NEW YORK ( MainStreet) — Children in families that pay more than 30% of their income toward rent -- an increasingly common phenomenon in the U.S. -- may more commonly experience cognitive difficulties.

According to a new study out of Johns Hopkins, that households that spend approximately a third of their income on rent reap the most benefits in terms of their children's intellectual capacity. In fact, though the 30% figure has often been touted as the ideal amount one should spend on rent, little research has been devoted to justifying that estimate until now.

The study, conducted by Johns Hopkins policy professor Sandra J. Newman and researcher C. Scott Holupka, analyzed the impacts of affordable housing on physical health, emotional well-being, and cognitive development of children living in low-income households.

Newman discovered that though a family's rent-to-income ratio did not affect their children's physical or social health, it had a somewhat significant impact on cognitive aptitude. This is because families who are rent burdened do not have the extra money to spend on enriching resources and activities for their kids, such as books, computers, games or outings to places like museums and aquariums. In particular, families who spent about a third of their income on housing were found to have spent an average of $98 more on their children every month than other families in the sample.

"Families spending about 30% of their income on housing had children with the best cognitive outcomes," said Newman, who is also director of the university's Center on Housing, Neighborhoods and Communities.

That's especially damning for the poor , as a report released by the Joint Center for Housing Studies of Harvard University at the end of last year found that half of all U.S. households now pay more than 30% of their incomes toward rent, with a quarter of all households spending more than half of their incomes on rent. And while half of all households pay more than 30% of their income on rent, that figure is considerably higher for those in the lowest income demographic -- 88%, according to the 2009 American Community Survey.

To reach the conclusions about pediatric cognition in the Johns Hopkins study, Newman and her colleague relied on data compiled by The Panel Study of Income Dynamics, which was piloted in the 1960s and has analyzed 5,000 families. As part of the Panel's Child Development Supplements, the children of these families were tested at various stages of development for cognitive abilities using the "Woodcock Johnson Test." Newman then compared this data with 2004-2009 Consumer Expenditure Surveys, focusing on families at or below 200% of poverty line and with a fairly diverse racial distribution (36% white, 42% black, and 18% Hispanic).