Informed consent was obtained from a parent prior to data collection, which occurred in the Physical Therapy Movement Laboratory at the University of Scranton. Each infant in the full-term group was scheduled for data collection within 7 days after birth, at 6 weeks, and at 12 weeks. Each infant in the pre-term group was scheduled for data collection within 7 days of term age, at 6 weeks adjusted age, and at 12 weeks adjusted age. Families were offered a ride with a professional driving service to and from the laboratory for all 3 visits.