Learning to understand others’ emotions from an early age is crucial for long-term social-cognitive development. However, much remains unknown regarding potential mechanisms behind the development of early emotion understanding. Some theoretical work has proposed that language may facilitate the development of emotion understanding (e.g., Barrett, 2017), while other theoretical work argues that language should not be crucial for such development (e.g., Ekman & Cordaro, 2011). Thus, to better understand how children learn to understand emotions, what may explain some of the large individual differences observed in early emotion understanding, and what theoretical perspective may best explain early emotion understanding development, it is important to further examine the role of language in early emotion understanding development. The present studies use a novel approach to examining the relation between language and emotion understanding across early development using 1) Eye tracking, 2) Corpus analysis, and 3) Live action assessment of emotion category learning methodologies. Study 1 examined whether infant performance on a completely non-linguistic emotion categorization task related to infant language abilities. Participants were 50 infants between 15- and 18-months of age who completed the emotion categorization task using an eye tracker and whose parents provided the infants’ vocabularies. Results from this study revealed that non-linguistic emotion categorization related to vocabulary size for girls, but not for boys, providing some evidence that language may begin to relate to early emotion categorization abilities in infancy. Study 2 investigated young children’s natural language environments and how this environment relates to children’s propensity to talk about emotion words. Nearly 2,000 transcripts of natural interactions between mothers and their 15- to 47-month-old child were drawn from the CHILDES (MacWhinney, 2000) database. Findings from this study revealed that child use of emotion language was significantly predicted by their age and their mother’s use of emotion language, but not by the child or mother’s general language complexity. These results suggest that exposure to emotion language, but not necessarily general language, may be important for children’s developing ability to talk about and understand emotions. Study 3 evaluated whether exposure to specific emotion words would causally influence children’s ability to learn about new, complex emotions. Across two experiments, 72 3-year-old children took part in a pre-test post-test emotion category learning assessment where they were tasked with identifying which face best matched how a character would feel in a scenario. Between pre-test and post-test, children saw a face paired with a scenario and either heard an explicit emotion label, a vague emotion label, or irrelevant information. Results revealed that children learned the face-scenario associations better when given an explicit emotion label versus irrelevant information (Study 1), but vague emotion labels did not provide any advantage over irrelevant information (Study 2). Taken together, these results suggest that explicit emotion labels may be particularly important for helping young children learn about emotions. In sum, these three studies provide some evidence that language may be important for the development of early emotion understanding. However, the strength of this evidence varied by study, suggesting that other factors such as the particular methodology being used, child age, and use of emotion language versus general language, may play important roles in understanding this relation. Altogether, these results present evidence that may be useful for more comprehensively understanding the potential mechanistic role of language in the early development of emotion understanding.

The goal of this dissertation was to examine the scope and development of early visual short-term memory (VSTM) abilities in 6–12-month-old infants. Study 1 investigated individual- and age-related differences across three unique VSTM tasks by examining the effect of increased delay on memory performance. Results suggest longer-term memory processes are quantifiable utilizing 500-1250 ms delays by 8 months with the Change Detection paradigm and spatial- attention cueing processes are quantifiable by 10 months with the Delayed Response paradigm. Performance improved from 6-12 months and longer delays impaired performance. Study 2 examined whether fragile VSTM abilities were responsible for infants’ A-Not-B error, a phenomenon often observed when searching for an object hidden at one of two locations (A and B). Six to 12-month-olds were assessed on a looking A-Not-B task as well as on Delayed Response and Change Detection to assess links between performance. Individual differences in VSTM performance were not predictive of A-Not-B error performance, providing evidence that VSTM accounts may not solely provide explanation of A-Not-B error. Study 3 assessed whether individual differences in 8-month-olds’ neural band power was predictive of their VSTM performance. Infants’ continuous EEG was recording during Change Detection as well as during a baseline resting-state. Results suggest the early alpha band modulates VSTM performance, with decreases in alpha band power shown for higher performers and increases in alpha band power shown for lower performers, relative to baseline. Theta band power was not found to be related to VSTM performance. These outcomes help inform the understanding of infant VSTM and its emergence throughout early development.

This work aimed to understand the limits and capabilities of implicit sequence learning, or internalizing statistically-defined regularities in a stream of stimuli without awareness or intention to learn. Both spatial and nonspatial informational components were manipulated in presented streams of stimuli, and undergraduates learned regularities in both categories of information and applied this knowledge to test trials. Evidence for a unique contribution of a spatial component to visual implicit sequence learning was presented, and changes in performance across the quarter were examined. This work supported a model of implicit learning as a general principle of neural processing (Reber, 2013) and a model of unidimensional and multidimensional systems involved in implicit sequence learning (Keele et al., 2003).

Autism spectrum disorder (ASD) is a highly prevalent, lifelong condition characterized by impairments in social communication and the presence of restrictive, repetitive behaviors. Identifying the earliest signs of ASD is a critical factor in promoting optimal long-term outcomes for those affected. The developmental origins of ASD, including symptom onset and progression, remain poorly understood. Current known markers of ASD are centered on deviations in social and communicative skills that typically emerge around the first birthday; however, the presence of overt impairments reflects the consequence of an altered trajectory of social development, rather than the causes and underlying mechanisms from which these impairments arose. This has motivated the search for early risk markers more proximal to the source of deficits, including aberrations in early emerging neural systems that scaffold social development.

