Many parents wonder what they can do to help set their toddlers up for success in preschool, kindergarten, and beyond. A new study published in the journal <a href="https://onlinelibrary.wiley.com/doi/10.1111/cdev.12398/abstract){: target="_blank" rel="nofollow" } by [Penn State](https://www.noodle.com/colleges/coq/pennsylvania-state-university-main-campus" target="_blank">Child Development Associate Professor Paul L. Morgan and colleagues isolates one factor that is uniquely predictive of both academic and behavioral achievement: a child’s oral vocabulary at age two.

The term “oral vocabulary" refers to the words children either use when speaking or recognize when listening. Studies suggest that 90 percent of English-speaking, 24-month-olds have an expressive vocabulary of at least 40–50 words, and many of these toddlers know substantially more — according to some studies, nearly double. These developmental trends span across languages, too. For example, 90 percent of Spanish-speaking, 24–26-month-olds also have average expressive vocabularies of at least 40 words. With each passing day, young children’s vocabularies seem to grow exponentially, and by the time a child reaches six years old, she will know and be able to use more than 10,000 words on average.

Importance of Oral Vocabulary

Interest in children’s vocabulary development is not new; linguists and developmental psychologists have long studied the emergence of children’s phonological and lexical development — that is, their understanding of sound and meaning — and the roles that parents play in supporting children’s growing capabilities. Similarly, researchers have long theorized relationships between children’s early vocabularies and their academic and social achievements. Yet it is only recently that sufficiently large data samples and statistical capabilities have enabled experts to evaluate with rigor the unique contribution of early oral vocabulary to children’s achievement.

The link between young children’s vocabulary and their eventual abilities to read and write are fairly evident to most parents — having a strong vocabulary enables children to better identify and decode words phonetically, making listening, reading, and sounding them out easier. But how does knowing many words at age two relate to children’s performance in later academic or social development? The recent study by Morgan and his fellow researchers sought to identify exactly these predictive associations.

Indeed, one of the reasons this investigation is so impressive is the extent to which the authors attempted to separate out all of the other factors that may have an impact on either children’s vocabularies or their academic and social achievement. Aiming to isolate only the predictive associations of oral vocabulary at this age, the authors accounted for three groups of factors that may also play a role in early language development:

1. Information on sociodemographic variables

• family socioeconomic status, race, or ethnicity
• mother’s age and marital status
• types of stimulation children received at home
• parental health problems, including depression
• amount of television children watched
• amount of time children spent in child care

2. Characteristics related to pregnancy and children’s birth

• low birthweight
• being one of a multiple birth (twins, triplets, and so on)
• medical risks and complications during pregnancy which are often associated with later developmental delays

3. Children’s early cognitive and behavioral functioning

• attention, persistence, and so on
• aggressive and anxious behaviors

After controlling for these other factors that also influence children’s development, the authors found that oral vocabularies were consistently associated with reading and math achievement at age five, when these young students entered kindergarten. Children who knew more words at 24 months scored higher on reading and math tests in kindergarten than those who had had smaller vocabularies as toddlers.

Interestingly, having a larger vocabulary at age two was a stronger predictor of kindergarten math scores than reading scores. One possible explanation for this surprising finding is that learning mathematical concepts requires children to be able to think more abstractly than when they are reading words and sounding out letters. Knowing more words as a 2-year-old may enable children to better understand math lessons because they’ve built a larger vocabulary related to early math concepts (such as patterns and quantities, for instance).

Morgan and his colleagues, moreover, found that children with larger early vocabularies were less likely to be described by their teachers as showing problematic behaviors and more likely to regulate their attention and persist at difficult tasks, all important components of learning. Having a larger vocabulary enables children to express their feelings, wants, and needs, contributing to less frustration and negative behaviors like temper tantrums. Having a larger vocabulary may also make children more interesting and fun for peers, teachers, and parents to interact with – thus enabling them to practice these social-emotional skills more frequently.

