Sequential analyses of postural reactions in nonhandicapped infants.

The purpose of this study was to identify an empirically validated sequence of automatic postural reactions in a sample of 40 nonhandicapped infants. Using a cross-sectional design, we tested infants between the ages of 2 and 10 months for the presence of full and partial righting, equilibrium, and protective reactions. Two types of sequential analyses were performed. The Thurstone absolute scaling technique identified an age-related sequence, and the scalogram technique yielded a measure of the variability of the sequence. The sequence of postural reactions defined in this study is in general agreement with the sequence reported in previous clinical reports, although some differences in ordering are noted. A consistency index of .727 indicated that the sequence of postural reactions had fairly good predictive ability. This study contributes a data-based sequential model of postural reactions and an indication of the degree of sequential variability in the order of emergence of postural reactions in nonhandicapped infants. Definition of the sequence and the observed variability in nonhandicapped infants is an initial step in the understanding of the processes underlying the development of postural reactions.