Health economist Dr. Frederick Zimmerman helped run the study that asked whether baby DVDs actually built babies' language, and this article looks at what his team found, what it could and could not prove, and what genuinely grows vocabulary before the age of two.
Dr. Frederick Zimmerman is a health economist at the UCLA Fielding School of Public Health. That job title matters. An economist's training is, at bottom, a discipline of scepticism about claims: when a product promises a benefit, the instinct is to ask whether the benefit shows up when you measure it, and what a family really gets for the time and money spent. In the mid-2000s, the claim in front of him was a big one. An entire industry had grown up around videos marketed to the parents of babies, promising, implicitly and sometimes explicitly, that watching them would make infants brighter, more verbal, more ready for the world.
Zimmerman did not investigate that promise alone. He worked with the paediatrician Dimitri Christakis and the developmental scientist Andrew Meltzoff, an unusual spread of expertise: a clinician who studied children's media exposure, a researcher who studied how infants learn, and an economist who knew how to interrogate outcomes in survey data. Together they produced one of the landmark pieces of baby media research, built on the plainest question imaginable. Do babies who watch more of this material know more words?
The study was published in the Journal of Pediatrics in 2007. The team surveyed families of children aged 8 to 16 months and looked at the relationship between what those babies watched and the vocabulary they understood. The result ran directly against the marketing. Each hour per day of baby DVD viewing was associated with significantly fewer vocabulary words understood. Read that again slowly, because the direction is the whole story: not a smaller benefit than promised, not no effect, but an association pointing the wrong way. The products sold on the promise of making babies smarter were the ones associated with knowing fewer words.
The source
Zimmerman, Christakis & Meltzoff (2007), Associations between Media Viewing and Language Development in Children Under Age 2 Years, Journal of Pediatrics · Read the original
The same dataset offered a quiet counterpoint that is easy to miss in the noise the headline finding generated. Reading to a baby and telling them stories showed positive associations with vocabulary. The activities that cost nothing, require no equipment and have been practised by parents for as long as there have been parents were the ones that travelled with knowing more words. The 2007 paper is therefore not really an anti-screen document. It is a comparison of two ways an infant can spend the same half hour, and a report on which one kept company with language growth.
Now the honest part, which any careful reader owes this study. The data are associational. A survey of families cannot prove that the DVDs caused the smaller vocabularies; it can only show that heavy viewing and fewer words were found together. Perhaps families reached for the videos for reasons connected to language in other ways. The findings were also contested, vigorously, by the industry whose products were implicated. But here is what changed and never changed back: the burden of proof flipped. Before 2007, baby media was sold on an assumed benefit. After 2007, the makers needed to demonstrate that benefit, and the demonstration never arrived. A product can survive an unproven harm. A product sold entirely on a benefit cannot easily survive an unproven benefit.
For a parent, the first implication is liberating rather than alarming. You can stop paying, in money or in hope, for screen products that promise to build your baby's brain. The best evidence on the flagship category found an association running in the opposite direction, and nothing since has rescued the original promise. If a video keeps a baby calm while you cook, that is a babysitting decision a parent may make with open eyes. It is not an educational investment, and skipping it denies your child nothing.
The second implication is where the real action is. Language before the age of two grows in the back-and-forth between a baby and a person who loves them. The positive associations in Zimmerman's data belonged to reading and storytelling: a voice, a face, a shared point of attention, a pause that waits for the baby's response. A screen cannot wait. A parent can. The practical question is not how to find a smarter video but how to fill ordinary minutes with words aimed at this particular child, about the thing this particular child is looking at, right now.
The third implication is about guilt. If your baby has watched these videos, the associational evidence cuts both ways: it cannot promise harm any more than it could promise benefit. Vocabulary at 16 months is not destiny, and the inputs that matter most, talk, books, play, are available in unlimited supply from today.
Here is what the winning side of Zimmerman's comparison looks like in a real kitchen. A baby of fourteen months sits on the floor with a wooden ark, tipping the animals out with both hands. Each one is a word waiting to be handed over. The parent, half-watching from the table, names them as they surface: elephant, as the heavy little body thuds onto the boards; lion; two giraffes, look, they match. The baby holds the elephant up. The parent says elephant again, and again the next morning, and weeks later the word arrives in the baby's own mouth, blurry and triumphant. No video can do this, because no video knows what the baby is holding. The engine of early vocabulary is the word landing on the exact thing the child is attending to, at the exact moment of attention.
This is narrated play, and it asks almost nothing of a tired adult. You do not teach; you commentate. The block goes on the tower, the tower wobbles, the parent says wobble in the tone the moment deserves, and the word is welded to the feeling. Solid, graspable toys are unusually good scaffolding for it because they hold still while a sentence happens, and because their textures and weights give you so much to say. A basket of traditional wooden toys made for naming, stacking and handing back and forth → is, in this sense, a vocabulary kit: every animal, block and ring is a noun with a handle on it.
At Jaques London we have been making playthings on this principle since 1795, longer than any other games company in the world, and a century and a half before anyone tried to sell a parent a smarter baby. The ark and its named animals, the shape that finally drops through the right hole, the book read for the ninth consecutive evening: these run at the speed of a conversation, which is the speed at which language is built. Our educational toys designed for shared, talked-over play → earn that word the only way it can honestly be earned with an infant: by giving an adult and a child something to talk about together.
The original study, Associations between Media Viewing and Language Development in Children Under Age 2 Years, is worth reading for how plainly it states both its findings and its limits. To see where it sits in the wider evidence, start with our guide to the science of play and screens, then our age-by-age screen time guide for what the research suggests at each stage, and our piece on why real play matters for the positive half of Zimmerman's comparison.
No, and the authors were careful on this point. The 2007 study was a survey, so it could show association, not causation: among families of 8 to 16 month olds, each daily hour of baby DVD viewing went with significantly fewer vocabulary words understood. What it did do, decisively, was strip away the assumption of benefit. The products were sold as language-builders, the data pointed the other way, and the promised benefit has never since been demonstrated.
Almost certainly not in any way that matters now. Associational findings describe patterns across many families, not verdicts on one child, and can no more promise harm than the marketing could promise benefit. Language development responds to what happens next: the same dataset associated reading and storytelling with knowing more words, and both are available to you tonight, free.
The activities that showed positive associations in Zimmerman's data: reading to your baby and telling them stories. In practice the common thread is responsive talk, words aimed at the thing your child is attending to at that moment. Naming the animals they are holding, narrating the tower they are stacking and reading the same book on repeat all do this naturally. The repetition that bores you is precisely what a learning brain wants.
The technology is different; the claim made to parents is often identical, and it carries the burden of proof that flipped in 2007. Treat any product promising a smarter baby as unproven until shown otherwise, because the flagship category, when finally measured, was associated with fewer words rather than more. The well-evidenced route to early language remains a person, a shared focus and a running supply of words.
Britain's oldest toy maker. Every toy open-ended, wooden, and built for exactly the kind of play the research recommends.