This dissertation explores in a series of four studies using a developmental perspective the nature of infant sleep and its relation to waking experiences. The first two studies suggest that the sleep disturbance, which is usually observed in the second half of the first year of life, is related to a major transition of the infants becoming effectively mobile through learning to crawl on hands and knees. The sleep disruptions are mainly explained by infants<&lsquo> heightened sensitivity to proximity of a caregiver as a result of the developmental shift initiated by the onset of crawling. Thus, the findings call for consideration of the <&ldquo>sleep disturbance<&rdquo> as a normal developmental phenomenon that should not be treated as a clinical problem but rather accepted with sensitivity from the parents. Based on the third study of the dissertation, however, parents often apply sleep-training techniques involving prolonged periods of infant crying during the same age period and sometimes as a reaction to the <&ldquo>sleep disturbance<&rdquo>. The sleep training is widely recommended together with solitary sleeping arrangement and the study findings demonstrate that the recommendations have a profound effect on parental decisions. However, the fourth study does not support the benefits of the recommendations. Based on the findings, sleep training is not associated with a better sleep. Instead, sleep-trained infants cry more at night and also have a worse mood in the morning. Night feeding, on the other hand, is associated with less crying both at night and during the day. Even though it is also associated with more time awake at night and less self<&ndash>soothing, it does not seem to affect the overall amount of sleep. In addition, the nature of <&ldquo>self<&ndash>soothing<&rdquo> as a self<&ndash>regulatory ability is questioned by the findings reported in the fourth chapter, since it does not appear to be related to the infant's daytime self-regulatory abilities. Though closer sleeping location and higher parental involvement at night are associated with more interrupted sleep, it is also related to better daytime behavioral outcomes in the infants. Together the findings of this dissertation suggest that the <&ldquo>sleep disturbance<&rdquo> in infancy might be normal for this phase of development, and recommendations given to parents should be carefully examined since those are affecting both infant and parents as one.

Whether motoric activities hold psychological effect has been a controversial. Recently, Campos and his colleagues (Campos et al, 2000) have shown the acquisition of prone locomotion not only precedes but also causes various changes in psychological abilities, including perception, cognition, and socio-emotional development. This dissertation work deals with another major motoric achievement during infancy, upright locomotion, and whether it brings about psychological changes. It focuses on an original phenomenon that walking brings about increased receptive and productive vocabularies (Walle & Campos, 2014). If this relation reflects the consequence of an epigenetic event, then it should be present regardless of when the infant typically begins to walk, the infant’s culture, and the infant’s native language. This study sought to replicate the previously reported link between walking and language development in American infants and investigate whether this relation exists cross-nationally in typically developing Chinese infants exposed to Mandarin. Urban Chinese infants not only provide a distinct linguistic and cultural population in which to study this relation but also typically begin walking approximately 6 weeks later than American infants. Our results demonstrated that (1) walking infants in both the American and Chinese samples had greater receptive and productive vocabularies than same-aged crawling infants, (2) differences between crawling and walking infants were proportionally similar in each sample, and (3) the walking-language relation was present for both noun and non-noun vocabularies. These findings provide further support of a relation between infant walking onset and language development, independent of age. Avenues for future research of the processes involved in this relation, as well as additional populations of interest to investigate, are discussed.

Appreciating authentic and inauthentic emotional communication is central to the formation of trusting and intimate interpersonal relationships. However, when infants are able to discriminate and respond to inauthentic emotion has not been investigated. The present set of studies was designed to investigate infant sensitivity to three specific cues of inauthenticity: the contextual congruency of the emotion, the degree of exaggeration of the emotion, and the clarity with which the emotion is communicated. In each experiment, 16- and 19-month-old infants were presented with an emotional communication in which an inauthentic cue was present or absent. Infant behavioral responding to the emotional context was observed and coded. In all three experiments, 19-month-old infants, but not 16-month-old infants, detected inauthentic emotional communication and differentially responded to the environment accordingly. These findings demonstrate that infants do not simply take all emotional communication at face value and are sensitive to features of emotional contexts beyond what is expressively communicated by the adult. Possible developmental mechanisms that may account for the observed developmental shift in infant emotional development are proposed, and implications for the present findings on future research in emotion and emotional development are highlighted.

Interpersonal conflict management is a context in which empathy and emotion regulation can be both challenging and of vital necessity. The present study examined the effects of empathic communication on conflict management between mother-adolescent dyads (N = 50). Mother-adolescent dyads engaged in a 10-minute discussion of a topic of frequent conflict in their relationship. Following the discussion, mothers and adolescents independently completed a post-conflict discussion questionnaire to assess their satisfaction with the discussion. Emotional behaviors during the discussion were coded using the Specific Affect Coding System (SPAFF). Empathic communication was coded as (1) validation and (2) interest in the other's perspective and feelings. The present study explored several questions related to (1) adolescent age differences in mother and adolescent empathic communication and conflict management, and (2) relations between empathic communication and conflict management. Notably, older adolescents and their mothers displayed more validation than younger adolescents and their mothers. Furthermore, mother's validation was marginally positively correlated with adolescents' satisfaction with the discussion, and this relation was mediated by the degree to which adolescents perceived that their mother understood their point of view and feelings during the discussion. Findings indicate that empathic communication in response to adolescent negative emotion plays a unique role in effective conflict management between mothers and adolescents. Implications for research on empathy and interventions targeted at facilitating effective conflict management between parents and adolescents are discussed.

The moral prohibition against harming others is fundamental to any social unit, including families with young children. Yet, infants appear less averse to harming others than do older children and adults. Infants' harmful actions may in turn elicit strong reactions from others that could contribute to the acquisition of morality.

The present study investigated two main propositions: 1) mothers respond differently to infants' harmful acts against others (moral transgressions) than when intervening on transgressions related to infants' own well-being (prudential transgressions) or the creation of inconvenience, such as spilling (pragmatic transgressions). 2) Most infants harm others even without provocation. Twenty-six infants and their families participated in a 2.5-hour naturalistic home observation when the infant was 14 months old. Most of the families participated in additional visits when the infant was 19 (N = 24) and 24 (N = 22) months of age.

All infants who participated in three visits had at least one instance of purposefully harming others and 82 percent did so without any provocation or sign of distress. The hourly frequency of unprovoked purposeful harm showed a curvilinear relation to age (Visit 1: 0.85, Visit 2: 1.42, Visit 3: 1.27). Compared to their interventions on prudential and pragmatic transgressions, mothers' interventions on moral transgressions involved increased use of physical interventions and direct commands, decreased use of softening interventions or distractions, and decreased relenting or compromising. Mothers also rated it as more important to discourage their children from moral transgressions than to discourage their children from prudential transgressions. These findings suggest that caregiver responses to transgressions provide unique opportunities for the early acquisition of the moral prohibition against harming others.