These moments of connection are sweet, emotional encounters, but researchers know they are much more. Research scientists at the University of Washington’s (I-LABS) recognize this “social ensemble” as the nascent that lay down the pathway to language — the gateway to connection, education and the world of ideas. Given that these distinctive interactions appear to be universal and uniquely human, I-LABS researchers wondered what their developmental purpose could be. What they found was not only that the babies’ brains “lit up” during these interactions, but that the degree to which individual babies responded to social interactions predicted the child’s language growth beyond 2-½ years of age.

“What we were trying to see is whether that social ensemble — the parentese, the warm smiles, the touches, and the back and forth that says you’re paying attention — has a (developmental) goal in addition to the emotion that’s connecting these two people,” says Dr. Patricia Kuhl, I-LABS’ co-director, and holder of the Bezos Family Foundation Endowed Chair in Early Childhood Learning, who led a groundbreaking longitudinal study linking infants’ individual brain responses to social interactions and their future language development.

Using a magnetoencephalography () brain-imaging device — a safe, silent, noninvasive technique I-LABS has tailored for studying infants — the researchers monitored the brains of a group of 5-month-old infants during social and nonsocial interactions with an adult. The researchers then followed up with the children at 18, 21, 24, 27 and 30 months. Their findings were published in the April issue of and represent the first such study to track the relationship between infants’ social responses and their language acquisition.

Arriving Ready for Language

Even before they produce their first words, infants are learning phonetic sound patterns. They come into the world able to pick out the human sounds that make up words in any language. Previous independent studies have shown that there is a “sensitive period” for phonetic learning between 6 months and one year when these initial universal phonetic capacities narrow down and become specific to their native languages.

“Testing the babies at 5 months was important because we were trying to establish that this social connection that lights up the baby’s brain and gets them ready to learn comes first and sets them up for when this sensitive period begins,” says Kuhl, the study’s lead author. “The social interaction is of cognitive importance and gets the baby ready for what’s coming around six months. The exaggerated face and silly-sounding speech (the ‘ensemble’) come intuitively and are the original ‘hook’ that pulls them and primes them for the learning to come.”

For the study, Kuhl says, researchers set the infants up in the MEG device and an adult female researcher engaged with the baby, speaking in parentese and reacting warmly back and forth using the tried-and-true adult-baby call and response. For the experiment’s nonsocial control, the researcher would then turn and speak to another adult seated just out of the infant’s view. The intention was to capture typical social interactions that babies experience regularly in their home environments.

The researchers’ findings showed that at 5 months, face-to-face social verbal interaction between an infant and an adult who’s sensitive to the baby’s cues significantly increases the child’s brain activity in regions involved with attention, compared with a nonsocial control. Even more exciting to those interested in babies’ language learning, the scientists found that babies’ individual levels of brain activity during the social interactions showed a strong positive association with their subsequent language skills.

“Not all children’s brains lit up to the same degree to the social ensemble,” Kuhl says. “Their social attention is different. The ones with more social attention learned language faster.”

The Joy of Face-to-Face

Kuhl says the researchers knew from previous studies that social interaction — rather than, say, watching a video or app — is essential for language learning. The current study shows that parents’ natural use of parentese, coupled with smiles, touch and their warm volley and return captures infants’ attention at an early age and makes them ready to latch onto language when that sensitive window opens around 6 months.

The researchers didn’t use the children’s parents in this study because they were concerned their history of interaction might color the babies’ responses, nor did they have the researcher turn from the baby to use a smartphone or device because they have seen in other research how upsetting that is to the babies. The researcher interacting with the babies had not met them before the experiment began but started the kind of natural interaction with them that might occur in the grocery store or when other adults drop over for a visit. She cooed back and forth with the baby, then, on cue, looked away to interact with another researcher “offstage” for a moment. On another cue, she turned back to the baby and began the social interaction again.

The babies’ little brains loved all that attention and weren’t happy (as observed by MEG’s neural light show) when they were being ignored. Some babies’ brains really sparked at the social interaction and those were the babies who, by 2-½ years, showed the greater vocabularies and more sophisticated use of language.

