Language has long been identified as a powerful communicative tool among humans. Yet, pre-linguistic communication, which is common in many species, is also used by human infants prior to the acquisition of language. The potential communicational value of prelinguistic vocal interactions between human infants and mothers has been studied in the past decades. With 120 dyads (mothers and 3 or 6-month-old infants), we used the classical Still-Face Paradigm (SFP) in which mothers interact freely with...