A landmark 1995 study found that children from higher-income families
hear about 30 million more words during their first three years of life
than children from lower-income families. This “30-million-word gap”
correlates with significant differences in tests of vocabulary, language
development, and reading comprehension.
MIT cognitive scientists have now found that conversation between an
adult and a child appears to change the child’s brain, and that this
back-and-forth conversation is actually more critical to language
development than the word gap. In a study of children between the ages
of 4 and 6, they found that differences in the number of “conversational
turns” accounted for a large portion of the differences in brain
physiology and language skills that they found among the children. This
finding applied to children regardless of parental income or education.
The findings suggest that parents can have considerable influence
over their children’s language and brain development by simply engaging
them in conversation, the researchers say.
“The important thing is not just to talk to your child, but to talk
with your child. It’s not just about dumping language into your child’s
brain, but to actually carry on a conversation with them,” says Rachel
Romeo, a graduate student at Harvard and MIT and the lead author of the
paper, which appears in the Feb. 14 online edition of Psychological Science.
Using functional magnetic resonance imaging (fMRI), the researchers
identified differences in the brain’s response to language that
correlated with the number of conversational turns. In children who
experienced more conversation, Broca’s area, a part of the brain
involved in speech production and language processing, was much more
active while they listened to stories. This brain activation then
predicted children’s scores on language assessments, fully explaining
the income-related differences in children’s language skills.
“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,” says John
Gabrieli, the Grover M. Hermann Professor in Health Sciences and
Technology, a professor of brain and cognitive sciences, a member of
MIT’s McGovern Institute for Brain Research, and the senior author of
Beyond the word gap
Before this study, little was known about how the “word gap” might
translate into differences in the brain. The MIT team set out to find
these differences by comparing the brain scans of children from
different socioeconomic backgrounds.
As part of the study, the researchers used a system called Language
Environment Analysis (LENA) to record every word spoken or heard by each
child. Parents who agreed to have their children participate in the
study were told to have their children wear the recorder for two days,
from the time they woke up until they went to bed.
The recordings were then analyzed by a computer program that yielded
three measurements: the number of words spoken by the child, the number
of words spoken to the child, and the number of times that the child and
an adult took a “conversational turn” — a back-and-forth exchange
initiated by either one.
The researchers found that the number of conversational turns
correlated strongly with the children’s scores on standardized tests of
language skill, including vocabulary, grammar, and verbal reasoning. The
number of conversational turns also correlated with more activity in
Broca’s area, when the children listened to stories while inside an fMRI
These correlations were much stronger than those between the number
of words heard and language scores, and between the number of words
heard and activity in Broca’s area.
This result aligns with other recent findings, Romeo says, “but
there’s still a popular notion that there’s this 30-million-word gap,
and we need to dump words into these kids — just talk to them all day
long, or maybe sit them in front of a TV that will talk to them.
However, the brain data show that it really seems to be this interactive
dialogue that is more strongly related to neural processing.”
The researchers believe interactive conversation gives children more
of an opportunity to practice their communication skills, including the
ability to understand what another person is trying to say and to
respond in an appropriate way.
While children from higher-income families were exposed to more
language on average, children from lower-income families who experienced
a high number of conversational turns had language skills and Broca’s
area brain activity similar to those of children who came from
“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,”
The researchers hope their findings will encourage parents to engage
their young children in more conversation. Although this study was done
in children age 4 to 6, this type of turn-taking can also be done with
much younger children, by making sounds back and forth or making faces,
the researchers say.
“One of the things we’re excited about is that it feels like a
relatively actionable thing because it’s specific. That doesn’t mean
it’s easy for less educated families, under greater economic stress, to
have more conversation with their child. But at the same time, it’s a
targeted, specific action, and there may be ways to promote or encourage
that,” Gabrieli says.
Roberta Golinkoff, a professor of education at the University of
Delaware School of Education, says the new study presents an important
finding that adds to the evidence that it’s not just the number of words
children hear that is significant for their language development.
“You can talk to a child until you’re blue in the face, but if you’re
not engaging with the child and having a conversational duet about what
the child is interested in, you’re not going to give the child the
language processing skills that they need,” says Golinkoff, who was not
involved in the study. “If you can get the child to participate, not
just listen, that will allow the child to have a better language
The MIT researchers now hope to study the effects of possible
interventions that incorporate more conversation into young children’s
lives. These could include technological assistance, such as computer
programs that can converse or electronic reminders to parents to engage
their children in conversation.