This doesn’t mean that babies have to be attended to at all times or they’re going to lose out on language skills, Kuhl is clear to state. No helicopter parenting here!

“That would be the wrong message to take from this research,” she says. “Part of these interactions’ special nature is that they only come occasionally. The interaction is there, then it goes away, and next time it comes, it’s like Christmas — something to be anticipated and excited about. So, parents shouldn’t stress and think, ‘Oh my gosh, here’s one more thing I have to think to do.’ Its magic is that it’s unexpected and babies are overjoyed by that.”

More Questions, More Studies

As good studies do, this one has prompted almost as many questions as it’s answered. For one thing, researchers want to know about what’s happening with the brains of babies whose mothers are dealing with clinical depression.

“In mothers who have clinical depression, you don’t see the smiles, the parentese and the warm interactions,” Kuhl says. “There are all kinds of issues with these children, one of which is a depressed affect and a slow growth of language.”

The current study also points to a greater understanding of autism and draws attention to other research, such as that of Dr. Karen Pierce of t he University of California San Diego, et al, showing that babies’ reduced attention to parentese can both contribute to downstream language and social challenges, and help diagnose toddlers with autism spectrum disorder.

“When (Pierce) tests young children who are at risk for autism (because they have a sibling with autism) with a social versus nonsocial stimulus — such as people interacting versus cars or just sound — the children with autism tend not to like social, people-oriented stuff,” Kuhl says. “And the more they tend not to, the more severe their clinical symptoms for autism are.”

Another fascinating study in the I-LABS pipeline is the differences between mothers and fathers in their deployment of parentese. Preliminary research indicates that men are talking to their babies only 25 percent of the time, compared with mothers. They do use the social ensemble to interact with babies, but ongoing research is looking at whether fathers stop using parentese earlier in the child’s development, and if they do, why that may be the case.

°Âłó˛šłŮ’s that about? We’ll have to stay tuned.

Meanwhile, we can go ahead and indulge our impulse to engage in that silly social way with babies and know that we aren’t just forming emotional connections; we’re helping open their pathway to life with other humans.

“I suppose if you were on an island by yourself and had all the survival skills you needed to discover food, water and shelter, you might be able to survive as an isolate,” Kuhl says. “But everything we know about human beings is that we inherently crave connection with each other. And language is the gateway to any communicative connection we have. It’s our social-emotional glue.”

Both research teams used the nonprofit LENA’s to glean their findings. The wearable device delivers detailed information on what children hear throughout the day. It measures the number of words spoken near the child in addition to the child’s own language-related vocalizations.

It also counts child-adult interactions, called “conversational turns,” which both research groups say are critical to language acquisition.

“It is the conversational turns that drive brain development,” said Brown’s Sean Deoni, adding he’s concerned for the long-term success of children born after the pandemic began. 

The joint finding is the latest of discovered when researchers compared babies born before and after COVID. 

Deoni is principal investigator at Brown’s Advanced Baby Imaging Lab. He and other staffers there first spotted the problem when they noticed that children who visited the lab after March 2020 took longer to complete cognitive tasks.

“They were not as attentive, or at least not performing as well as we normally have seen,” Deoni said. It was this change that prompted him to take a new look at various data points gathered from the nearly 800 children his facility has worked with in recent years. After examining their neuroimaging and neurocognitive results, he and his team found child motor and language scores decreased sharply in 2021 and 2022, prompting them to search for an explanation for the decline.

The inquiry led them to analyze information gathered from children ages 12 and 16 months who were born before 2019 — well before the COVID outbreak — and after July 2020, months into its spread. The results showed a major drop in verbal functioning between the two groups. Those born after COVID demonstrated slower verbal growth over time.

Tests showed, too, these babies experienced a significantly slower rate of white matter development versus the children from studies done before the pandemic.

“White matter is basically the wiring of the brain,” Deoni said. “It’s what carries information throughout the brain and to different cortical regions where it is processed. White matter damage, for example, is a hallmark of multiple sclerosis. Reduced white matter development is associated with reduced cognitive development.”

Deoni and his team also found a significant drop in adult words per hour and conversational turns between the two groups of children. The deficit will have a significant impact on kids he said, citing his own group’s earlier research. 

