STUDY ANALYSIS: Pacifier Use Linked to Reduced Vocabulary in Infants

And I think I know why

In my daily rounds as I browsed a new batch of scientific research, I came across a report about a study that links pacifier use to reductions in vocabulary in infants. Basically, the longer a child has a pacifier stuffed in its gob, the smaller its vocabulary by a certain age.

On the face of it, you can imagine why that might be the case. It could simply be that, instead of vocalising and engaging in the kinds of rough mimicry that eventually become fully formed speech, kids with pacifiers just sit there—pacified. I mean, that’s the point of the device in the first place, as any adult with a brain will know.

I suspect there’s more to it than that, though.

Here’s how the study was carried out.

For their study, the researchers recruited parents of infants from Oslo, Norway, through birth registries, covering the period from 2019 to 2020. Initially, the study included 1,630 participants, but after applying specific inclusion criteria, such as monolingual exposure to Norwegian, being born full-term, and having no reported visual, auditory, or cognitive impairments, the final sample consisted of 1,187 infants.

To assess vocabulary size, parents completed an online questionnaire that included the Norwegian versions of the Communicative Development Inventories (CDIs). For 12-month-old infants, the CDIs measured both vocabulary comprehension and production, while for 24-month-olds, it measured vocabulary production only. Comprehension refers to the ability of infants to understand and recognize words when they hear them, while production refers to the ability to actively use words in speech.

Parents also provided detailed reports of their child’s daytime pacifier use. They retrospectively estimated the average daily use in whole hours for two-month intervals from birth until the assessment date. This allowed the researchers to calculate the total hours of pacifier use over the infants’ lifetimes, referred to as Lifespan Pacifier Use (LPU).

The study itself doesn’t draw any conclusions about why pacifier use might have these effects; although it does suggest that later use (i.e. at 24 months rather than 12) is linked to a much greater reduction in vocabulary, which could mean that a specific process that takes place around that time is being retarded. Between 12 and 24 months of age, most children progress from the so-called “babbling” stage to the one- and two-word stages, where they start to acquire individual words, and between 24 and 30 months they enter the “telegraphic stage,” where they start putting words to express ideas, but in an ungrammatical fashion (like a telegram).

My guess is that there is likely to be a chemical component to this link as well. After all, pacifiers are often made of plastic, and we know that plastic chemicals are implicated in pretty much every single one of the prevailing maladies of our age, from reproductive and fertility problems, to obesity, diabetes, heart disease, cancer and neurodegenerative diseases like Alzheimer’s and Parkinson’s. It’s one of the things I talk and write about most frequently, as you’re probably well aware.

There’s ample evidence linking phthalate exposure to impaired brain development in children. Pre-natal exposure to phthalates (i.e. in the womb) appears to have significant negative effects on children’s brains, but it’s likely that these neurotoxic effects are still present after children are born and persist throughout a child’s development, until adulthood.

And it’s not just phthalates either. Other ubiquitous plastic chemicals, like bisphenol A (BPA) appear to have the same effects.