Parents who don't want their baby boys to grow up emotionally stunted may want to pocket their pacifiers during the daytime.
A new study from the University of WisconsinMadison suggests frequent pacifier use during the day may disrupt the emotional development of baby boys because it limits their opportunity to mimic the facial expressions of others - a tool that may help them better understand emotions and learn empathy.
Girls appear to make sufficient progress emotionally, despite pacifier use, suggests the research published in a recent issue of the journal Basic and Applied Social Psychology.
Humans of all ages read each other's emotions partly by mimicking their facial expressions, which helps them process what the person is thinking and feeling by creating some part of the feeling for themselves, says the study's lead author, Paula Niedenthal, a University of Wisconsin psychology professor.
A baby with a pacifier in his mouth is less able to mirror expressions and the emotions they represent, she said.
Niedenthal and her team of researchers conducted three studies to test the relationship between pacifier use and emotional information processing, both in the United States and in France.
In the first study, researchers found six-and seven-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, collegeaged 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."
The study's results are suggestive, and should be taken seriously, Niedenthal said.
But she acknowledged further research is needed.
Figuring out why girls seem to be immune - or how they compensate - is an important next step, Niedenthal said.
Ruby Natale, assistant professor of clinical pediatrics at the University of Miami School of Medicine, co-wrote the book Pacifiers Anonymous: How to Kick the Pacifier or Thumb Sucking Habit.
The book notes that roughly 75 per cent to 90 per cent of all infants suck a pacifier or thumb. In the past, thumb-sucking was the No. 1 choice.
But the latest estimates of pacifier use in the U.S. puts it at about 74 per cent. One study found 20 per cent of children sucked pacifiers beyond age three.
