Three experiments by a team of researchers led by psychologists from the University of Wisconsin-Madison tie heavy pacifier use as a young child to poor results on various measures of emotional maturity.

The study, published September 18 by the journal Basic and Applied Social Psychology, is the first to associate pacifiers with psychological consequences. The World Health Organization and American Academy of Pediatrics already call for limiting pacifier use to promote breast-feeding and because of connections to ear infections or dental abnormalities.

Humans of all ages often mimic -- unwittingly or otherwise -- the expressions and body language of the people around them.