It hurts plenty when someone, say, hits you on the head with a badminton racket. But it hurts even more, researchers have found, if you think the hitting was no accident.

Earlier studies have found that the perception of pain can change with how it is experienced. In this case, the perception made the pain worse, the researchers from Harvard University reported in Psychological Science.

The researchers told volunteers that they were going to do a series of tasks, including color matching and“discomfort assessment.”This last task involved their receiving an electric shock.

They were told that a partner in another room would choose which task they would do, and a computer screen alerted them to the choice. In some cases, volunteers were told their partner had chosen the pain test. In others, they were told the computers would select the pain test regardless of their partner’s choice.

When volunteers were under the impression that their partners were inflicting the shocks on purpose, they rated them as more painful, even though they were the same.

ERIC NAGOURNEY