Many people would rather inflict pain on themselves than spend 15 minutes in a room with nothing to do but think, according to a US study.
Researchers at the University of Virginia and Harvard University conducted 11 different experiments to see how people reacted to being asked to spend some time alone.
Just over 200 people participated in the experiments, in which researchers asked them to sit alone in an unadorned room, and report back on what it was like to entertain themselves with their thoughts for between six and 15 minutes.
About half found the experience was unpleasant.
"Most people do not enjoy 'just thinking' and clearly prefer having something else to do," said the study in the journal Science.
Researchers then turned their attention to what people were doing to avoid being alone with their thoughts.
In one experiment, students were asked to do the "thinking time" exercise at home.
Afterward, 32 per cent reported they had cheated by getting out of their chair, listening to music or consulting their mobile phone.
An initial pilot study found, surprisingly, that students preferred to hear the sound of a scraping knife to hearing no noise at all.
"We thought, surely, people wouldn't shock themselves," co-author Erin Westgate, a PhD student at the University of Virginia, said.
They offered participants a chance to rate various stimuli, from seeing attractive photographs to the feeling of being given an electric shock about as strong as one that might come from dragging one's feet on a carpet. After the participants felt the shock, some even said they would prefer to pay $5 than feel it again.
Then each subject went into a room for 15 minutes of thinking time alone. They were told they had the opportunity to shock themselves, if desired.
Two-thirds of the male subjects - 12 out of 18 - gave themselves at least one shock while they were alone. Most of the men shocked themselves between one and four times, although one "outlier" shocked himself 190 times.
A quarter of the women, six out of 24, decided to shock themselves, each between one and nine times.
All of those who shocked themselves had previously said they would have paid to avoid it.
Westgate said she is still astounded by those findings. "I think we just vastly underestimated both how hard it is to purposely engage in pleasant thought and how strongly we desire external stimulation from the world around us, even when that stimulation is actively unpleasant."