Magdalena Rychlowska and her colleagues claim that because dummies obscure babies' faces, they interfere with the way that adults respond to babies' emotions.
The researchers used electrodes to record the facial muscles of 29 women (average age 21; two of them were mothers) while they looked at photographs of two young babies expressing happiness, sadness, anger or a neutral emotion. Sometimes the babies had dummies in their mouths; other times didn't. Also, some of the photos featured a white square superimposed over the baby's mouth region. This last condition was to control for any influence of the sight of a dummy, beyond its obscuring effect. As well as having their facial activity recorded, the participants also rated the intensity of the emotions shown by the babies.
When the women looked at happy babies with a dummy in their mouth (or when a white square was superimposed over the babies' mouth region) they exhibited less activity in their Zygomaticus muscle, which pulls the mouth into a smile. In other words, they showed less mirroring of the babies' happiness. When the babies had a dummy, or a white square covered their mouth region, the women also rated the babies' happiness to be less intense. The presence of a dummy was no more interfering than the white square, which suggests the effect of the dummy was purely due to its visually obscuring effect, not to any cultural or emotional assumptions the women may have made.
What about when the babies expressed sadness and anger? The women's corrugator frowning muscles were just as active when they looked at sad and angry babies whether the babies had a dummy or not, and irrespective of the presence of a white square. However, the women rated the babies' sadness as less intense when the babies had a dummy or when a white square was superimposed over their mouth area.
The researchers said their results are important because they show how the use of babies' dummies can interfere with emotional resonance between adult and baby. "Resonance with adult perceivers allows to infants to gain emotional understanding and develop mentalizing abilities," they said. They also noted: "...[P]erceivers may find interactions with infants using a pacifier less enjoyable and less stimulating." The new results also build on past research by the same team, which found amount of dummy use in infancy was associated (in boys only) with less automatic facial mimicry at age 6 to 7. Bear in mind though, that this past research did not prove dummy use was responsible for the later reductions in mimicry.
There are some obvious problems with this new study - most obviously the reliance on static photographic stimuli, and also the fact that the research didn't involve mothers or fathers interacting with their own offspring. It's also worth highlighting that the use of infant dummies has been associated with positive outcomes, most notably reduced risk of sudden infant death when used during sleep. Some parents might also counter the current findings with the argument that, by soothing their babies' distress, strategic use of dummies actually has emotional benefits for their babies.
Rychlowska, M., Korb, S., Brauer, M., Droit-Volet, S., Augustinova, M., Zinner, L., & Niedenthal, P. (2014). Pacifiers Disrupt Adults’ Responses to Infants’ Emotions Basic and Applied Social Psychology, 36 (4), 299-308 DOI: 10.1080/01973533.2014.915217
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Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.