There is ample empirical evidence for an asymmetry in the way that adults use positive versus negative information to make sense of their world; specifically, across an array of psychological situations and tasks, adults display a negativity bias, or the propensity to attend to, learn from, and use negative information far more than positive information. This bias is argued to serve critical evolutionarily adaptive functions, but its developmental presence and ontogenetic emergence have never seriously been considered. Here, we argue for the existence of the negativity bias in early development, evident especially in research on infant social referencing but also in other developmental domains. We discuss ontogenetic mechanisms underlying the emergence of this bias, and explore not only its evolutionary but also its developmental functions and consequences. Throughout, we suggest ways to further examine the negativity bias in infants and older children, and we make testable predictions that would help clarify the nature of the negativity bias during early development. KeywordsNegativity bias; Affective asymmetry; Social-cognitive development; Emotion; Social referencing Infants are exposed to a great deal of social information from birth, and their ability to use this information effectively is critical for development in many domains and for survival in general. This raises several important questions: do infants attend equally to all facets of this information, or do they attend to certain facets more than others? Do they, in addition, learn and remember particular kinds of information better than others? What evolutionary and developmental consequences do these ways of approaching the environment have? In this paper, we propose that infants display a negativity bias: that is, infants attend more to, are more influenced by, and use to a greater degree negative rather than positive facets of their environment. We propose possible ontogenetic pathways for the emergence of the negativity bias, and we argue that this bias serves important evolutionary and developmental functions.

SummaryIn human adults, voices are processed in specialized brain regions in superior temporal cortices. We examined the development of this cortical organization during infancy by using near-infrared spectroscopy. In experiment 1, 7-month-olds but not 4-month-olds showed increased responses in left and right superior temporal cortex to the human voice when compared to nonvocal sounds, suggesting that voice-sensitive brain systems emerge between 4 and 7 months of age. In experiment 2, 7-month-old infants listened to words spoken with neutral, happy, or angry prosody. Hearing emotional prosody resulted in increased responses in a voice-sensitive region in the right hemisphere. Moreover, a region in right inferior frontal cortex taken to serve evaluative functions in the adult brain showed particular sensitivity to happy prosody. The pattern of findings suggests that temporal regions specialize in processing voices very early in development and that, already in infancy, emotions differentially modulate voice processing in the right hemisphere.

While the nutritional and physical health benefits of breastfeeding are well established, accumulating research demonstrates the far-reaching psychological effects of breastfeeding on children and their mothers. Here, we provide a non-exhaustive review of the empirical evidence, showing that breastfeeding impacts children’s brain, cognitive, and socio-emotional development. In mothers, research is presented indicating that breastfeeding influences mood, affect, stress, and maternal care. The current review aims to provide a broad overview of existing findings on the psychological effects of breastfeeding, highlighting the important role that breastfeeding plays across several dimensions of psychological functioning. We also discuss the potential mechanisms that may underpin the observed effects, provide a constructive commentary on the limitations of the existing work, and put forth some considerations when evaluating this line of research.