'Baby talk' is an international language, according to a new study - and Kiwis are perhaps the biggest culprits.
When singing and speaking to young infants, people alter their voices in a way that is consistent across cultures, according to an international, peer-reviewed study published in Nature Human Behaviour this week.
'Baby talk' is a type of speech associated with an older person speaking to a child or infant, also referred to as caretaker speech, infant-directed speech, child-directed speech or child-directed language. As per a 2020 article for The Conversation, a good way to determine if you adopt an 'infant-directed' voice is by imagining a cute, cuddly six-month-old and telling them to 'look at the ball'. Alternatively, think about how you would say that same phrase to a co-worker or friend.
"The melody of your speech when you are talking to a baby is very different from when you talk to other adults - your pitch is higher, and it's also more animated, with lots of ups and downs," Associate Psychology Professor Melanie Soderstrom and Human Biology Professor Michael C. Frank wrote for The Conversation.
"The rhythm changes too - we speak in shorter bursts with longer pauses when talking with babies, and also exaggerate certain words, especially when naming things for them.
"People talking to babies also use simpler words, ask more questions, and even change the way sounds in some words are pronounced."
The findings suggest that the way in which humans speak and sing to infants - or baby talk - may have a common, evolved function.
To conduct the study, a team of researchers and international collaborators - including staff from the University of Auckland and Victoria University of Wellington - collected 1615 recordings of human speech and song from 21 cultures across six continents.
The authors then applied computational analyses to study the acoustic features that differentiate adult-directed and infant-directed vocalisations.
The computer analysis found that people adopt a higher voice when speaking to infants than they do when conversing with adults, but the pitch difference is larger in some societies than others.
However, some of the most substantial differences in pitch were found in recordings of New Zealand English, as gathered in windy Wellington. Comparatively, some societies speaking other languages didn't make as considerable of a leap in tone when speaking to children.
Evidence from many animal species indicates that vocalisations often have a clear function, such as alarm calls alerting others to nearby predators. Previous research in humans has shown that both lullabies and the way in which parents speak to children, or infant-directed speech, have a soothing effect on little ones. This suggests that these vocalisations may also have a common function, but cross-cultural evidence for this is limited.
The authors found that acoustic features consistently differed between infant-and adult-directed recordings. For example, infant-directed recordings had purer timbres, songs were more subdued, and speech had a higher pitch. They played the recordings to 51,065 people from 187 countries, who spoke a variety of languages, and found that listeners could guess when vocalisations were directed at infants more accurately than by chance.
The authors say the results add to our understanding of human speech and song, suggesting we alter our vocalisations towards infants in a way that is widely recognisable and consistent across cultures - and may serve a common function.
Despite 'baby talk' being widely recognised and used around the world, infant-directed speech has something of a bad reputation. According to The Conversation, parents of young infants often report being told not to 'baby talk' to their children by friends, family and even healthcare professionals.
However, a study of more than 2200 infants across 67 laboratories in 16 countries in 2020 found that babies around the world respond positively to baby talk. The research also indicated that because babies prefer to listen to infant-directed speech, baby talking is beneficial for their language development.
"How does all the baby talk benefit your baby? The most obvious way is simply by getting your baby's attention - all those melodic and rhythmic properties are great attention-getters for babies (and for adults too, for that matter, though they might give you a funny look). Getting a baby's attention is good," Profs Soderstrom and Frank wrote.
"The more language a child hears directed towards them, the more language they learn, and the faster they process the language they hear. Plus, infant-directed speech communicates emotions effectively and helps establish a bond between caregiver and infant."
So Wellingtonians, continue to coo to your heart's content - but perhaps keep the couples' 'baby talk' in the bedroom.