Temperament development in infancy: What we have learned about the origins of individual differences in the past 25 years.

The goal of this review article is to provide an overview of the last quarter century of infant temperament research. Beginning with a brief description of theoretical underpinnings, we focus on studies addressing early beginnings of reactivity and self-regulation. After the most widely accepted framework used to conceptualize temperament has been defined, the next section examines various methodologies for measuring temperament in the past 25 years. We then focus on work that aims to describe developmental changes and progression of temperament development. The following sections consider individual and contextual contributing factors, such as infant sex and cultural influences. Finally, we review infant temperament as a predictor of important child outcomes, focusing on behavior problems/symptoms. Overall, the past 25 years temperament research has increased our understanding of important developmental changes in different domains of reactivity and regulation, emphasizing biological underpinnings, such as underlying brain activity, as well as contributing factors (e.g., genetic/epigenetic contributions). The review ends with a discussion of remaining gaps in research and recommendations for future research, such as the need to harmonize datasets across laboratories to leverage latest quantitative methods resulting in reproducible science.