There's a new wrinkle in the debate over pacifier use—and it has nothing to do with future dental bills or interventions by the Binkie Fairy. According to a new study from the University of Wisconsin-Madison, pacifiers may stunt the emotional development of baby boys because—much like face-freezing effects of Botox—pacifiers hinder babies' ability to mimic the facial expressions of those around them, a practice that is considered essential to healthy emotional development.
In three separate experiments conducted by UW-Madison psychologists, researchers found that among a group of 6- and 7-year-old boys, those whose parents reported frequent pacifier use during infancy were the least likely to mimic the emotional expressions of faces seen in a video. In another group, college-aged men who reported (by their own recollections or their parents') more pacifier use as kids scored lower than their peers on emotional aptitude tests.
Psychologists say the effect is similar to that seen in studies of patients receiving injections of Botox to paralyze facial muscles and reduce wrinkles. Botox users experience a narrower range of emotions and often have trouble identifying the emotions behind expressions on other faces.
"That work [on Botox] got us thinking about critical periods of emotional development, like infancy," says Dr. Paula Niedenthal, UW–Madison psychology professor and lead author of the study (via a university press release). By reflecting what another person is doing, you create some part of the feeling yourself, Niedenthal explains. So what happens, she pointedly asks, when "you always had something in your mouth that prevented you from mimicking and resonating with the facial expression of [your parents and care givers]?"
And what about girls? In this current batch of studies, pacifier use had little to no impact on girls' emotional development. This could be because girls develop earlier (and differently) in some key areas, says Niedenthal, making it possible that they make sufficient progress in emotional development before or despite pacifier use. "It may be that boys are simply more vulnerable than girls, and disrupting their use of facial mimicry is just more detrimental for them," she notes.
Still, it's not necessarily time to trash every binky in the house. "Not all pacifier use is bad at all times..." admits Niedenthal, adding, "We already know from this work that nighttime pacifier use doesn't make a difference, presumably because that isn't a time when babies are observing and mimicking our facial expressions anyway. It's not learning time."