Age-related changes in spreading activation during infancy

Prior sleep timing and visual recognition of emotional faces in 6-month-old infants

Face recognition is an important mnemonic ability for infants when navigating the social world. While age-related changes in face processing abilities are relatively well documented, less is known about short-term intra-individual fluctuations in this ability. Given that sleep deprivation in adults leads to impairments in information processing, we assessed the role of prior sleep on 6-month-old infants' (N = 17) visual recognition of faces showing three emotional expressions (neutral, sad, angry). Visual recognition was inferred by assessing novelty preferences for unfamiliar relative to familiarized faces in a visual recognition memory paradigm. In a within-subject design, infants participated once after they had recently woken up from a nap (nap condition) and once after they had been awake for an extended period of time (awake condition). Infants failed to show visual recognition for the neutral faces in either condition. Infants showed recognition for the sad and angry faces when tested in the awake condition, but not in the nap condition. This suggests that timing of prior sleep shapes how effectively infants process emotionally relevant information in their environment.

State-Dependent Memory in Infants

Why do infants remember some things and not others? Human infants frequently cycle through different states such as calm attentiveness, wakeful activity, and crying. Given that cognitive processes do not occur in isolation, such fluctuations in internal state might influence memory processing. In the present experiment, declarative memory in 9-month-old infants (N = 96) was heavily state dependent. Infants exhibited excellent retention of a deferred imitation task after a 15-min delay if their state at encoding was identical to their state at retrieval (e.g., calm). Infants failed to exhibit retention if their state at encoding was different from their state at retrieval (e.g., calm vs. animated). Infant memory processing depends on internal cues.

Associative binding in early childhood: Evidence from a preferential looking paradigm

Relational memory processes are responsible for forming representations that bind together the co-occurring elements of an experience. These processes provide a foundation of episodic memory, the capacity to remember specific events about one's past. In the present research, we used a visual comparison paradigm to determine whether toddlers can form memories for the relation between co-occurring items. In Experiment 1, 66 2-year-olds viewed pairs of cartoon faces (AB; CD) and did not show a significant novelty preference for the violated associations (i.e., did not look longer at AD rearranged pair than old AB pair when exposed to AD-AB). However, toddlers looked longest at the individual face (i.e., D) violating a studied pair, which appeared to be supported by visual preference for centrally located stimuli. In Experiment 2, 46 2-year-olds participated in a similar procedure, but faces violating the pair during test were located to the periphery (e.g., AB-AC). Under these conditions, toddlers looked longer at recombined pair AC. Overall, our results show that toddlers show some ability to make item-item associations but may need to overcome preferential looking biases to demonstrate this capacity. Furthermore, looking behaviors beyond overall novelty preference may be informative even when overall novelty preference is not found.

Beyond the Bayley: Neurocognitive Assessments of Development During Infancy and Toddlerhood

The use of global, standardized instruments is conventional among clinicians and researchers interested in assessing neurocognitive development. Exclusively relying on these tests for evaluating effects may underestimate or miss specific effects on early cognition. The goal of this review is to identify alternative measures for possible inclusion in future clinical trials and interventions evaluating early neurocognitive development. The domains included for consideration are attention, memory, executive function, language, and socioemotional development. Although domain-based tests are limited, as psychometric properties have not yet been well-established, this review includes tasks and paradigms that have been reliably used across various developmental psychology laboratories.

Memory by association: Integrating memories prolongs retention by two-year-olds

Recalling one memory often leads to the recollection of other memories that share overlapping features. This phenomenon, spreading activation, was originally documented in studies conducted with verbal adults, and more recently, it has been demonstrated with preverbal infants. Here, we examine the effect of spreading activation on long-term retention by 2-year-olds. Participants were tested in the Visual Recognition Memory (VRM) paradigm and the deferred imitation paradigm. Typically, infants of this age exhibit retention in the VRM paradigm for 24h, while they exhibit retention in the deferred imitation paradigm for at least 8 weeks. In the present experiment, we paired these tasks together during original encoding and tested infants after an 8-week delay. Two-year-olds exhibited retention in both tasks. That is, when these two tasks initially occurred together - one task that is extremely memorable and one that is not - retrieving the memory of the more memorable task cued retrieval of the less memorable task, extending its longevity.

Occlusions at event boundaries during encoding have a negative effect on infant memory

The present study investigated the importance of Event Boundaries for 16- and 20-month-olds' (n=80) memory for cartoons. The infants watched one out of two cartoons with ellipses inserted covering the screen for 3s either at Event Boundaries or at Non-Boundaries. After a two-week delay both cartoons (one familiar and one novel) were presented simultaneously without ellipses while eye-tracking the infants. According to recent evidence a familiarity preference was expected. However, following Event Segmentation Theory ellipses at Event Boundaries were expected to cause greater disturbance of the encoding and hence a weaker memory trace evidenced by reduced familiarity preference, relative to ellipses at Non-Boundaries. The results suggest that overall this was the case, documenting the importance of Boundaries for infant memory. Furthermore, planned analyses revealed that whereas the same pattern was found when looking at the 20-month-old infants, no significant difference was found between the two conditions in the youngest age-group.

Socioeconomic disparities in neurocognitive development in the first two years of life

Socioeconomic status (SES) is strongly associated with cognition and achievement. Socioeconomic disparities in language and memory skills have been reported from elementary school through adolescence. Less is known about the extent to which such disparities emerge in infancy. Here, 179 infants from socioeconomically diverse families were recruited. Using a cohort-sequential design, 90 infants were followed at 9 and 15 months, and 89 were followed at 15 and 21 months. SES disparities in developmental trajectories of language and memory were present such that, at 21 months of age, children of highly educated parents scored approximately .8 standard deviations higher in both language and memory than children of less educated parents. The home language and literacy environment and parental warmth partially accounted for disparities in language, but not memory development.

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.