"Try to pose for yourself this task: not to think of a polar bear, and you will see that the cursed thing will come to mind every minute."

That observation comes from "Winter Notes on Summer Impressions," Fyodor Dostoevsky's 1863 account of his travels in Western Europe. But the research that proved it true came more than a century later, from the lab of social psychologist Daniel Wegner, PhD.

Wegner, a psychology professor at Harvard University and the founding father of thought suppression research, first came across the quote more than 25 years ago.

"I was really taken with it," he said in a talk at APA's 2011 Annual Convention. "It seemed so true."

He decided to test the quote's assumption with a simple experiment: He asked participants to verbalize their stream of consciousness for five minutes, while trying not to think of a white bear. If a white bear came to mind, he told them, they should ring a bell. Despite the explicit instructions to avoid it, the participants thought of a white bear more than once per minute, on average.

Next, Wegner asked the participants to do the same exercise, but this time to try to think of a white bear. At that point, the participants thought of a white bear even more often than a different group of participants, who had been told from the beginning to think of white bears. The results suggested that suppressing the thought for the first five minutes caused it to "rebound" even more prominently into the participants' minds later.

The research, published in the Journal of Personality and Social Psychology in 1987 (Vol. 53, No. 1) initiated an entirely new field of study on thought suppression. Over the next decade, Wegner developed his theory of "ironic processes" to explain why it's so hard to tamp down unwanted thoughts. He found evidence that when we try not to think of something, one part of our mind does avoid the forbidden thought, but another part "checks in" every so often to make sure the thought is not coming up—therefore, ironically, bringing it to mind.

After more than a quarter century of this research, Wegner said, he's realized that when he explains his work, listeners usually follow up with one question: "OK, so what do I do about this? Is there any way to avoid unwanted thoughts?"

The topic rings true for many people, perhaps especially because the thoughts that we often want to avoid are not as innocuous as white bears—they might involve painful memories or other difficult distractions.

In his APA presentation, Wegner described several strategies that he and others have come across to help "suppress the white bears." They include:

  • Pick an absorbing distractor and focus on that instead: In one study, Wegner and his colleagues asked participants to think of a red Volkswagen instead of a white bear. They found that giving the participants something else to focus on helped them to avoid the unwanted white bears.

  • Try to postpone the thought: Some research has found that asking people to simply set aside half an hour a day for worrying allows them to avoid worrying during the rest of their day, Wegner said. So next time an unwanted thought comes up, he suggested, just try to tell yourself, "I'm not going to think about that until next Wednesday."

  • Cut back on multitasking: One study found that people under increased mental load show an increase in the availability of thoughts of death—one of the great unwanted thoughts for most people.

  • Exposure: "This is painful," Wegner said, "but it can work." If you allow yourself to think in controlled ways of the thing that you want to avoid, then it will be less likely to pop back into your thoughts at other times.

  • Meditation and mindfulness: There's evidence that these practices, which strengthen mental control, may help people avoid unwanted thoughts, Wegner said.