Sticky mittens, prickly Velcro, and infants' transition into independent reaching: Response to Williams, Corbetta,...

Williams, Corbetta, and Guan (2015) report findings on the effects of active and passive motor training in three-month-old infants and argue that passive task exposure is sufficient to encourage future reaching behaviors. In this commentary, we relate these new findings to our body of published work using sticky mittens and describe important differences in the materials and procedures used. In particular, Williams et al. (2015) used modified sticky mittens that allowed infants' fingers to make direct contact with prickly Velcro on the toys, and they used a different training procedure that required infants to discover the hidden functionality of the sticky mittens by themselves. We argue that these differences explain the apparent conflicts between our prior work and the results reported by Williams et al. (2015). The Williams study presented infants with a learning context that was quite different from the one infants encountered in our research, and so it is not surprising that infants in their study showed such different patterns of behavior.