The debate about pacifiers as useful aides to soothe crying infants versus developmentally stunting crutches has been with us for decades. This group of researchers from the University of Wisconsin and elsewhere set out to test the possibility that pacifier use was associated with a delay in emotional development. Their hypothesis was that increased pacifier use impeded emotional growth via decreased opportunities for facial mimicry which in other studies has been found to be related to understanding emotional states in others.
The article covered three different but related studies. The first study comprised 106 first and second graders from France. While some control of demographic variables was done, the authors did not control for early behavior. Pacifier use was assessed retrospectively and participants watched images of emotionally changing faces while their own expressions were recorded. A second study was conducted in college students who completed questionnaires regarding pacifier use (yes/no) and empathy, including the dimension of perspective taking. A third study also utilized college students who reported on pacifier use and completed a scale designed to assess emotional intelligence.
In the first study, pacifier use was related to reduced facial mimicry in boys but not girls. In the second study, reduced perspective taking was found in males who reported past pacifier use. In the third study, reduced emotional intelligence was found for males but not females who used pacifiers in childhood, as was trait anxiety.
The authors concluded that the evidence supported their hypothesis that pacifier use could be detrimental to emotional development in boys. They further suggested, based on some of their analyses, that this effect of pacifier use was most important when they were used during the day. The researchers concede that their study design, however, could not determine causality with confidence.
In my view,this article unfortunately falls into the classic trap of many studies that assess an environmental variable and a behavioral outcome and then suggest causality between the two without really an ability to do so. Without measuring behavior in infancy, it seems quite likely that a third variable, like a more irritable temperament, is likely related BOTH to increased pacifier use and later difficulties with emotional development. Indeed, it seems quite plausible that the direction of causality is backwards from the direction the authors suggest with emotional difficulties related to increase pacifier use rather than the other way around. Another pet peeve of mine in this study is that the axes on their graphs do not include zero and so the findings related to pacifier use look much larger than they are. What is puzzling, however, is why such findings then would be found in boys but not girls.
It may well be advisable not to overdo pacifier use, but overall, I would consider these results to be highly preliminary at best.
Niedenthal PM, et al. Negative relations between pacifier use and emotional competence. Basic and Applied Social Psychology 34:387-394, 2012.