Have you ever heard new parents gushing over their smiling babies, only for someone to point out that babies don’t really smile?
That’s not quite true, according expert Dr. Emese Nagy, a psychology reader at the University of Dundee.
“There have long been signs that newborn smiles could signal positive emotions to some extent,” Nagy wrote for The Conversation. “Smiles have been noted in the first few days of life as a response to stroking of the cheek or the belly. Newborns also smile in response to sweet tastes and smells.”
Until the second half of the 20th century, scientists thought of babies as mainly “reflexive” beings, she explained. They believed babies didn’t feel or express emotions the same way they would as they aged, and that infants didn’t really have the social experience to interact with their parents or other adults.
Some doctors even thought babies didn’t feel or process pain the same way older humans did. Smiling babies were just responding to muscle twitches or a dirty diaper.
But data collected over the past couple of decades is showing how mistaken those beliefs were.
As early as 1872, Nagy said, Charles Darwin described his own children offering what seemed to be “real” smiles at only 45 days old.
“My own research has replicated these observations,” she said. “When we asked 957 parents to observe and record smiling in their children for a study, they reported the first ‘social smiles’ of their babies just after four weeks on average.”
How to tell socially smiling babies from those making random expressions? A social smile follows eye contact from the baby in question. A 1959 study Nagy cited found that few babies social smiled in the first two weeks.
“About 60 percent had socially smiled by three weeks, and almost all of them had socially smiled within the first month,” she said.
Part of the reason smiling babies were believed to simply be reacting rather and actually smiling is because it was difficult to observe cheek and eye movement when they grinned. “Real” smiles affect the eyes as well.
“However, when scientists micro-analysed facial movements, frame by frame, using a dedicated coding system, smiles from as early as one day of age were more often than not accompanied by cheek and eye movements,” Nagy said.