Fathers' Infant-Directed Speech in a Small-Scale Society.

When speaking to infants, mothers often alter their speech compared to how they speak to adults, but findings for fathers are mixed. This study examined interactions (N = 30) between fathers and infants (Mage  ± SD = 7.8 ± 4.3 months) in a small-scale society in Vanuatu and two urban societies in North America. Fundamental frequency (F0 ) and speech rate were measured in infant-directed and adult-directed speech. When speaking to infants, fathers in both groups increased their F0 range, yet only Vanuatu fathers increased their average F0 . Conversely, North American fathers slowed down their speech rate to infants, whereas Vanuatu fathers did not. Behavioral traits can vary across distant cultures while still potentially solving similar communicative problems.