Factors That Affect a 2-Year-Old’s Vocabulary

Perhaps not surprisingly, the greatest predictor of a child’s early vocabulary is her family’s socioeconomic status; children from wealthier households in the Morgan study had a greater vocabulary than those in the lowest income group, a finding that has been identified consistently by researchers for decades. An earlier study from 1995 by researchers Betty Hart and Todd R. Risley found that by age four, children in families receiving welfare support had experienced 30 million fewer words than the average child with parents holding white-collar jobs.

# The Role of Parents

Both the Morgan study and previous research have emphasized the important role parents can play in enriching their children’s language exposure. Parents who were warm and supportive, provided toys and books for their child, and took the child to public educational places, raised children with higher oral vocabularies. The Hart and Risley study also showed how parent sensitivity contributed to children’s vocabularies. Adults in higher-income homes not only used more words around their children, but directed six times as many encouraging words toward them compared to parents in lower-income homes. This support may enable a child to persist through challenging or cognitively frustrating tasks and give her confidence to explain herself and practice using her emerging language skills. A lack of encouragement — or even outright discouragement — may serve to diminish children’s expression, in turn stunting their vocabulary growth.

# The Impact of Household Environment

Other factors that put a child at risk for a rocky kindergarten entry included high television usage — that is, more than 17 hours per week — and having a family member with a mental or physical illness. Although parents may believe that watching television exposes children to sufficient language, cognitive psychology research has shown that children (and adults) do not learn as well from television as they do from direct interaction. When this activity displaces opportunities for children and adults to interact or for children to observe other family members in conversation, these young learners miss out on the opportunity to hear and practice using new words.

As with poverty, Morgan and colleagues hypothesize that the stress a family experiences when struggling with mental or chronic illness has a negative impact on a child’s vocabulary development. A parent whose attention is necessarily diverted to another family member may not speak to a child with the frequency needed for a toddler to develop an extensive vocabulary. Interestingly, twins also showed lower oral vocabularies at age two, and the authors hypothesized that in these households, parents’ attention is divided between two or more children, reducing each child’s direct exposure below the overall number a single child would experience.

Supporting Your Toddler’s Vocabulary

Findings from these studies indicate that parental investment in expanding a toddler’s vocabulary is worthwhile because of how malleable young children are and how great the benefit is for their future achievement. Still, this doesn’t mean you need to whip out the flashcards. Children will learn new words through exposure — by some estimates, over 90 percent of a child’s vocabulary is developed just by engaging with her parents — so the single best thing an adult can do is talk. A lot. Talk with your child, even if she hasn't yet reached language milestones that would enable her to respond.

# Narrate Activtities

Narrate what you do when you’re together: “I’m walking over to the refrigerator, and I’m going to get out some watermelon for your snack. Do you remember when we had watermelon at the picnic last week?"

# Label Objects

Use language to enrich your child’s experiences of new places. For example, when you go to the grocery store, label the things you put in your cart, point out new fruits and vegetables in the produce section, and describe them: “Look at the eggplant! It’s purple! Can we find another purple fruit or vegetable? Oh look, a plum! Those are purple too!"

# Use Synonyms

Try to challenge yourself to use a variety of words — use synonyms back to back so your child can map the new word onto a word that is already familiar: “You went down the slide so fast! You went really quickly!"

# Be Patient

Be patient with your new talker and gently encourage and repeat what she is saying, making subtle grammatical corrections. By repeating children’s utterances, parents provide feedback that helps young speakers know they are heard and understood. And try to refrain from telling a child to hush or “not now," which may unintentionally limit her opportunities to practice using new words and build confidence expressing herself.

# Praise Trying

It’s also helpful to support your child’s attempts to use new language through praise and encouragement. Researchers Hart and Risley demonstrated that parents who invited their children’s expressions of speech positively saw them develop larger vocabularies, an outcome that the authors attribute to the confidence the children gained to speak frequently and express their feelings and desires.

Research has firmly established the importance of vocabulary for children’s long-term academic success, as well as the obvious role it plays in their ability to communicate effectively, making social interactions more enjoyable for children, parents, peers, and teachers. The significance of these insights is that they encourage parents to talk often and at length with their young children — which, in turn, helps to foster family bonds that support more learning along the way.

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