Kindergarten teachers in the poorest neighborhoods of Montreal rated 920 6-year-old boys using scales measuring inattention, hyperactivity, defiant behavior, aggression and prosociality (the tendency to help someone being hurt, stop quarrels or invite a bystander into a game). Researchers then gathered information on earnings from tax returns at ages 35 to 36. The study is in JAMA Pediatrics.

After controlling for I.Q. and family adversity, the scientists found that boys in the highest one-quarter for inattention later earned an average of about $17,000 less a year than those in the lowest one-fourth. Those in the highest one-quarter for scores in prosociality earned an average of about $12,000 more annually than those in the lowest.

Although there was a tendency for higher scores in hyperactivity, defiant behavior and aggression to lead to lower income, the effect was not statistically significant. The authors caution that the results may not apply to other socioeconomic populations.