Individual Differences in Physiology, Behavior, and Temperament Over the First 15 Months of Life

121 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.The relationship between individual differences in newborn physiology and behavior and 15-month developmental outcome was investigated. Forty-four healthy infants who had participated in a newborn study of physiological correlates of behavior were again tested at 15 months. During the newborn assessment, ten minutes of heart rate pattern and respiration data were collected and the Neonatal Behavioral Assessment Scale (NBAS) was administered. The 15-month assessment consisted of another ten minute recording of cardiorespiratory data and administration of the Bayley Scales of Infant Development, the Bates Infant Characteristics Questionnaire (ICQ), and a questionnaire of developmental milestones. Heart period, heart period variability, and an index of neural control of the heart by the vagus (i.e., vagal tone, V,) were analyzed from the cardiorespiratory data.Neonatal vagal tone was found to predict later cognitive and motor development. Infants with higher levels of newborn vagal tone scored higher on the Bayley Scales of Mental and Motor Development at 15 months, sat-up earlier, and stood-up earlier than infants with lower newborn vagal tone. Other cardiac measures were not as sensitive to developmental outcome as V. Measures of neonatal heart rate pattern were also related to temperament characteristics at 15 months, indicating a relationship between physiology and behavioral style. The NBAS was not predictive of later cognitive development, but was significantly related to later temperament dimensions. Comparison of ratings on the NBAS, the ICQ, and the Bayley Infant Behavior Record indicated stability in "easiness-difficultness" over the first 15 months of life, and consistency in parental and experimenter ratings of temperament at 15 months.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD