Crawling and walking infants elicit different verbal responses from mothers.

We examined mothers' verbal responses to their crawling or walking infants' object sharing (i.e. bids). Fifty mothers and their 13-month-olds were observed for 1 hour at home. Infants bid from a stationary position or they bid after carrying the object to their mothers. Mothers responded with affirmations (e.g. 'thank you'), descriptions ('red box'), or action directives ('open it'). Infants' locomotor status and the form of their bids predicted how mothers responded. Mothers of walkers responded with action directives more often than mothers of crawlers. Notably, differences in the responses of mothers of walkers versus those of crawlers were explained by differences in bid form between the two groups of infants. Walkers were more likely to engage in moving bids than crawlers, who typically shared objects from stationary positions. When crawlers displayed moving bids, their mothers offered action directives just as often as did mothers of walkers. Findings illustrate developmental cascades, wherein Infants' locomotor status affects how infants share objects with mothers, which in turn shapes mothers' verbal responses.