Neurohormones and temperament interact during infant development.

The infant's psycho-physiological regulatory system begins to develop prenatally and continues to mature during the postnatal period. Temperament is a construct comprising tonic individual differences in dispositional physiological and behavioural reactions as well as an evolving ability to regulate to environmental conditions. Theoretical models and research have shown that neurohormonal and -physiological factors contribute to individual development and impact infant behaviours as well as the developing regulatory system. Moreover, prenatal maternal risks such as stress and depression are thought to programme fetal regulatory tendencies and that influences neural and behavioural functioning in infancy. The purpose of this review is to examine the theories and research that link infant temperament to neurohormonal and -physiological development in typically developing infants and in those exposed to environmental risk. Research has demonstrated associations between individual variation in physiological stress responses and regulation (measured with cortisol). Moreover, studies have noted an association with physiological regulation and socio-emotional interaction (as measured by the touch-oxytocin link) that may buffer emotional dysregulation. The interaction between individual differences in temperamental tendencies, neurohormonal and -physiological patterns will be discussed by presenting data from studies that have shown that infant neurohormonal and -physiological functioning sets an important trajectory for the development of the individual.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.