Effects of priming duration on retention over the first 1 1/2 years of life

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.

All the Right Noises: Background Variability Helps Early Word Learning

Variability is prevalent in early language acquisition, but, whether it supports or hinders learning is unclear; while target variability has been shown to facilitate word learning, variability in competitor items has been shown to make the task harder. Here, we tested whether background variability could boost learning in a referent selection task. Two groups of 2-year-old children saw arrays of one novel and two known objects on a screen, and they heard a novel or known label. Stimuli were identical across conditions, with the exception that in the constant color condition objects appeared on a uniform white background, and in the variable color condition backgrounds were different, uniform colors. At test, only children in the variable condition showed evidence of retaining label-object associations. These data support findings from the adult memory literature, which suggest that variability supports learning by decontextualizing representations. We argue that these data are consistent with dynamic systems accounts of learning in which low-level entropy adds sufficient noise to the developmental system to precipitate a change in behavior.

Carolyn Rovee-Collier's legacy to applied psychology, intervention, and public policy

In this article, we reflect upon Carolyn Rovee-Collier's pioneering research on learning and memory in infants, especially that using the mobile conjugate reinforcement task, for our understanding of (a) cognitive development in infants born prematurely and those with Down's syndrome and (b) her prediction that infants' performance in the mobile conjugate reinforcement and similar operant tasks would predict later intellectual functioning. We then examine the implications of her research on time windows (the integration of new information into a memory) and memory reactivation (the retrieval of a forgotten memory as a result of the re-exposure to a component of the original learning experience) for early intervention programs and clinicians treating victims of early trauma. We conclude with a discussion of the value of Rovee-Collier's work for the growing field of infant/toddler science and how this science has informed public policy and program development.

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.

When do infants begin recognizing familiar words in sentences?

Previous studies have shown that by 11 but not by 10 months infants recognize words that have become familiar from everyday life independently of the experimental setting. This study explored the ability of 10-, 11-, and 12-month-old infants to recognize familiar words in sentential context, without experimental training. The headturn preference procedure was used to contrast passages containing words likely to be familiar to the infants with passages containing words unlikely to have been previously heard. Two stimulus words were inserted near the beginning and end of each of a set of simple sentence frames. The ability to recognize the familiar words within sentences emerged only at 12 months of age. The contrast between segmentation abilities as they emerge as a result of everyday exposure to language, as assessed here, and those abilities as measured in studies in which words are experimentally trained is discussed in terms of memory-based mechanisms.

Multiple memory systems are unnecessary to account for infant memory development: an ecological model

How the memory of adults evolves from the memory abilities of infants is a central problem in cognitive development. The popular solution holds that the multiple memory systems of adults mature at different rates during infancy. The early-maturing system (implicit or nondeclarative memory) functions automatically from birth, whereas the late-maturing system (explicit or declarative memory) functions intentionally, with awareness, from late in the first year. Data are presented from research on deferred imitation, sensory preconditioning, potentiation, and context for which this solution cannot account and present an alternative model that eschews the need for multiple memory systems. The ecological model of infant memory development (N. E. Spear, 1984) holds that members of all species are perfectly adapted to their niche at each point in ontogeny and exhibit effective, evolutionarily selected solutions to whatever challenges each new niche poses. Because adults and infants occupy different niches, what they perceive, learn, and remember about the same event differs, but their raw capacity to learn and remember does not.

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.

Age-related changes in memory reactivation by 1- and 2-year-old human infants

In three experiments, we examined the effect of a single reactivation treatment on retention by 1- and 2-year-old human infants who were tested in the visual recognition memory (VRM) paradigm. In all experiments, infants were familiarized with a visual stimulus and were tested after a delay. In the absence of a reactivation treatment, infants of both ages exhibited forgetting but exposure to a reactivation treatment alleviated forgetting after the same delay. When the duration of the original familiarization period was only 10 s, the minimum duration of an effective reminder treatment was 1 s for 2-year-olds, but was 5 s for 1-year-olds. When the duration of the original familiarization period was increased to 30 s, however, a 1-s reminder also alleviated forgetting by 1-year-olds.

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.