred to as "autobiographical" or "episodic" memories, critically relies on the hippocampus and on a series of interconnected structures located in the medial temporal lobe of the mammalian brain. The observation that adults retain very few of these memories from the first years of their life has fueled a long-standing debate on whether infants can make the types of memories that in adults are processed by the hippocampus-dependent memory system, and whether the hippocampus is involved in learning and memory processes early in life. Recent evidence shows that, even at a time when its circuitry is not yet mature, the infant hippocampus is able to produce long-lasting memories. However, the ability to acquire and store such memories relies on molecular pathways and network-based activity dynamics different from the adult system, which mature with age. The mechanisms underlying the formation of hippocampus-dependent memories during infancy, and the role that experience exerts in promoting the maturation of the hippocampus-dependent memory system, remain to be understood. In this review, we discuss recent advances in our understanding of the ontogeny and the biological correlates of hippocampus-dependent memories.

Imitation in Angelman syndrome: the role of social engagement

Individuals with Angelman syndrome (AS) are characterized by severe cognitive impairments alongside an enhanced drive for social engagement. As knowledge on imitation skills in this population is limited, we conducted the first controlled study of imitation in AS. We examined how 23 individuals with AS and 21 typically developing young children with similar mental age imitated novel actions in response to socially or non-socially engaging models, and in response to video-recorded versus live demonstrations of novel actions. Individuals with AS imitated as frequently and as accurately as typical young children in response to live demonstrations; but they imitated less frequently and less accurately in response to video-recorded demonstrations. Further, imitation was modulated by whether the demonstrator was socially engaging or emotionally neutral in the AS group, while this modulation was not present in the comparison group. Individuals with higher mental age imitated more frequently and more accurately across groups. Imitation performance in AS appears to be more modulated by the social context compared to typical infants and young children with similar mental age, possibly reflecting an enhanced drive for social engagement. A socially engaging instructional style might facilitate imitative learning in this population.

Ontogenesis of learning and memory: Biopsychosocial and dynamical systems perspectives

In this article, we review recent empirical and theoretical work on infant memory development, highlighting future directions for the field. We consider the state of the field since Carolyn Rovee-Collier's call for developmental scientists to "shift the focus from what to why," emphasizing the function of infant behavior and the value of integrating fractionized, highly specialized subfields. We discuss functional approaches of early learning and memory, including ecological models of memory development and relevant empirical work in human and non-human organisms. Ontogenetic changes in learning and memory occur in developing biological systems, which are embedded in broader socio-cultural contexts with shifting ecological demands that are in part determined by the infants themselves. We incorporate biopsychosocial and dynamical systems perspectives as we analyze the state of the field's integration of multiple areas of specialization to provide more holistic understanding of the contributing factors and underlying mechanisms of the development of memory.

Anticipatory eye movements and long-term memory in early infancy

Advances in our understanding of long-term memory in early infancy have been made possible by studies that have used the Rovee-Collier's mobile conjugate reinforcement paradigm and its variants. One function that has been attributed to long-term memory is the formation of expectations (Rovee-Collier & Hayne, 1987); consequently, a long-term memory representation should be established during expectation formation. To examine this prediction and potentially open the door on a new paradigm for exploring infants' long-term memory, using the Visual Expectation Paradigm (Haith, Hazan, & Goodman, 1988), 3-month-old infants were trained to form an expectation for predictable color and spatial information of picture events and emit anticipatory eye movements to those events. One day later, infants' anticipatory eye movements decreased in number relative to the end of training when the predictable colors were changed but not when the spatial location of the predictable color events was changed. These findings confirm that information encoded during expectation formation are stored in long-term memory, as hypothesized by Rovee-Collier and colleagues. Further, this research suggests that eye movements are potentially viable measures of long-term memory in infancy, providing confirmatory evidence for early mnemonic processes.

Transitions in the temporal parameters of sensory preconditioning during infancy

Sensory preconditioning (SPC) is a form of latent learning in which preexposure to co-occurring neutral stimuli (S1 -S2 ) permits subsequent learning to be transferred from one stimulus (S1 ) to the other (S2 ). We examined whether human infants exhibit developmental transitions in the temporal parameters of SPC by manipulating the preexposure regimen. Infants received simultaneous or sequential preexposure to puppets S1 and S2 (Days 1-2); saw target actions modeled on S1 (Day 3); and were tested for deferred imitation with S2 (Day 4). Although 6-, 9-, and 12-month-olds associated the puppets, there was a shift in the effective regimen from simultaneous to sequential preexposure-similar to prior findings with rat pups (Experiment 1). Experiment 2 revealed that human infants potentially exhibit another transition in SPC at 15 and 18 months of age. We consider the roles of ontogenetic shifts in infants' ecological niche, selective attention, and unitization in developmental transitions in SPC.

