Mothers tend to address their babies in a particular way. Their tone of voice softens and their words are clearly articulated. But why do they naturally adapt their speech? Do they do it systematically? In a study published in the Journal of Child Language, a team of researchers from Virginia Tech, École normale supérieure-PSL and Pacific Lutheran University recorded and analysed the speech of ten mothers to their six-month-old child, to puppies and to adults. They found that the mothers' speech to their babies and puppies was particularly clear and articulate. This clarity seems to be linked to a positive emotional state aroused by the babies and puppies.
Mothers speak more clearly when talking to infants and parrots, compared to when they talk to adults or their own cats and dogs. What do parrots and infants have in common?
Some researchers thought that mothers spoke more clearly because they were trying to teach language: after all, both babies and parrots are learning to talk. But in other studies, natural recordings of mothers’ speech to infants showed they speak more and less clearly! So what else is going on? A study led by Robin Panneton (Virginia Tech) has gone deeper into this issue by recording mothers talking to babies, puppies, and adults.
"We wanted to better understand why some mothers seem to hyperarticulate more than others, across both circumstances and cultures", said Dr. Robin Panneton when asked about the reason for doing this research.
Robin Panneton (Virginia Tech), Alejandrina Cristia (ENS-PSL), Caroline Taylor (Virginia Tech) and Christine Moon (Pacific Lutheran University) initially thought that mothers spoke more clearly when they were teaching babies to speak.
At first, the team anticipated that if mothers speak more clearly to teach language, then they'd speak more clearly when talking to babies, but not to puppies, as compared to when they talked to adults. However, perhaps mothers speak more clearly when they are feeling more positive emotions. That is, perhaps the parrots used in previous studies seemed cuter than the dogs, and elicited more positive vocal valence. So if the latter idea was right, and the puppies in this study elicited as much positive emotion as babies did, then mothers would speak more clearly when talking to babies and puppies than to adults.
To test these competing explanations (teaching versus positive emotion), the team performed a study which analysed the speech of ten American mothers of six-month-old infants. Mothers were taken into a room and digitally recorded, while speaking about three different objects to an infant, a puppy, and an undergraduate assistant. Mothers described each object, talked about its characteristics, and sometimes its function. Then, the recordings were analysed for positive valence and vowel analysis.
Surprisingly, the team found that mothers expressed more positive emotion to both infants and puppies than to other adults. And they hyperarticulated their speech when speaking to babies and puppies compared to when speaking to adults. Therefore, when speaking to an infant or a puppy, mother’s display an array of positive emotions that changes their vocalisations.
This finding has implications for looking at maternal speech from a multi-faceted perspective that includes, but is not limited to, her emotional state. This means that speaking more clearly and less clearly is typical across mothers, but for a variety of reasons.
In sum, when a mother expresses a positive emotional state, her voice becomes hyperarticulated which leads to a clearer pronunciation of the words, making language processing easier. So it's not about either teaching or having fun - it's both!
Robin Panneton, Alejandrina Cristia, Caroline Taylor and Christine Moon (2023). Positive Valence Contributes to Hyperarticulation in Maternal Speech to Infants and Puppies. Journal of Child Language, 1-11. doi:10.1017/S0305000923000296
Alejandrina Cristia, directrice de recherche CNRS
Laboratoire de Sciences Cognitives et Psycholinguistique (EHESS, ENS-PSL, CNRS)