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Predicting Positive Affect in Infancy

Tobias Grossmann1, Halle Miller1, Olivia Allison1

  • 1Department of Psychology, University of Virginia, Charlottesville, USA.

Developmental Science
|April 25, 2026
PubMed

Insights

Infant biology and social engagement at 5 months predict positive affect (PA) at 7 months. These infant-specific factors, including CD38 genotype and cortisol, explain 27% of PA variance, highlighting early developmental foundations.

Area of Science:

  • Developmental Psychology
  • Behavioral Genetics
  • Neuroendocrinology

Background:

  • Positive affect (PA) is crucial for health and development.
  • Early origins of PA are not well understood.
  • Investigating infant-specific predictors of early PA is essential.

Purpose of the Study:

  • To examine infant-specific biological and social-behavioral factors predicting PA.
  • To determine if maternal factors also predict infant PA.
  • To understand the early foundations of positive emotional development.

Main Methods:

  • Assessed infant CD38 genotype, salivary cortisol, and social engagement at 5 months.
  • Measured infant PA using the Positive Emotionality/Surgency (PEm) factor at 7 months.
  • Utilized a pre-registered, longitudinal cohort study with 78 infants and mothers.

Main Results:

  • Infant CD38 genotype (AA/AC) predicted higher PA.
  • Lower infant cortisol levels were associated with higher PA.
  • Higher infant social engagement predicted higher PA.
  • Infant-specific factors explained 27% of the variance in infant PA.
  • Maternal measures did not predict infant PA.

Conclusions:

  • Early positive affect is influenced by infant-specific biological and behavioral factors.
  • CD38 genotype, cortisol, and social engagement are key early predictors of PA.
  • Findings support an infant-centric model of early affective development.

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