The Costs and Benefits of Development: The Transition From Crawling to Walking.

The transition from crawling to walking requires infants to relinquish their status as experienced, highly skilled crawlers in favor of being inexperienced, lowskilled walkers. Yet infants willingly undergo this developmental transition, despite incurring costs of shaky steps, frequent falls, and inability to gauge affordances for action in their new upright posture. Why do infants persist with walking when crawling serves the purpose of independent mobility? In this article, we present an integrative analysis of the costs and benefits associated with crawling and walking that challenges prior assumptions, and reveals deficits of crawling and benefits of upright locomotion that were previously overlooked. Inquiry into multiple domains of development reveals that the benefits of persisting with walking outweigh the costs: Compared to crawlers, walking infants cover more space more quickly, experience richer visual input, access and play more with distant objects, and interact in qualitatively new ways with caregivers.