“We were quite surprised that the timbre shift we found for English mothers exhibited such a consistent pattern across so many diverse languages,” lead study researcher Elise Piazza, a neuroscientist at Princeton University, told Newsweek in an email. “These mothers were native speakers of one of these nine languages, and we asked them to speak only in that non-English language during all recordings.”

The team still isn’t quite sure why we change our timbre when speaking to children. They hypothesize that it may be a way for mothers to shift their children’s attention to them from the time they are born, but this remains to be confirmed.