Infant long-term memory for associations formed during mere exposure

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.

Here Today, Gone Tomorrow? Changes in 4-Month-Olds' Physiologic and Behavioral Responses Do Not Indicate Memory for a Social Stressor

Although much is known about early memory development, only a few studies have explored infants' memory of social stress. While these few studies suggest that infants can remember stressful interactions, limitations seen in both methodology and statistical analyses give pause. In the current study, 4-month-olds and their mothers participated in both stressful and non-stressful interactions over 2 days. On Day 1, memory group infants participated in the double Face-to-Face Still-Face (FFSF) paradigm and control group infants participated in typical play. Both groups experienced the double FFSF paradigm on Day 2. Memory group infants exhibited the standard SF response but no differences in infant cortisol on Day 1. Both infant groups exhibited the standard SF response on Day 2. However, infants in the memory group, who saw the FFSF paradigm for the second time, did not demonstrate changes in cortisol or behavior indicative of memory across the 2 days. There was also no relationship between changes in cortisol and behavior for both days. The findings question the use of salivary cortisol as a measure of social stress and suggest that, although 4-month-olds reacted to the Still-Face social stressor immediately, they did not remember the following day.

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.

Effortlessly strengthening infant memory: associative potentiation of new learning

We recently discovered that young infants learn a new association better in the presence of a prior association than when they learn it alone - a phenomenon we call associative potentiation. When 6-month-olds observed actions modeled on a puppet (remembered for 1 day) in the presence of a toy train they had learned to activate (remembered for 2 weeks), they remembered the demonstration for 2 weeks too. Currently, we examined the generality of associative potentiation. We found that when 6-month-olds learned the train task (remembered for 5 days) in the presence of two previously associated puppets (remembered for 4 weeks); they remembered the train task for 4 weeks too - more than five times longer. We conclude that associative potentiation is a general phenomenon: Cues for any stronger prior association will correspondingly increase the memory strength of any weaker new association that young infants learn in their presence, eliminating the need for repeated practice. We view associative potentiation as an adaptive mechanism that counteracts the rapid forgetting of younger infants by instantly increasing the strength of their new learning to a level characteristic of older infants. Neuromaturational models of infant memory cannot account for associative potentiation, but an ecological model does.