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This is Scientific American's 60-Second Science. I'm Karen Hopkin. This will just take a minute.

When it comes to pain, it’s the thought that counts. Because pain hurts more when it’s inflicted¹ on purpose. Or so say researchers from Harvard University in the December issue of Psychological Science.

Forty-three people were paired off with a partner for what they were told would be a test of psychological perception. Then they were hooked up to some electrodes, and given a quick zap. Sometimes the shock was “intentional.” So, the partner would call for a shock to be administered, and zzzt it came. But sometimes the shock was unintentional. That is, the partner called for the subject to hear a pleasant tone, but those zap-happy researchers hit the shock button instead.

They then asked the subjects to rate the pain. The results? On a scale of one to seven, with seven being “extremely uncomfortable,” the shocks that were done on purpose rated a respectable 3.6. But the same exact shock when given by accident only rated a 3.

That emotional response to pain makes evolutionary² sense, the researchers say. Because an ouch that’s just an accident is probably one-time thing. Whereas someone who wants to do you harm will probably do it again. In which case it may be a good idea to pull off your electrodes and just go home.

Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.