Equifinality in infancy: The many paths to walking.

Many different pathways can lead to the same result or developmental outcome. What are the developmental routes that result in the onset of walking? In this longitudinal study, we documented patterns of infant locomotion during everyday activities at home for 30 prewalking infants. Using a milestone-based design, we focused on observations spanning the two months before the onset of walking (M age at walk onset = 11.98 months, SD = 1.27). We examined how much time infants spent in motion and when they moved, whether they were more likely to do so while prone (crawling) or upright with support (cruising or supported walking). Results showed immense variability in infants' practice regimes en route to walking-some infants spent relatively similar amounts of time crawling, cruising, and supported walking at each session, others preferred one method of travel over the alternatives, and some switched between different types of locomotion from session to session. In general, however, infants spent a larger share of their movement time in upright positions compared to prone. Finally, our densely sampled dataset revealed a clear feature of locomotor development: infants follow many distinct and variable paths to walk onset, regardless of the age at which it is attained.