Deconstructing the reactivation of imitation in young infants

Reactivation is an automatic, perceptual process in which exposure to components of a forgotten event alleviates forgetting. Most research on infant memory reactivation has used conditioning paradigms. We used the puppet imitation task to systematically examine which stimuli could retrieve 6-month-olds' forgotten memory of the modeled actions. Infants watched an adult model a sequence of actions on a puppet, imitated the actions, and were exposed to reactivation cues 24 hr before a 7-day (Experiment 1) or 14-day (Experiment 2) retention test. Exposure to any component of the original event reactivated the memory during the 7-day test, but two of the same components failed to alleviate forgetting during the 14-day test. Increasing the number of retrieval cues facilitated 14-day test performance. These findings reveal that the principles of reactivation are the same for conditioning and imitation paradigms: The necessary and sufficient conditions for memory reactivation are directly related to memory accessibility.

The relation between contingency preference and imitation in 6–8-month-old infants

Detecting self-generated actions and imitating other-generated actions are important abilities in order to interact with others. The relationship between these domains was investigated in 6–8-month-old infants. In a contingency-preference task, infants observed their own legs on a real-time and a delayed video display. In an imitation task, the experimenter demonstrated a three-step action directed at a puppet mouse. The Cognitive Scale of the Bayley Scales of Infant and Toddler Development was administered in order to control for the infants’ cognitive developmental status. A negative correlation was found between the proportion of time spent looking at the delayed display in the contingency-preference task and the imitation score in the imitation task. This indicates that the lower the infants’ preference for the delayed video image, the more likely they were to imitate. The correlation between contingency preference and imitation remained even after controlling for cognitive developmental status. Thus, a basic interest in high contingency might underlie the preference for observing self-generated actions and imitating other-generated actions.

Learning to remember: the early ontogeny of episodic memory

Over the past 60 years the neural correlates of human episodic memory have been the focus of intense neuroscientific scrutiny. By contrast, neuroscience has paid substantially less attention to understanding the emergence of this neurocognitive system. In this review we consider how the study of memory development has evolved. In doing so, we concentrate primarily on the first postnatal year because it is within this time window that the most dramatic shifts in scientific opinion have occurred. Moreover, this time frame includes the critical age (∼9 months) at which human infants purportedly first begin to demonstrate rudimentary hippocampal-dependent memory. We review the evidence for and against this assertion, note the lack of direct neurocognitive data speaking to this issue, and question how demonstrations of exuberant relational learning and memory in infants as young as 3-months old can be accommodated within extant models. Finally, we discuss whether current impasses in the infant memory literature could be leveraged by making greater use of neuroimaging techniques, such as magnetic resonance imaging (MRI), which have been deployed so successfully in adults.

The effect of a final exam on long-term retention

Testing on a final exam in a college course improved long-term retention over material that had not been tested on the final. Students from an upper level psychology course took a long-term retention test, four to five months after the end of the course. For half of the items, a related question had been on the final. For the remaining half, a related question had appeared on an earlier exam, but not the final. On the long-term retention test, percent correct was 79% when a related question had appeared on the final and 67% when a related question had not appeared on the final. These results have both theoretical and practical implications.

Age-related changes in spreading activation during infancy

The concept of spreading activation describes how retrieval of one memory cues retrieval of other memories that are associated with it. This study explored spreading activation in 6-, 12-, and 18-month-old infants. Infants (n = 144) learned two tasks within the same experimental session; one task, deferred imitation (DI), is typically remembered longer than the other task, visual recognition memory (VRM). At all ages, retrieval of the DI memory facilitated retrieval of the VRM memory, but the conditions under which this spreading activation occurred changed as a function of age. The implications of these findings are discussed in relation to the development of mnemonic networks during infancy and the value of studying infants for our understanding of memory more generally.

