Infants--Development

Infants have an innate desire to form social bonds and jealousy protests are an attempt to regain exclusive maternal attention from a social usurper. The current study examined neurophysiological and bio-hormonal processes related to jealousy responses during the first year and a half of life. Prior to and after the first year of life, infants express jealousy protest behavior when faced with a social threat. Resting-state frontal EEG coherence indicated a developmental shift from bilateral connectivity in younger infants to increased frontal specialization in older infants in relation to jealousy responses. Furthermore, 6- to 9-month-old infants exhibited more frontal neuroconnectivity in the right hemisphere (i.e., an area related to negative emotions) of the brain compared to left when faced with social threat. Lastly, social threat activated HPA reactivity in infants higher in temperamental distress. This study provides further evidence for the emerging links between physiological and socioemotional responses in infancy due to loss of exclusive maternal attention.

Temperament and its development have been associated with the alpha band of EEG coherence in previous research that focused on adolescent and adult populations, results suggest that this measure stands as a reliable indicator of emotional states. In the current study, five data sets from previously conducted studies were analyzed to determine if resting state alpha coherence measures differ in various brain regions and are associated with variation in levels of temperament. Additionally, we aimed to determine if, as age increases, a synchronous result in coherence may be seen (specifically, from posterior to anterior), in accordance with neurophysiological development. Regression analyses suggested that the negative affectivity temperamental qualities did not significantly associate with coherence. Repeated-measures analyses yielded significant results in favor of the electrocortical development hypothesis and, through exploratory analysis, more reactive temperament scores depicting positive affectivity, emotional/self-regulation, and activity level displayed in infants who had higher coherence in posterior regions. The study was suggestive of high coherence values associating with highly reactive temperamental attributes in posterior regions in the 3- to 12-month-old participants and higher coherence values displaying in posterior regions compared to anterior regions consistently across age groups.

The mobile conjugate reinforcement (MCR) paradigm, made famous by Carolyn Rovee-Collier and her colleagues (Rovee & Rovee, 1969), has long been used to study infant learning and memory. In MCR studies, the infant's foot is tethered to a mobile hanging overhead, and the mobile responds directly to the infant's kicking. Infant kicking rate triples within a few minutes of interacting with the mobile. This result was classically interpreted as evidence of reinforcement learning. Kelso and Fuchs (2016) reinterpreted it as evidence that a coordinative structure, or functional synergy, forms between infant and mobile, triggering a positive feedback loop between the two. Positive feedback is proposed to give rise to an `Aha!' moment as the (prelinguistic) infant suddenly realizes it is an agent in control of the mobile's motion. While some have theorized the realization of self as causal agent emerges from organism-environment interactions, Kelso and Fuchs (2016) developed a mathematical model of the coordination dynamics between the infant and mobile, providing mechanistic explanations for the formation of agency. The current study was the first to measure movement of the mobile and analyze how dynamics of coordination between infant and mobile relate to possible transitions from spontaneous to intentional action. Novel measures of infant and mobile dynamics were used to test model predictions. Infant activity dropped drastically in response to non-contingent mobile movement and remained suppressed at the start of infant~mobile contingency, suggesting that mobile movement triggers a qualitatively different context for infants. This finding challenges the widely held assumption that mobile movement rewards and stimulates infant movement and calls into question the sufficiency of standard contingency detection cut-offs and explanations of conjugate reinforcement learning. Assessing coordination dynamics on a fine time scale using new analytical techniques made it possible to identify moments of agentive realization. Approaching agency as a relational phenomenon allowed for detailed characterization of the infant~mobile relationship and its role in the emergence of causal agency. In addition, the results revealed a number of surprising insights into agency formation such as the critical role of inactivity for agentive discovery and the possibility of intermediary stages or quasi-agentive states.