Adapted from Hart & Risley, 1995

What are some factors that determine the rate of vocabulary growth in young children? Some of the differences in children’s vocabulary size come from their personalities. For example, some children start talking without much understanding of what they are saying. Other children may be more cautious. Some children are also more social than others, and thus may be more driven to talk.

Besides these “child specific” factors, a child’s language experience plays an important role. Both the amount and the type of language that children hear relates to their vocabulary size. The number of words children hear is related to the number of words they produce.

Now look at the graph. The child’s age is on the bottom of the graph, and vocabulary size is on the left side. This graph shows that children produce more words as they get older. But not all children learn words at the same rate. What other factors might influence children’s word learning?

A family’s socioeconomic status (SES) is one factor that is linked to language development. SES is a measure of a family’s economic resources. It includes factors like parents’ education, occupation, and salary. You can think of SES as a measure of opportunities. Children from low-SES families often have more limited access to resources. They also have fewer opportunities such as access to books and high-quality childcare. On average, children from low-SES families hear fewer words than children from higher-SES families. For example, an average child from a low-SES family hears about 600 words per hour. An average child from a high-SES family hears over 2000 words per hour. Over time, this discrepancy produces a wide gap in the number of words a child has heard. By 3 years of age, children from high-SES families have heard 30 million more words than children from low-SES families.