Neither research team focused on the cause of the drop in caregiver interactions with babies, only the outcome, though Deoni cited the heightened stress, depression and burnout associated with the pandemic as possible explanations. 

Jill Gilkerson, a linguist specializing in early language acquisition and LENA’s chief research and evaluation officer, said the reasons might differ from one household to the next. 

“I don’t think we are going to be able to find a single cause to point to, and I’m not sure that we need to,” she said. “We hope this data validates concerns caregivers may be having, helps them know they are not alone in those feelings and furthers the conversation about the need to invest in support for families at every level.”

LENA’s study showed child vocalizations dropped significantly across all groups of children, but particularly among those from the lowest socioeconomic level. The frequency of caregiver/child conversations also decreased dramatically, particularly among children from the poorest families, it found.

“It’s often the case that when these adverse events happen, it’s those who are already the most vulnerable that are hit the hardest… and I think that we are seeing this here,” Gilkerson said.

The connection between economic security and language acquisition was very much a pre-pandemic concern as well. A found that children growing up in low-income households hear 30 million fewer words than their peers from high-income backgrounds. A 2018 study raised questions about the extent of the gap, but the science is clear that children’s first three years are the most critical time for brain development.

LENA, based in Boulder, Colorado and founded in 2004, aims to improve children’s futures through early talk technology and data-driven programs. Its software measures a child’s language environment and provides feedback to parents and professionals vested in preparing them for school.

Its study of 136 COVID-era babies included only those who started gestating on or after the start of the pandemic in mid-March 2020: All were born after December 15 of that year. The findings from this group were compared to a pre-COVID pool, which captured recordings between 2017 and March 2020 and included 494 kids.

These language deficits, once shared with caregivers, are possible to correct. But, Gilkerson said, it’s important for groups like hers to suggest practical, easily applicable solutions.

“We need to … provide parents with strategies for integrating talk — interactive talk, quality talk — with their children during their regular routine,” she said, rather than add a new task to their already stress-filled lives.

LENA’s latest research builds off earlier findings the group published in the journal in October 2018: That study showed early talk and interaction, particularly for children ages 18 to 24 months, can predict school-age language and cognitive outcomes. In that paper, LENA examined day-long audio recordings for 146 infants and toddlers completed monthly for six months.

LENA’s Language Environment Analysis software measured the total number of adult words and adult-child conversations. LENA conducted follow-up evaluations at 9 to 14 years of age. It concluded that adult-child conversations influence a child’s IQ, verbal comprehension and vocabulary scores 10 years later.

And while it’s true, both researchers acknowledged, that children are resilient, recent data does not yet reflect the bounceback from the pandemic.

“We are not seeing them hit a floor and all progressively get better,” Deoni said. “We are seeing them continue this downward trend.”

And it’s not just a language acquisition problem. Reduced verbal development is being driven by poor motor development, Deoni said: This early foundational skill could have a lasting impact on children, one that can be hard to correct for as they age.

“I’m worried about how we set things up going forward such that our early childhood teachers and early childhood interventionalists are prepared for what is potentially a set of children who maybe aren’t performing as we expect them to,” he said.

To be clear, the baby talk we’re discussing is not of the goo-goo, gah-gah sort of speech. Infant-directed speech is the high-pitched, singsong, slowed-down way adults talk to babies that sets the stage for vocabulary-building conversational turns — Is that your hand? Look at that hand! And five little fingers! Most adults automatically fall into this exaggerated cadence and register of speech when they come face to face with a baby.

To discover their preference for infant-directed speech, a unique study of hundreds of babies involving 17 labs on four continents compared babies from bilingual backgrounds to babies from monolingual backgrounds, and exposed them to many different language combinations. According to primary investigator Dr. Krista Byers-Heinlein, associate professor of psychology at Montreal’s Concordia University, each baby was played short recordings of English-speaking mothers using both infant-directed and adult-directed speech. The global nature of the study ensured that many different language combinations were represented.

Regardless of their native language, the babies responded more to the recordings of infant-directed speech, or baby talk, than to the adult-directed speech. All the babies preferred the baby talk samples, which in this study were recorded in English, over adult-directed speech, but babies from homes in which English was spoken really liked it. In baby research, Byers-Heinlein says, looking indicates listening, and when the babies who came from homes in which English was spoken heard the recordings by English-speaking moms, they really perked up.

