Time and again, poor children have performed significantly worse than their more fortunate counterparts. A 2011 study that looked at low-income children in Chicago noted how poor children struggled to delay gratification. A 2002 study, which examined the physical and psychological stresses that accompany poverty, did too. And so have many others.
The realization has sparked concerns that poverty begets a certain level of impulsiveness, and that that tendency to act in the moment, on a whim, without fully considering the consequences, makes it all the more difficult for poor children to succeed. But there's an important thing this discussion seems to miss. Poor kids may simply not want to delay gratification. Put another way, their decisions may not reflect the sort of impulsive nature we tend to attribute them to.
"When resources are low and scarce, the rational decision is to take the immediate benefit and to discount the future gain," said Melissa Sturge-Apple, a professor of psychology at the University of Rochester who studies child development. "When children are faced with economic uncertainty, impoverished conditions, not knowing when the next meal is, etc. — they may be better off if they take what is in front of them." (Source)
The experimenters used vagal tone to look at performance under stress and found low-SES inverted decision making for those with high vagal tone -- in other words, maybe they weren't impulsive -- maybe they were acting just like they intended.