Overhearable speech (speech that may occur when caregivers are talking to each other in the child’s presence), constitutes over half of children’s language exposure, but its role in language development remains underexplored. Researchers from the University of Chicago, The New School for Social Research and Princeton University examined when and how English-learning children growing up in the United States understand words that they overheard from their parents’ conversations at home.
The present study focused on word learning and researchers compared children’s recognition of words that parents reported as primarily overhearable to children (i.e., “high-overheardness” words associated with adult talk such as pot, salad, and charger) with words that parents reported as primarily directed to children (i.e., “low-overheardness” words such as zipper, mirror and oatmeal). The study included 79 predominantly White and mixed-race U.S English-learning children that were assessed at 18, 24 and 30 months via parent reported surveys of their children’s recognition of household objects.
The findings show that 24- and 30-month-olds could recognize high-overheardness words and 18-month-olds were not able to recognize these words. However, 18-month-olds with larger vocabularies by 24 months showed better recognition of high-overheardness words and a smaller recognition gap between high- and low-overheardness words than peers with smaller vocabularies. This suggests that early world learning is dynamic and changes alongside children’s developing language abilities and social experiences.
The research is featured in a new Child Development article “Developmental change in acquiring overhearable words from naturalistic contexts” by Yuchen Jin (University of Chicago), Ruthe Foushee (The New School for Social Research), Kennedy Casey (Princeton University) and Marisa Casillas (University of Chicago).
The Society for Research in Child Development (SRCD ) had the opportunity to speak with the author team to learn more about the research.
SRCD: Did anything in the results surprise you?
Author team: Yes, one finding genuinely surprised us. We had expected that children as young as 18 months would already recognize high-overheardness words. After all, by this age, toddlers have already demonstrated several skills needed to learn from overheard speech — things like following an adult's gaze, tracking conversations between other people, and picking up new words without being directly addressed. And in fact, lab experiments had already shown that 18-month-olds can learn novel words through overhearing. But that's not what we found. In our study, the 18-month-olds did not reliably recognize the high-overheardness words. Only the 24- and 30-month-olds did. Why would that be? One most likely explanation is that natural overheard speech presents a tougher challenge than the overheard speech researchers create in experiments. In the lab, everything is carefully controlled to give children the best shot at learning: the target word is clearly labeled, the object is visible, and the setup is designed to hold their attention. But at home, overheard speech is messier. It doesn't come with the exaggerated, sing-song tone adults use when talking to babies, for instance. In a lab study, researchers typically keep all these factors the same across the two conditions — directed and overheard — so they can isolate just one thing: the effect of being an addressee versus an overhearer. That's a powerful approach, and those studies taught us something important. But they also created a kind of best-case scenario that doesn't fully reflect what children face at home. Meanwhile, our study aims to show what children actually do in the chaos of everyday. The two pictures don't line up as neatly as we might have assumed. And this is exactly why we need both kinds of research.
SRCD: What does this teach us about language development in toddlers?
Author team: Toddlers are not just learning what we deliberately teach them — they are also quietly absorbing the conversations happening around them. They are linguistic opportunists. They first learn from the speech we offer them directly; then, somewhere around their second birthday, they start helping themselves to the conversations we never meant for them to hear. This shift matters. Adult conversations are full of words that simply don't come up when we talk to a one-year-old — words like "wallet," "receipt," or "appointment." These are the building blocks of adult discourse, and overhearing may be one of the main routes through which children acquire them. In that sense, learning from ambient talk is not just about vocabulary size; it's also about how children are gradually socialized into the adult world and eventually, to talk as adults do. Moreover, children vary from each other. Some are picking up words from overhearable speech earlier than others, and that early ability seems linked to having a bigger vocabulary overall. It may be a virtuous cycle: more known words help you learn more words from harder sources, which in turn grows your vocabulary further.
SRCD: Can you explain how this research might help parents/caregivers, daycares/child development centers and researchers?
Author team: For parents and caregivers, on the one hand, it is clear that talking directly to your child matters in the earliest stages. On the other hand, the current study offers additional insight — you don't need to worry too much about shielding your child from adult conversation. The ambient talk around them isn't noise. Rather, it's a resource. By age two, children are actively mining those conversations for new words, and the richer that language environment, the more raw material they have to work with. That said, it may be worth being mindful of what you say in front of your child, even when you assume they're not listening or can't yet understand. Facilitating language development isn't just about what we deliberately teach — it's also about the linguistic environment we create around them. For daycares and child development centers, one practical implication is the value of mixed-age groupings. When younger children can observe and even participate in older children's activities, they're exposed to more complex speech that sits somewhere between baby talk and full adult conversation. This could be a natural, low-cost way to support both vocabulary growth and the gradual shift toward more adult-like language use. For researchers, the study points to a gap that deserves more attention. Lab experiments have shown us what children can do under ideal conditions, but we still know relatively little about how word learning actually unfolds in everyday life, especially when it comes to overhearable speech. Future work that combines naturalistic observation with controlled methods could help us build a more complete picture of how children piece together their vocabulary from the full range of input available to them.
SRCD: What are some of the research limitations?
Author team: There are a few important limitations to keep in mind. First, we can't say for certain that children learned the high-overheardness words through overhearing. It's worth drawing a distinction here: "learning via overhearing" refers to the actual process that the children figure out a word by listening in on others. "Learning high-overheardness words" refers to the outcome that children acquire words characteristic of adult discourse. Our study is about the outcome; we can't definitively claim the process behind it. Second, we relied on parents' reports to estimate how often children heard each word in directed versus overheard speech. Parents have a pretty good sense of these patterns, but their estimates are still subjective and may not perfectly match children’s actual experience. Lastly, the sample of US learners in our study is relatively educated and wealthy. We don't yet know whether the same developmental timeline would hold for children from different socioeconomic backgrounds.
SRCD: What do you recommend for future research in this area?
Author team: I think there are three directions that are particularly valuable to help us better understand how children learn language through overhearing. The first is better documentation of what children's overhearable input actually looks like in everyday life. We know it's abundant, but we have surprisingly few detailed records of it. Second, we should look beyond vocabulary to identify other areas where overheard speech might make a unique contribution. For example, overhearing conversations between adults might teach children something about conversational structure or social norms that child-direct speech alone doesn't provide. Third, cross-cultural work is essential to examine the universality and specificity of language learning through overhearing. In communities where young children are less often the center of adult interactions — as has been documented in some Mayan and Papuan communities, for instance — children may rely on overheard speech earlier and more heavily. More broadly, we are also excited about bigger questions behind the scenes: what do children gain from occupying different roles in conversation — not just as the person being spoken to, but as a third-party observer? Each of these roles probably offers a different window into how language works, and we’re still on the way to understand what children take away from them.
This research was supported by the First Year Scholar Summer Research Grant from the Social Sciences Division at the University of Chicago and the Gianinno Graduate Research Award from the Department of Comparative Human Development at the University of Chicago.
Summarized from an article in Child Development “Developmental change in acquiring overhearable words from naturalistic contexts” by Jin, Y. (University of Chicago), Foushee, R. (The New School for Social Research), Casey, K. (Princeton University) and Casillas, M. (University of Chicago). Copyright 2026 The Society for Research in Child Development. All rights reserved.
Child Development
Observational study
People
Developmental change in acquiring overhearable words from naturalistic contexts
22-Sep-2026