“The more familiar they were with the language, the better they liked that infant-directed speech,” Byers-Heinlein says. “A baby who was hearing English 75% of the time in their home would show a greater preference than a baby who was hearing English 25% of the time.” The researchers were not testing the babies’ preference for English, but whether the infants were especially tuned in to infant-directed speech. The fact that the babies whose native language was English showed a marked preference for the English baby talk points to how exquisitely babies are listening and picking up on the languages they hear in their environment.

“We think that interest is the foundation of language acquisition,” she says. “They hear it and think, ‘Oh, this is something for me. I should pay attention here.’ They’re paying attention to all the human speech they hear, but they really respond to the baby talk directed at them, and we think these adaptations help the learning process for them.”

One of the hallmarks of infant-directed speech is that it is repetitive, she says. Look at the ball. Look at the ball. Do you see the ball? Babies are keenly attuned to repetition and the really close repetitions in infant-directed speech appear to help them start unlocking the sound, the words and the grammar they need to figure out language. Infants are more able to focus more efficiently and distinguish one word from another in the slowed-down cadences of infant-directed speech. Some studies have shown that babies learn words more effectively and demonstrate better long-term memory for words spoken in infant-directed speech.

Previous studies of the use of infant-directed speech have been primarily conducted in North America on monolingual babies. What distinguishes this research from other studies is the large-scale, multi-site study on bilingual infants. The project tested 333 bilingual babies and 384 monolingual infants in two age groups: 6 to 9 months and 12 to 15 months.

Knowing more about bilingual babies is essential, Byers-Heinlein says, because the number of bilingual families in both the U.S. and Canada continues to rise. According to the Annie E. Casey Foundation, nearly 14 million U.S. kids speak a language other than English at home. In California, 44% of children grow up in bilingual homes. The latest Canadian census has the number of bilingual residents at 18%, the highest on record.

The study arose as part of a remarkable research collaboration, , a project that brings researchers together to address challenging questions about the nature of early development and how it’s studied.

The ManyBabies project is conducted globally with Open Science at its core. The United Nations Educational, Scientific and Cultural Organization (UNESCO) describes Open Science as “a methodology that allows scientific information, data and outputs to be more widely accessible and reliably harnessed with the active engagement of all the stakeholders.” It encourages science to be more connected to societal needs and promotes equal opportunities for scientists, policymakers and citizens, making it a game-changer in bridging the science, technology and innovation gaps among and within countries.

According to UNESCO, the Open Science movement has spread rapidly across nations since its inception and its call for the “opening of the gates of knowledge” to accelerate the achievement of scientific solutions for global challenges.

According to Byers-Heinlein, “ManyBabies is the most exciting thing I’ve been involved with in my career. I can’t believe this is a thing that is actually happening.

“Infant research has a number of problems,” she says, “one of them being that our samples are so small. How many babies can I actually test in my lab? Just finding the babies, bringing them in, convincing the parents to take part in the study and then, half the babies don’t complete the study because they cry, or they get bored or they just don’t want to. I mean, they’re babies, right? They’re just hard to study — and especially if you consider how precise you need to be when you think of infants. A baby of 12 months is very different from an 18-month-old.

“So, imagine if you want to study adults, but you only want to recruit adults who are 52 years and one month old. That’s a little nuts. But with babies, that’s how precise you need to be.

“And because of the way science works, the research has been very fragmented. I do things in my lab; you do things in your lab and maybe we publish something and talk about it at a conference. But how do we make real progress on these things and get the kind of samples we need?”

The answer, through Open Science, is that the researchers put their heads together and start creating collaborative projects like ManyBabies. Byers-Heinlein compares it to the way scientists in other fields do their work; for example, particle physicists who don’t each have their own particle accelerator but plan the science together, collaborate and make progress in particle physics that none would have been able to accomplish on their own.

