In the first study, researchers found 6- and 7-year-old boys who spent more time with pacifiers in their mouths as young children were less likely to mimic the emotional expressions of faces in a video they were shown. In the next study, college-aged men who reported (by their own recollections or their parents’) more pacifier use as kids scored lower than their peers on common tests of perspective-taking, one of many components of empathy.
The third study involved a group of college students who took a standard emotional intelligence test measuring the way they make decisions based on assessing the moods of other people. The men in the group who had heavier pacifier use as babies scored lower.
“What’s impressive about this is the incredible consistency across those three studies in the pattern of data,” Niedenthal said. “There’s no effect of pacifier use on these outcomes for girls, and there’s a detriment for boys with length of pacifier use even outside of any anxiety or attachment issues that may affect emotional development.”
Why the gender difference?
“It could be that parents are inadvertently compensating for girls using the pacifier because they want their girls to be emotionally sophisticated,” Niedenthal said. “That’s a girlie thing.”
Suggesting that a pacifier can have lifelong consequences is far from popular among parents, Niedenthal acknowledged.
“They take the results very personally,” she said.
The study’s results are suggestive, and should be taken seriously, Niedenthal said. But she acknowledged further research is needed.
“It’s fascinating and challenging to many assumptions made about emotional development,” said Joseph Campos, a professor of psychology at the University of California, Berkeley. “It makes students of emotional development take notice. But as professor, Niedenthal acknowledges, there is much more work to be done.”
Mothers report babies can show oral expressions of emotion, even with a pacifier in their mouth, Campos said. And there are other facial components of emotion, including eyebrows, cheeks and wrinkles around the eyes, not affected by a pacifier, he said.