Long-term transfer of learning from books and video during toddlerhood

Television viewing and picture book reading are prevalent activities during toddlerhood, and research has shown that toddlers can imitate from both books and videos after short delays. This is the first study to directly compare toddlers' long-term retention rates for target actions learned from a video or book. Toddlers (N=158) at 18- and 24-months of age saw an experimenter demonstrating how to make a novel three-step toy rattle via a prerecorded video or a picture book. The toddlers' imitation of the target actions was tested after a specific delay (e.g., 2, 4 weeks), and their performance was compared with that of age-matched controls who did not see a demonstration. The 18-month-olds retained the target actions for 2 weeks, exhibiting forgetting at 4 weeks, whereas the 24-month-olds retained the information for up to 4 weeks, exhibiting forgetting at 8 weeks. Retention rates for books and videos did not differ at either age. These findings demonstrate very impressive retention from a brief two-dimensional media demonstration, and they contribute to our overall understanding of long-term memory processes during infancy.

Effects of viewing ordered pictorial reminders on long-term memory in the first year of life

Previous research has shown that reminders can be effective for extending and enhancing a variety of kinds of memory in infants. We investigated the effects of viewing pictorial representations of actions that were included in imitation events used to measure long-term memory in young infants. Infants who saw the pictures of actions displayed in the order in which they comprised events showed evidence of memory for the events. Infants who saw the actions presented randomly did not. These results suggest that pictures presented during the consolidation and storage phase of memory formation can be effective reminders of events for young infants.

Potentiation in young infants: the origin of the prior knowledge effect?

In two experiments with 6-month-old infants, we found that prior learning of an operant task (remembered for 2 weeks) mediated new learning of a modeling event (remembered for only 1 day) and increased its recall. Infants first learned to associate lever pressing with moving a toy train housed in a large box. One or 2 weeks later, three target actions were modeled on a hand puppet while the train box (a retrieval cue) was in view. Merely retrieving the train memory strengthened it, and simultaneously pairing its retrieved memory with the modeled actions potentiated their learning and recall. When paired 1 week later, deferred imitation increased from 1 day to 4 weeks; when paired 2 weeks later, it increased from 1 day to 6 weeks. The striking parallels between potentiated learning in infants and the prior knowledge effect in adults suggests that the prior knowledge effect originates in early infancy.

Infant long-term memory for associations formed during mere exposure

We previously found that young infants spontaneously associate stimuli that they merely see together. Using a sensory preconditioning paradigm with 6- and 9-month-olds, we asked how long such associations remain latent before being forgotten and what exposure conditions affect their persistence. Groups were preexposed to two puppets for 1h/day for 2 days, 1h on 1 day, or 1h on 1 day in two sessions; 1-27 days later, target actions were modeled on one puppet, and infants were tested with the other puppet 1 day later. The longest delay after which infants imitated the actions on the other puppet defined how long they remembered the association. The data revealed that the preexposure regimen determined retention. Regardless of exposure time, both ages remembered the association longer after two sessions, and younger infants remembered longer than older infants--for 4 weeks--after two 30-min sessions on 1 day.

Transfer of learning between 2D and 3D sources during infancy: Informing theory and practice

The ability to transfer learning across contexts is an adaptive skill that develops rapidly during early childhood. Learning from television is a specific instance of transfer of learning between a 2-Dimensional (2D) representation and a 3-Dimensional (3D) object. Understanding the conditions under which young children might accomplish this particular kind of transfer is important because by 2 years of age 90% of US children are viewing television on a daily basis. Recent research shows that children can imitate actions presented on television using the corresponding real-world objects, but this same research also shows that children learn less from television than they do from live demonstrations until they are at least 3 years old; termed the video deficit effect. At present, there is no coherent theory to account for the video deficit effect; how learning is disrupted by this change in context is poorly understood. The aims of the present review are (1) to review the conditions under which children transfer learning between 2D images and 3D objects during early childhood, and (2) to integrate developmental theories of memory processing into the transfer of learning from media literature using Hayne's (2004) developmental representational flexibility account. The review will conclude that studies on the transfer of learning between 2D and 3D sources have important theoretical implications for general developmental theories of cognitive development, and in particular the development of a flexible representational system, as well as policy implications for early education regarding the potential use and limitations of media as effective teaching tools during early childhood.

