Neuroscientists who study language are keenly aware that the playing field is not level when it comes to acquisition. In the first few years of life, the brain is ripe for learning, picking up hundreds of words from their caregivers and their environment.
In 1995 a ground-breaking study showed that children who grow up in families with higher incomes hear about 30 million more words during the first three years of life than children from lower income families. Dubbed the "30 Million Word Gap" it is part of ongoing research since there were associations between income and differences in achievement on tests that measure vocabulary and reading comprehension.
Researchers from MIT, who study language and cognition have published research that shows back and forth conversation between adults and children causes changes in the child's brain and this conversational exchange is more important in language development that the word gap. The team worked with children aged 4 to 6 years, and when they looked at differences in how many "conversational turns" children took, they found that those differences were due, in large part, to differences in brain anatomy and language development. The differences and associations were irrespective of socioeconomic status or education. The results of this study are a strong suggestion that any negative impact that education and income have on language can be offset by engaging children in conversation on a regular basis.
Using functional MRI (fMRI) imaging, the teams looked at brain differences. The study volunteers, a brave group of very young patients, listened to stories while in an MRI scanner. The images showed that in children who had a lot of experience in conversing with adults, Broca's area, which is known to be the hub of language processing and speech, was more active. Children who didn't have that much experience talking with adults, had less activity in this area, suggesting that actual brain changes can be the result of having an age-appropriate conversation with adults. Speaking with children produces better results than just piling on the vocabulary.
John Gabrieli is a professor of brain and cognitive sciences and a member of MIT's McGovern Institute for Brain Research. He is also the senior author of the work and explained the results, stating, "The really novel thing about our paper is that it provides the first evidence that family conversation at home is associated with brain development in children. It's almost magical how parental conversation appears to influence the biological growth of the brain."
While researchers know that the word gap exists, there was little to no information on the underlying mechanism of what the gap means regarding brain differences and cognitive skills. By recruiting subjects at different income levels, and collecting brain image studies, the researchers hoped to learn exactly what the gap means for children as they grow up. Getting the MRI scans was easy enough, however obtaining accurate data on the language used by the children and their families required them to ask children to wear recorders for two days, from the moment they woke up until they went to sleep. Every word spoken by or to the children was recorded on the devices.
A computer program analyzed the recordings and tallied up the number of words spoken by the child, the number of words spoken by an adult to the child and how many conversational turns the children and adults took. There was a strong correlation between higher scores on tests including grammar, vocabulary and verbal reasoning, and the number of conversations the children engaged in. There was also a close relationship between these conversations and how active Broca's area was while the children listened to stories in the MRI scanner. The number of words heard and spoken by the children was not as closely associated with brain activity and performance on tests. The conversations were the key, not income, education or number of words.
While it's a fact that children in higher income homes are exposed to more language, the data from the study showed that children from lower income homes could have test scores and Broca activity similar to their wealthier playmates, if they had a lot of conversation happening on a daily basis. Dr. Gabrieli summarized the work, writing, "In our analysis, the conversational turn-taking seems like the thing that makes a difference, regardless of socioeconomic status. Such turn-taking occurs more often in families from a higher socioeconomic status, but children coming from families with lesser income or parental education showed the same benefits from conversational turn-taking."