Intraindividual variability in infant behavior

Dev Psychol. 1999 Jul;35(4):1102-12. doi: 10.1037//0012-1649.35.4.1102.


Longitudinal observational data of infant crying, fretting/fussing, and smiling and the time spent in physical contact with the mother were used in a study on behavioral variability. The infants were followed weekly for a 15-month period. Evidence was found of an important intraindividual variability in the studied behaviors, specifically between the ages of 0 and 5 months, 5 and 10 months, but not between 10 and 15 months. Results are discussed and analyzed in the light of earlier literature. The possible functions and the factors underlying variability in development as well as its methodological implications are discussed.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Crying
  • Humans
  • Individuality*
  • Infant
  • Infant Behavior*
  • Longitudinal Studies
  • Mother-Child Relations
  • Personality Assessment
  • Smiling