The influence of electronic sound effects on learning from televised and live models

Infants rapidly accrue information via imitation from multiple sources, including television and electronic toys. In two experiments, we examined whether adding sound effects to video or live demonstrations would influence imitation by 6-, 12-, and 18-month-olds. In Experiment 1, we added matching and mismatching sound effects to target actions presented by a televised model. We found that 6-month-olds reproduced the target actions regardless of whether the sound effects were matched or mismatched, whereas 12- and 18-month-olds reproduced the actions only when the sound effects were matched. In Experiment 2, we added matching sound effects to target actions presented by a live model. The addition of sound effects disrupted imitation performance by 6-, 12-, and 18-month-olds. Overall, imitation provides a clear behavioral measure of rapid changes in learning from television and electronic toys during infancy. These findings have practical implications for producers and parents regarding learning in the digital age and theoretical implications regarding the development of integrated action-perception representational systems.

The specificity of priming effects over the first year of life

Despite its significance for the enduring effect of early experience, the specificity of priming on infants' forgotten memories is unknown. This study determined the impact of cue and context changes on the initial priming and retrieval of the reactivated memory over the first postnatal year. Infants were operantly trained with a distinctive cue in a particular context. After forgetting, they were primed and tested for renewed retention with combinations of old and new cues and contexts. Priming was hyperspecific to the original cue and original context at all but 12 months, when the memory was reactivated in a novel context. At 9-12 months, the reactivated memory generalized to a novel cue or context. At younger ages, the reactivated memory generalized only after a very brief prime. These findings indicate that priming in early infancy is initially conservative, buffering against recovering memories in contexts that might no longer be appropriate.

The effect of repetition on imitation from television during infancy

Although television exposure levels during infancy are high, the impact of such exposure on learning is relatively unknown. Initial studies have shown that infants imitate significantly fewer target actions from a televised demonstration than they imitate from a live demonstration. It was hypothesized that increasing the duration of exposure to the videotaped demonstration would increase learning from television. Independent groups of 12- to 21-month-olds were exposed to live or videotaped demonstrations of target actions, and imitation of the target actions was measured 24 hr later. The video segment duration was twice that of the live presentation. Doubling exposure increased levels of imitation performance in the video groups to that of the live groups, and both groups exceeded baseline performance. These results are consistent with the perceptual encoding impoverishment theory, and we conclude that repeated exposure enhances encoding of the target actions from a 2D television source.

Copying actions and copying outcomes: social learning through the second year

The present work documents how the logic of a model's demonstration and the communicative cues that the model provides interact with age to influence how children engage in social learning. Children at ages 12, 18, and 24 months (n=204) watched a model open a series of boxes. Twelve-month-old subjects only copied the specific actions of the model when they were given a logical reason to do so--otherwise, they focused on reproducing the outcome of the demonstrated actions. Eighteen-month-old subjects focused on copying the outcome when the model was aloof. When the model acted socially, the subjects were as likely to focus on copying actions as outcomes, irrespective of the apparent logic of the model's behavior. Finally, 24-month-old subjects predominantly focused on copying the model's specific actions. However, they were less likely to produce the modeled outcome when the model acted non-socially.

Repeated priming increases memory accessibility in infants

In previous research on priming (reactivation) with 3-month-olds, two primes recovered a forgotten memory faster than one, suggesting that prior priming had increased the accessibility of the forgotten memory. Exploiting the fact that the minimum duration of a prime indexes the accessibility of the forgotten memory, we currently examined whether prior priming also reduces the minimum effective prime duration. In three experiments, 60 3-month-olds learned an operant task, forgot it, and then were exposed to successive primes either 1 day and 1 week after forgetting (Experiment 1) or 1 and 2 weeks after forgetting (Experiment 2). In both cases, prior priming reduced the minimum duration of the second prime, a result that was independent of the duration of the first prime (Experiment 3). These findings confirm that priming increases the accessibility of a latent memory and raise the possibility that repeated priming underlies the extended memorability of persons and events that infants encounter sporadically.

Memory reactivation in the second year of life

Memory reactivation has not been systematically studied with infants older than 1 year. Currently, three experiments examined the effects of a reactivation treatment (priming) on retention throughout the second postnatal year. Fifteen- and 18-month-olds learned an operant train task, forgot it, received a 2-min or 10-s prime, and later were tested for retention. Although the longer prime was effective for 15-month-olds, 18-month-olds required the shorter prime (Experiment 1). The memory was reactivated after delays two (18 months) and three (15 months) times longer than infants originally remembered it (Experiment 2). The reactivated memory was forgotten as fast as the original memory after the 2-min prime and twice as fast after the 10-s prime (Experiment 3). The fact that reactivation changes quantitatively but not qualitatively throughout infancy suggests that the same mechanism mediates it at all ages. These findings have major implications for the impact of early experience on cognitive development.