“ManyBabies was born as a way for all these infant researchers to work together,” she says. “First it was a few researchers talking to each other, then emails back and forth and people began to get really excited about the idea of planning a study together, then each tests the babies in our own labs. Our normal sample size might be 16 babies or maybe 32 babies. But now, we have studies involving hundreds of babies from around the world.”

The study on bilingual babies is one of the first to come out of the ManyBabies project, and Byers-Heinlein says the collaboration is just getting started.

“It’s really unprecedented,” she says. “Think about coordinating across 69 labs and studying thousands of babies. It’s an incredible movement to work together and it’s opened up many more possibilities for further study. It’s a very rich data set. And the data is all completely public — anyone can take a look at all the data. It’s very unusual, because often scientists are hesitant to share their data with other researchers.”

Here’s a look at some of the other fascinating  at ManyBabies. Meanwhile, be loud and proud when speaking to your infant in baby talk: It’s their love language, no matter what language you use.

For decades, a common belief has held that speaking more than one language in a child’s home confuses the child, makes it more difficult for them to learn English and might even hold them back in school and in life. The unfortunate consequence of this belief has been that some dual-language households have enforced an “English-only” rule around the children, leaving non-English speaking members of the family constrained and the child disconnected from some of the deepest and best of their heritage. Children may end up hearing less language overall if English is not a preferred language of adults in the household — at a time when their brains need language like their bodies need food.

In fact, the opposite is true. Researchers have found in numerous studies that bilingual babies learn English at the same rate as monolingual babies, with vocabularies that equal or exceed those of the English-only babies. Bilingual children have been found to have a more advanced ability to think about language and how it works, and there is some evidence that early exposure to a second language makes learning a third language easier.

Although the research is ongoing, multiple studies have found that juggling two languages from an early age actually enhances the mental skills and self-regulation referred to as “executive function,” which help people plan, solve problems and respond to the world around them in an orderly way. Some even indicate that being bilingual can offer protection decades later against age-related cognitive decline.

All over the world, as societies become more diverse and economies are globally connected, communities are working to create programs to introduce young children to learning a second language. Most are aimed at preschool children to kids in elementary school — a vast improvement on the traditional approach of starting young people on second languages in high school, but still a bit late.

According to Dr. Marley Jarvis, Outreach and Education Specialist at the University of Washington’s , researchers there have found it would make sense to start language learning much earlier: Babies’ brains are wired for language.

“I don’t want to say elementary school or later is too late for learning another language,” Jarvis says. “One of the remarkable discoveries about our brains in the past couple of decades is their plasticity and their ability to change. Everything we do every day is changing our brains. But learning language later doesn’t happen in the same way it does with very young children, so we’re working against ourselves by waiting so long.

“Children are already well-established in their first language before they even hit preschool.”

In fact, Jarvis says, research shows that babies begin to learn language sounds while still in the womb. By the time they’re born they distinguish their mother’s voice from ambient sound and are even able to .

Babies come into this world equipped with one of the most powerful computers known to humankind — already on task analyzing massive amounts of data on arrival. About 800 sounds make up all the languages of the world; each human language only uses 40 or so of those sounds. As babies lie in their little bassinets, they are not only absorbing the sights, sounds and sensual cues from this bright new world, is sorting through those multiple data streams like greased lightning, cracking the code of human language, sorting out which of those human sounds are useful in their environment. By the time they’re 10 months old, babies have “committed” to their native language, specializing in the language they hear around them, and the sounds and syntax of other human languages fade into the background.

In the case of a child surrounded by speakers of two or more languages, that commitment extends to those languages as well. As I-LABS co-director Dr. Patricia Kuhl, an international authority on early learning and brain development, observes in the video “Igniting Bilingual Learning,” babies’ language learning is time sensitive. The human brain will never be better at learning a second language than in the first three years of life.

Some parents fear that exposure to another language will limit the child’s English vocabulary, but researchers have also put that concern to rest with studies that show that bilingual children do not lag behind in the number of words they absorb. In fact, the vocabularies of bilingual children have been found to be than those of single-language children.

“In fact,” Jarvis says, “we have yet to see any evidence that a child is confused by more than two languages (though not all spoken at the same time). We haven’t seemed to find the limit. And they’re pretty good at knowing who is associated with which language. If you have a multilingual family, kids will naturally switch to the language appropriate to each person.”

