The gap in language skills between children from low-income families and those from affluent homes becomes evident when children are as young as 18 months old, according to new research in Developmental Science.
Researchers Anne Fernald, Virginia Marchman and Adriana Weisleder from Stanford University studied 48 children whose families were either low-income, from communities with a median annual income of $23,900, or from more affluent families in communities with an average income of $69,000.
Other socioeconomic factors also separated the groups, including the mothers’ level of education: Nearly 90 percent of mothers in the higher-income group had at least a four-year college degree compared to 30 percent of the lower-income mothers. All the children came from English-speaking families, but were of varied races: 66 percent were white, 13 percent Asian, 10 percent Alaskan native or Native American, 6 percent native Hawaiian or Pacific Islander and 4 percent African-American.
By measuring the vocabularies of the children when they were both 18 months and 24 months old, researchers found that children’s ability to express themselves was highly correlated with family income. At 18 months, the children from the lower-income families had an average vocabulary of 110 words, approximately 70 fewer words than the vocabulary of the affluent children.
Both groups had bigger vocabularies six months later at age 24 months. But the higher-income children gained about 80 more words during this period than the lower-income group, having about 450 words at age 2 compared to 300 for the lower-income group.
Researchers also examined each child’s skill at accurately and quickly processing words spoken to them and found that the affluent children responded more quickly and with substantially greater accuracy. When the higher-income children were 18 months old, their average accuracy rate was identical to that of the poorer children at 24 months, putting them six months ahead.
These findings reinforce earlier research showing that children of professional parents hear 30 million more words by age 3 than children from low-income households. The researchers for this study explain that levels of social, psychological, medical and nutritional support for families vary along socioeconomic lines as do levels of stress and instability. All these factors affect the quality of parent-child interactions and lead to differences in language skills.