Putting cash in the hands of mothers can help shape the brains of their babies, according to a rigorous randomized study in the United States.
Family income has been linked to child development numerous times in the past in observational studies, but this is the first time researchers have found direct experimental evidence of how poverty drives such changes.
The findings come from an ongoing study known as Baby's First Year, which is attempting to assess how poverty reduction can impact the cognitive and emotional growth of very young children.
"We have known for many years that growing up in poverty puts children at risk for lower school achievement, reduced earnings, and poorer health," explains neuroscientist Kimberly Noble from Columbia University.
"However, until now, we haven't been able to say whether poverty itself causes differences in child development, or whether growing up in poverty is simply associated with other factors that cause those differences."
A thousand low-income mothers in the US were recruited for the study shortly after their babies were born.
These parents, who came from either New York City, New Orleans, Omaha or Minneapolis/St. Paul, were then randomly allocated either $333 a month in unconditional cash payments or $20 a month in unconditional cash payments for the first four years of their baby's life – no strings attached.
Unfortunately, because of the pandemic, only 435 families were able to accommodate in-person tests so that researchers could measure the electrical activity of their baby's brains.
Despite the smaller sample size, the data show that giving low-income mothers financial support can directly change infant brain activity in the first year of life.
Infants whose mothers had received the higher cash payments, for instance, had higher frequency brain activity than those infants whose mothers had received less.
Further research is needed to see whether these changes in brain activity last or whether they translate to improved cognitive development, but there's good reason to suspect they might.
Some small studies have recently shown that high-frequency brain activity is more common in babies born into higher-income families. This type of activity is also associated with higher language, cognitive, and social-emotional scores, although these relationships aren't always consistent.
"All healthy brains are shaped by their environments and experiences, and we are not saying that one group has 'better' brains," says Noble.
"But, because of the randomized design, we know that the $333 per month must have changed children's experiences or environments, and that their brains adapted to those changed circumstances."
Because of the nature of the study, the authors still don't know what environmental factors could have triggered the higher frequency brain waves seen in the trial. They are now investigating whether household expenditures, parental behaviors, family relationships, or family stress had anything to do with the results.
Whatever the reason or reasons, the impact of money on a child's neurodevelopment appears to be a powerful one.
The differences between the two groups was "similar in magnitude to those reported in large-scale education interventions," says economist Greg Duncan from the University of California-Irvine.
The authors hope their results will one day inform better policies for tackling poverty. In particular, the Baby's First Year trial highlights the importance of placing children at the center of these interventions.
"Traditionally, debates over income transfer policies directed at low-income families in the United States have centered on maternal labor supply rather than child well-being," the authors write.
"Our findings underscore the importance of shifting the conversation to focus more attention on whether or how income transfer policies promote children's development."
The study was published in the PNAS.