And, she says, the sorting and switching from one language to another — code-switching — actually helps the baby’s brain become more agile and resourceful. As they sort through their data streams to find which language is being spoken and then respond appropriately, they begin to develop the impulse control and strategic thinking so essential to executive function. Structural brain studies indicate that bilingual adults have greater brain tissue density in areas related to language, memory and attention, with the highest levels of tissue density among those who were exposed to two languages before the age of 5 years.

Research scientist Dr. Naja Ferjan Ramírez, director of the University of Washington’s Language Development and Processing Lab, is Slovenian, married to a native Spanish-speaker, and their 4-year-old son easily switches among English, Slovenian and Spanish. Though he sometimes uses Slovene endings on English and Spanish words, he modulates his language to match the situation he finds himself in. He may throw in a Spanish or Slovene word in his English dialog, but this is because he has a bigger library to choose from. This code-switching is not haphazard, she writes, but adheres to the linguistic logic of the languages he’s using.

Each time he does, like a bodybuilder reaching for a heavier weight, he’s building his brainpower.

For anyone wanting to teach their small children another language, it’s important to remember that the learning takes place in interaction, not in mere exposure to a recitation of words. It’s the social brain, Jarvis says, that’s important in any kind of learning, especially in these early years.

In one , a group of University of Washington students went through an online training program and learned to tutor small children through playful, interactive learning. The students then were sent to Spain to deliver group English sessions daily with Spanish-speaking children in the Community of Madrid’s public infant education centers. The key practices in their training were to address the children often in English and to speak to the children in “parentese” (the higher-pitched, singsong language parents use to signal the child that this communication is for them). The learning context was highly social, with the tutors leading the children in games and activities that prompted face-to-face interaction. Tutors were trained to engage the children in frequent back-and-forth exchanges and to encourage the children to “talk” and interact with them. (I-LABS a series of research summaries with links to studies and practical family activities with tips for caregivers.)

Essentially, Jarvis says, the tutors played with the children in English in a highly social, engaging way for 45 minutes or so a day. The children in this study saw a nearly five-fold increase in their English speaking, compared with children in a control group in the school system’s English program. The children continued to develop in their native language, Spanish, at the same time. The big difference between the programs was the degree of social, back-and-forth, play-based interactions in the UW program.

If we want our children to meet the challenges of an increasingly diverse and global society, being fluent in more than one language will be an important element in that success. Parents who want their children to become the global citizens their brains are born to be can rest easy knowing that starting their children down that path as babies can only strengthen the child’s social and intellectual ability in the years to come.

“Conversation is not necessarily about having a rich verbal language,” says early learning scholar and author Dr. Kathy Hirsh-Pasek. “At first, conversation can be coos and gestures and funny noises. A baby’s language learning is about the connection, the back and forth communication that happens way before words. It’s like a duet: babies learn language through interaction. It’s never too early to start because they are always listening — even in the womb.”

A landmark study in 1995 reported on the “30-million-word gap” that divides higher income children from those in lower income families. The gap refers to the number of words spoken to children’s ears by the adults in their lives. The size of the gap correlates with significant differences in vocabulary, language development and reading comprehension. Since that revelation, some educators and parents have pushed hard to have babies start learning words — lots of words — as early as possible.

This creates what both Hirsh-Pasek and her long-time collaborator Dr. Roberta Michnick Golinkoff describe as a “flash-card” approach to language, which emphasizes the words themselves rather than the interactions that are the true delivery mechanism of language. This way of presenting isolated words without context is like dumping words on the baby and hoping some stick. The process resembles how some of us studied for the SAT, but how many of those words do we remember now?

Before they can learn vocabulary, the scholars say, babies have to learn to isolate or segment words from the stream of sounds that surround them. They do this in a variety of brilliant ways, from sorting out statistical cues connected with how frequently they hear a word to the stress patterns in the words swirling around them. “Juice? You want some juice?” By 6 months, babies recognize a novel word that follows their own name, but not a novel word after someone else’s name. Research shows that long before a child can produce words, they have stored the frequently heard word forms in their brilliant , ready for use when their vocal mechanism has developed enough to shape words.

