Perry Edward Smith, the killer who would be hanged for the murder of a four-person Kansas family, famously told Truman Capote: “I despise people who can’t control themselves.” Capote called the book In Cold Blood, and it turns out that all might have been more literally true than either Capote or Smith anticipated.

A study published Wednesday in JAMA Psychiatry, analyzing 710,000 men, found that a slow heartbeat early in life was a sign of a future capacity for violence. The Philadelphia Inquirer reports that as adults, the men were 49 percent more likely to be convicted of violent crimes and 25 percent more likely to be convicted of nonviolent crimes. That matches up with previous data that suggested a low resting heart rate was connected to antisocial behavior.

The steady beat could be a sign that these men are not especially anxious and, therefore, are more likely to take risks than their more nervous counterparts. Another theory is that they become thrill-seekers to boost their “suboptimal” arousal levels. On the bright side, a low resting heart rate could be used for good in professions that require steady nerves, like bomb disposal experts or firefighters, so don’t go turning your kid over to the police just because he’s preternaturally calm. Just try to mold that kid right. Please.

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