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Longitudinal trajectories of infant posture. Each growth model displays developmental change in the proportion of intervals infants spent: (a) supine (lying on their backs); (b) supported sitting (with help from mothers, the Boppy pillow, or with their own hands); (c) independent sitting (with hands off the ground); or (d) transitioning between postures (e.g., from prone to sitting). Error bars show standard errors.