At 24 months, the variability in babies’ vocabularies is breathtaking, ranging from 56 to 520 words, and these enormous differences, the scholars say, are rooted in both the verbal and nonverbal gestural interactions that take place between babies and their caregivers. The more of these back-and-forth interactions mothers and other caregivers have with their babies, the greater the child’s school-ready vocabulary by the time they’re off to kindergarten at 4½ or 5.

“The beautiful thing about that is that it doesn’t take anything fancy,” Hirsh-Pasek says. “It’s free. You don’t have to buy anything to have these kinds of conversations with your child. Babies learn words like spiders spin webs — it happens entirely naturally.

“But what you do need is be mindful of paying attention to your child. Because when you’re looking down at your cell phone and are locked into that, you ignore your child’s cues and questions and it breaks up the natural flow of conversation.”

Scientists refer to those back and forth interactions that start even before the baby can say a single word as “conversational turns” and studies show that the more conversational turns children experience, the greater the activation of a major language-processing area of the brain (Broca’s area), regardless of the child’s economic status or even the number of adult words they hear.

“What you’re going for isn’t just ‘volley and return,’” Hirsh-Pasek says. “It’s more like volley and return and return and return — responding to the child then responding to their response. One of my colleagues says you should ‘strive for five’ turns in the conversation.”

One of the most effective ways to engage in this back and forth, the experts say, is through the challenging quality of “wh-questions.” Like any good reporter, parents and caregivers need to master the fine art of “Who, what, when, where, how and why.”

Children respond more frequently and in more complex ways to wh-questions than to any other, Hirsh-Pasek says. “Start by looking where the child is looking,” she says. “Then, ask them about that — not one of those ‘close-ended’ questions that can only be answered with yes or no. You want the questions that encourage and build conversations (‘What is that?’ ‘I wonder what the doggies are saying?’), not the conversation crushers.”

Children who hear a lot of these questions that challenge their thinking are generally better able to understand and produce them as well. While harried parents might not always think the incessant “Why, why, why” of a toddler is a great thing, in the long run, those questions and the interactions they elicit can lead to richer vocabularies and concepts about the world.

Research shows that middle-class parents pose more questions to their children, on average, than parents from less resourced environments. However, there are many differences within families in both groups.  Further, fathers on average pose more wh-questions than mothers do. Toddlers in under-resourced environments are exposed to less verbal input than their middle-income peers, but since fathers across socioeconomic groups ask more of these “clarification” questions, researchers say they may play a unique role in supporting their children’s language and cognitive development. In one important study, African American fathers posed the most wh-questions of any of the groups regardless of income status.

The big bonus, scientists say, comes later in a child’s life when these challenging social interactions boost the complexity of their thinking and their verbal reasoning skills.

To develop a vocabulary, Golinkoff and Hirsh-Pasek say, children need to hear words embedded in sentences, and they need to hear different word types. They talk about this as the “architecture of language,” in which a child learns nouns as an entry point because they label concrete items, then moves on to verbs like “run” and “spatial-relational terms” — e.g., “bring the ball over here.”

When parents and caregivers take cues from the child and play off what the child finds interesting, vocabulary comes alive. When a child says, “°Âłó˛šłŮ’s that?” they aren’t asking simply to be told, “That’s a toaster.” They are asking for information on what the item is used for. Children need clear information about word meaning, Golinkoff says. To really know a word, the child has to have at least a minimal grasp of how that word might be used in different ways. They are hungry for context. “That’s a toaster. We use it to cook our bread sometimes, don’t we? It gets very hot. What else gets very hot?”

Though stacks of research make it abundantly clear that such natural interaction and playful learning serve as the platform for vocabulary learning, Golinkoff and Hirsh-Pasek say that the educational system is increasingly moving in the opposite direction, more toward the flashcards paradigm than playful interaction. Children can eventually learn definitions, they say, but passive memorization will never yield the depth and retention needed for a child to actually master vocabulary and the logical thought processes that turn language into the keys to the kingdom. How a child learns is as important as what they learn and what ultimately will make vocabulary stick is the playful conversational concepts they learned, starting in the crib.

It all begins with a coo.