Why the body comes first: effects of experimenter touch on infants' word finding.

The lexicon of 6-month-olds is comprised of names and body part words. Unlike names, body part words do not often occur in isolation in the input. This presents a puzzle: How have infants been able to pull out these words from the continuous stream of speech at such a young age? We hypothesize that caregivers' interactions directed at and on the infant's body may be at the root of their early acquisition of body part words. An artificial language segmentation study shows that experimenter-provided synchronous tactile cues help 4-month-olds to find words in continuous speech. A follow-up study suggests that this facilitation cannot be reduced to the highly social situation in which the directed interaction occurs. Taken together, these studies suggest that direct caregiver-infant interaction, exemplified in this study by touch cues, may play a key role in infants' ability to find word boundaries, and suggests that early vocabulary items may consist of words often linked with caregiver touches. A video abstract of this article can be viewed at http://youtu.be/NfCj5ipatyE.