It is well documented that newborns and even fetuses know their own mother’s voice: non-nutritive sucking¹ and fetal heart rate increase² in response to the mother’s voice compared with the voice of a stranger. Even with this recognition by the infant, one observes that parents adjust their speech to their infants by exaggerating sounds and pitch as well as their facial expressions, opening their mouths wider and raising their eyebrows. This is called infant-directed speech in the article by Saito et al³ in this issue, formerly referred to as “motherese” or “parentese”. Although no one “teaches” parents to speak …