These differences can also be measured in the brain, said Columbia University neurologist and pediatrician Kimberly Noble.
Olexander Zobin, AFP/File
The best way for babies to learn is to be spoken to like adults, researchers say
The human brain experiences incredible growth in its early years.
By the age of three, it has formed 1,000 trillion neural connections -- the links between cells that help the brain do everything from picking up a stick to remembering song lyrics.
"A child's experiences really come into play to determine whether those connections strengthen or are dropped or pruned," Noble told reporters at the American Association for the Advancement of Science's annual meeting.
Noble and her colleagues compared the brains of children with low socioeconomic status to those whose parents are highly educated and paid well.
While they found differences in the core cognitive systems that support social skills and memory, the largest disparities were in the brain structures for language development.
"With increasing age, children from higher socioeconomic backgrounds devoted more neural real estate to those regions," she said.
- 'Rich, varied language' early -
Stanford University psychologist Anne Fernald has found that the language gap can be measured as early as 18 months. By a child's second birthday that gap is already six months wide.
Jacques Demarthon, AFP/File
By the time they reach the age of five, the children of disadvantaged backgrounds typically score two years behind their privileged peers
Fernald and her colleagues made recordings of what a group of low-income, Spanish-speaking children heard all day.
They found that infants didn't gain much from simply overhearing their parents and caregivers talk -- the real learning came from being spoken to directly.
It is crucial to develop "culturally sensitive interventions" to teach low-income parents to talk to their children, Fernald told reporters.
"There's a wide range of views about whether it's even appropriate to talk to a child -- in some cultures it is not," Fernald said.
A pilot project she is running in San Jose to teach Latina mothers to engage verbally with their children has shown promising results.
"By 24 months, the children of more engaged moms are developing bigger vocabularies and processing spoken language more efficiently," Fernald said.
While parents might want to help their children prepare for school by speaking to them in English, Hoff said they are usually better off sticking to their native tongue.
A study she was set to present on Friday showed that when parents don't have a firm grasp of a second language, they aren't able to teach it to their children.
Instead, they end up limiting their children's overall language development by failing to expose them to more complex speech.
"We want to do whatever it takes to give children access to rich, varied language input at an early age," Hoff said.
Parents wanting to enrich their children with a bilingual education also have to weigh the cost.
"Learning two languages is a great thing. What we have to recognize is that learning two languages does not happen for free," Hoff said. "You don't learn two languages as quickly as you learn one."