The sleep patterns of 41 full-term newborn infants were recorded continuous
ly during the first 2 postnatal days. The recordings were made nonintrusive
ly using the Motility Monitoring System while the infants were in the hospi
tal. When the subjects were 8 months old, their mothers filled out the Infa
nt Temperament Questionnaire, which yields scores on nine dimensions of tem
perament. There were four significant correlations between Day 1 sleep meas
ures and later temperament dimensions; there were eight correlations on Day
2, hardly more than a chance number. The temperament scores were used to c
lassify infants as having Easy, Intermediate, Difficult, or Most Difficult
temperament. Profiles of sleep measures for the infants in the four groups
differed significantly on Day 1, and the Most Difficult infants showed the
most extreme values on all measures. Differences in the predictive findings
from Day 1 and Day 2 were attributed to the greater influence of the stres
s of labor and delivery on the first postnatal day.