Stability of serial assessments of motor and communication abilities in typically developing infants--implications for screening.
Neuromaturational theory and dynamic systems theory make different assumptions about the rate of development of motor and communication skills. The stability of fine motor, gross motor, and communication scores of infants was evaluated to test these assumptions. This longitudinal descriptive study evaluated infants in their homes at 9, 11, 13, 16, and 21 months of age. One hundred and two Canadian children of English-speaking parents classified as typically developing at 23 months of age using the Diagnostic Inventory for Screening Children Preschool Screen were included. The Peabody Developmental Motor Scales and the Communication Symbolic Behavior Scales-Developmental Profile were used to assess development at each time. Scores were stable if the 95% confidence intervals around the scores overlapped across all assessments. Correlations evaluated the relationship of scores in a domain over time (normative stability) as well as the relationship of scores between domains (ipsative stability). There was large variability in scores within an infant, among infants and across developmental domains. Typical development is nonlinear rather than occurring at a constant rate. Fine motor, gross motor, and communication skills appear to develop independently. These results have implications both for developmental screening policies and for early intervention programs. Screening should include multiple domains and multiple time points before referrals are made to early intervention programs.