Since the 1970s when a “marshmallow test” was developed as a means of measuring a child's self control, the ability to resist temptation and delay gratification have been viewed as key predictors of a child's success in life. Now the assumptions behind that finding are being looked at in a different light in a new study published in Psychological Science.

In the marshmallow test children are given a choice: take a single marshmallow immediately, or wait several minutes and earn two marshmallows as a reward.

The marshmallow test came to be seen as an explanation for why disadvantaged children did more poorly in school and were more likely to be violent.

Kids who had the self control necessary to wait for two treats were seen as being not only better at controlling themselves, but more resilient and likely destined for greater academic and economic achievement.

Those who took the marshmallow immediately, rather than waiting, were viewed as lacking self-control and prone to impulse control disorders.

Follow-up studies showed that children raised in poverty were far less likely to delay gratification than their economically better-off counterparts. So the marshmallow test also came to be seen as an explanation for why disadvantaged children did more poorly in school and were more likely to be violent.

If you live in an environment with few resources, however, delaying gratification may not be so advantageous. In fact, it may be a case of “You snooze; you lose.”

“What looks like impulsiveness may actually be an adaptive strategy — kids who are brought up in homes with limited resources have learned it's advantageous to seize the moment,” according to Melissa Sturge-Apple, an associate professor of psychology at the University of Rochester and one of the researchers on the study.

The classic 1970s “marshmallow tests” claimed to assess impulse control in preschoolers. Sturge-Apple and her colleagues measured the physiological quality underlying that ability: the body's ability to slow down heart rate, blood pressure and respiration in order to allow for a thoughtful response. This ability is known as vagal tone.

Information from the heart, lungs, stomach and other organs gets to the brain by way of the vagus nerve, which also helps moderate moods including fear and anxiety. It is part of what makes some people able to cope with stress, suspense, stage fright or delayed gratification better than others.

In children from higher income, high-resource households vagal tone predicts the ability to resist temptation and delay gratification. The higher an economically well-off child's vagal tone, studies found, the longer he or she is able to keep calm, wait and earn additional rewards.

The University of Rochester study found, however, that among children from low-resource households, the opposite is true. When a low-resource child with the same high vagal tone was offered a treat, he or she quickly decided to take it and not wait, despite the promise of more.

“Context means everything,” Sturge Apple explained. “When all is well and prosperous, kids who are highly attuned to what is going on around them can wait, but when things are scarce and unpredictable, then the question becomes ‘why wait?’”

The results don't disprove the earlier research on delayed gratification — it's still a valuable quality — but they do put it in a different context. “ …[W]hen we considered what would be the most optimal behavior in a high-risk environment, then this makes complete sense — it's survival of the quickest,” Sturge-Apple explained. If rewards are scarce, it makes little sense to wait.