A new study suggests that stressful childhoods are responsible for the achievement gap:

Given a sequence of items to remember‚ teenagers who grew up in poverty remembered an average of 8.5 items. Those who were well-off during childhood remembered an average of 9.44 items. So-called working memory is considered a reliable indicator of reading, language and problem-solving ability — capacities critical for adult success.

When Evans and Schamberg controlled for birth weight, maternal education, parental marital status and parenting styles, the effect remained. When they mathematically adjusted for youthful stress levels, the difference disappeared.

In lab animals, stress hormones and high blood pressure are associated with reduced cell connectivity and smaller volumes in the prefrontal cortex and hippocampus. It’s in these brain regions that working memory is centered. Evans and Schamberg didn’t scan their human subjects’ brains, but the test results suggest that the same basic mechanisms operate in kids.

Jonah Lehrer adds his own thoughts.

(Photo: an orphaned boy in Gaza by Mahmud Hams//AFP/Getty.)