> and that many preferred to administer electric shocks to themselves instead of being left alone with their thoughts.

I see this study cited often, and I always reject this interpretation. I'm perfectly content sitting for long periods, with or without my thoughts, but if you give me an electric toy I've never seen before, of course I'll play with it! Can I make muscles twitch? Move my arm? Are some parts more sensitive/conductive? What happens at the limits?

For me, the pain would be the cost of playing with a new toy that gives me novel sensations. I would do it even if I had other, less painful activities available. It's not necessarily a way to avoid boredom or whatever else the common interpretation claims.