In 1995, education researchers Betty Hart and Todd R. Risley published their groundbreaking work on the home language learning experiences of young children in the U.S. “Meaningful Differences in the Everyday Experiences of Young American Children” pointed out an enormous disparity in the number of words addressed to children from high-income versus low-income families by age 3, known as the 30 million word gap.

A powerful predictor of children’s ability to learn and succeed in school is their vocabulary size when entering kindergarten, and this 30 million word gap contributes to differences in early vocabulary development. In addition, more recent research has suggested that parental language use could influence child executive function. Executive function skills like discipline, self-control, and planning are critical for future success and health.

Because children from lower socioeconomic status homes are likely to be at risk for low executive functioning abilities, a new study from New York University’s Neuroscience and Education Lab investigated whether parental language use is a missing link. The researchers found in their model that maternal language input does partially explain the relation between socioeconomic status (SES) and child executive function.

“A powerful predictor of children’s ability to learn and succeed in school is their vocabulary size when entering kindergarten.”

“Conversations provide opportunities for parents to really push their children’s thinking — to have children engage in higher-order cognition and think about things that are not in the immediate present,” said study author Paula Daneri, who presented her results at the Society for Research in Child Development’s (SRCD) Biennial Meeting 2017.

Daneri and her colleagues analyzed data from a longitudinal study of 1,292 families living in North Carolina and Pennsylvania. The final sample included 1,021 children, with almost half being African-American and one-third living below the U.S. poverty line. Measurements took place with the children and parents at ages 15, 24, and 36 months.

Mothers were given a picture book and told to go through the book with their child as they normally would while being video-recorded. During this book sharing task, two variables measured maternal language input: number of different words (NDW) used during the interaction, and mean length of utterance (MLU), which is a proxy measure for complexity. Separate tests recorded child vocabulary and executive function. Six tasks measured three aspects of executive function: working memory, inhibitory control, and attention shifting.

The researchers first confirmed that variance in maternal language input was attributable to income. For all three time points, both NDW and MLU significantly differed between low-SES and high-SES families. Next, they noted that NDW at 24 months and MLU at 36 months could partially explain the relationship between SES and child executive function scores.

“Our hypothesis is that as children age and their language develops, they become attuned to different parts of mothers’ language,” said Daneri.

Around 24 months, children are still building their vocabulary and so more focused on the new words mom uses. But by age three, they’re starting to learn how to put words together into sentences and become attuned to complexity.

A 2012 longitudinal study by Meredith Rowe measured the total number of words parents said to their children during a recorded interaction, how many different word types they used, and their overall complexity of language. During the second year of life, quantity is most important to child vocabulary skill. However, diversity or sophistication of the vocabulary is most important during the third year of life.

“We replicated the same pattern that Rowe had found — that NDW was important around 24 months, but then language complexity became the most important aspect of maternal language input around 36 months,” said Daneri.

In their final model, Daneri and her colleagues saw that the association between SES and child executive function is largely explained by both material language and child language. This conclusion supports their hypothesis that one of the mechanisms through which poverty is associated with lower executive function is a lower quality of mothers’ language.


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