Acoustic properties of the cries of 14 infants were evaluated at both 2 and 4 weeks of age when the infants were lying in a supine position and when they were sitting upright in a car seat. In the upright position, infants' breathing was more rapid and showed less individual variability. The fundamental frequency of their cries increased in the…

Used multilevel analyses to examined the amounts of time infants spent asleep, awake, content, feeding, fussing, and crying at 2, 6, 12, and 40 weeks of age. Found that day-to-day fluctuations accounted for between 44 and 53% of the variance in amounts of time sleeping, fussing, and crying. (MDM)