Prior behavioral research has primarily focused the search within a single developmental domain, but this approach has fallen short of identifying reliable markers of ASD risk within the first 12 months. Instead, infants who develop ASD may exhibit impairments across several developmental domains, including diminished social attention in both visual and auditory domains as well as atypical brain organization in early infancy. This dissertation builds upon these bodies of research to provide a comprehensive profile of ASD risk in early infancy. The studies take a multimodal approach and employ eye-tracking, task-based and resting-state functional neuroimaging, and behavioral measures to investigate developmental antecedents of the social deficits and other core behavioral symptoms associated with ASD across early emerging domains critical for social development.

Study 1 used eye-tracking methods to examine visual social attention to faces from 3- to 12-months of age in infants at high- and low-risk for ASD, as well as factors that may moderate developmental trajectories. Greater parental affectedness of ASD-related behaviors predicted slower developmental increases in attention to faces, indicating that parents’ social communicative skills influence their infant’s social development. Moreover, developmental trajectories in face-looking in high-risk infants predicted social communicative functioning. Altogether the findings suggest that parent-mediated interventions targeting parent-child interactions may have positive effects on social communicative development in infants with familial risk for ASD.

Study 2 used a passive listening stimulus-evoked functional magnetic resonance imaging (fMRI) paradigm to evaluate native language processing (i.e., auditory social attention) in 1.5 and 9-month-old infants at familial risk for ASD. At 1.5 months, high-risk infants already showed evidence for suboptimal language processing. At 9-months, high-risk infants exhibited attenuated neural responses to language relative to their low-risk peers, and this effect was particularly pronounced in high-risk infants who later displayed delayed language development. Severity of social impairments was higher for high-risk infants with delayed language than those without. Deviations in language processing may constitute an early marker of social communicative difficulties associated with ASD risk.

Study 3 combined eye-tracking and resting-state fMRI methods to evaluate Salience Network connectivity at 6 weeks and its association with subsequent social communicative skills and sensory processing abilities. Six-week-old high-risk infants demonstrated hyperconnectivity with sensorimotor regions, whereas low-risk demonstrated hyperconnectivity with prefrontal regions involved in social attention. Infants with higher connectivity with sensorimotor regions had lower connectivity with prefrontal regions, suggesting a direct attentional tradeoff for sensory versus socially-relevant information. Alterations in network connectivity at six weeks predicted 12-month ASD symptomatology, providing the earliest mechanistic account for the unfolding of atypical trajectories associated with ASD risk. Initial disruptions in brain systems involved in sensory/attentional processes are a critical antecedent to the later-emerging social symptoms of ASD. Taken together, the findings from these studies indicate that a multimodal approach that includes early brain-based measures has the incredible potential to improve the early detection of ASD risk as well as uncover mechanisms associated with the emergence of ASD symptomatology within the first few weeks of postnatal life.

What are the developmental implications and underlying mechanisms of atypical responsiveness to joint attention (RJA) in autism? A longitudinal investigation of relations between individual differences in early childhood RJA and adult outcomes revealed associations between early joint attention and adult adaptive skills, symptoms and social functioning. Many of these associations were attributable to relations between RJA and subsequent changes in cognitive and linguistic skills which in turn predicted adult skills and symptoms. A second longitudinal study assessed relations between an eye-tracking measure of social responsiveness and gaze following administered in infancy and subsequent symptoms and diagnoses of autism. Social responsiveness, specifically interest in dyadic cues, but not gaze following was associated with subsequent autism diagnoses. A third study used eye-tracking and in-person assessments to examine three potential mechanisms underlying atypical gaze following in autism: impaired reflexive gaze cueing, difficulty integrating gaze and affect or reduced recognition of the referential significance of gaze. Reduced low- and high-level gaze following were associated with autism while difficulties with reference were related to developmental level rather than autism. No evidence of gaze and emotion integration was observed regardless of diagnosis. Thus, reduced RJA in autism may arise from low-level atypicalities in gaze following while impaired integration of gaze and affect and reduced understanding of reference may emerge with development. Together these studies imply that individual differences in dyadic and triadic aspects of social attention probably arise from low level mechanisms and have long-term implications for individuals with or at-risk for autism.

Beginning early in life, infants become familiar with specific kinds of voices and faces through undergoing countless repeated experiences with them. Consequently, infants quickly develop heightened sensitivity for these familiar audiovisual stimuli over the unfamiliar counterparts. In particular, infants are very familiar with happiness as it is ubiquitously present in their social environment. The present study has a two-fold objective. In a series of four studies, it aims to investigate how infants' respond to happiness across modalities and how the perception of happiness influences the way infants perceive familiar and unfamiliar faces, by measuring their eye movements on various types of faces. The first study examines the development of infants' perception of facial, vocal, and intermodal expressions of happiness and sadness in 5- and 8-month-olds. The second study examines 3- and 5-month-olds' differential response to infant-directed (ID) and adult-directed (AD) faces and how speech influences their looking behavior to faces. The third study further examines how much of infants' preferential response to ID faces can be explained by their overall preference for happy faces. Finally, the fourth study examines if infants' heightened sensitivity to happiness would affect the way they process own- and other-race faces by examining the other-race effect (ORE) in 9-month-old Caucasian infants. Overall, the present series of studies provide comprehensive body of evidence for infants' familiarity with and preference for happiness across different stages of their development within the first year of life. Furthermore, it demonstrated that the use of happiness in faces facilitated infants' discriminatory ability in both own- and other-race faces.