polar bear intrusion
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Our minds are not entirely under our control. Fyodor Dostoevsky noted as much in 1863, when he penned his famous white bear observation. "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."

Over a century later, social psychologist Daniel Wegner scientifically verified Dostoevsky's claim. Volunteers asked to suppress thoughts of a white bear utterly failed at that task. In a second step, Wegner asked the volunteers to actively think of the bear. He found that original thought suppression group was now able to spend significantly more time picturing the animal than subjects who were asked to think about it from the beginning. Thought suppression, Wegner hypothesized, seems to produce "the very obsession or preoccupation that it is directed against."

While bears on the brain may be a somewhat innocuous preoccupation, Wegner noted that the same backfiring effect often plays out when trying not to ruminate on painful or distressing topics. He explained this phenomenon through the lens of "ironic processes": when trying to suppress a thought, our mind repeatedly checks back in on the thought to make sure we are indeed suppressing it, thus making us think of it more.

In addition, trying hard to control your mind—whether to suppress something or perform a mentally demanding task—requires resources, of which we have a finite amount. "When you try hard to control your mind, your mental resources will inevitably run out and you can no longer maintain the controlling process," says Yunn-Wen Lien, a psychologist at the National Taiwan University. "Both mind wandering and thought suppression failure can be seen as a failure of mental control."

Since Wegner's original discovery, Lien and others have invested effort into finding methods to prevent such failures. Lien's most recent investigation compared the effectiveness of two strategies that seek to suppress thoughts by redirecting attention to either breathing or a mental image. Both were first proposed by Wegner in 2011 as a possible way to "set free the bears," but their effectiveness has never been compared.

In a new study, Lien and her colleague Yu-Jeng Ju divided 82 undergraduates into two groups. One group received training in how to focus on their breath while the other was instructed to direct their attention on the mental image of a blue sports car.

Then, the researchers asked the students to think solely of either the car or their breathing for three minutes, and to push a button each time their mind began to wander. In a second task, the volunteers watched a short video depicting polar bears at play, and then were asked to suppress thoughts about white bears for five minutes by focusing on breathing or the blue car. Again, each time the white bear popped into their minds, they pushed a button. Finally, the researchers also measured the students' working memory—an index of mental capacity—by asking them to remember a series of letters while calculating simple math equations.

As the researchers reported in Consciousness and Cognition, mind wandering and intrusion of unwanted thoughts correlated positively with each other, regardless of which control strategy was used. The more prone a student was to unwanted thoughts, the more likely she was to have high rates of mind wandering.

The researchers also found that focusing on breath rather than on a mental image was a more effective strategy for both reducing unwanted thoughts and cutting back on mind wandering. This might be because focusing on breath requires less energy than focusing on an imaginary image. A third discovery backed this theory up: the effectiveness of the blue car distractor depended on the participant's working memory capacity, while the breathing strategy worked well across the board. "Focused-breathing strategy is effective regardless of users' mental capacities, while focused-distraction strategy only worked for those with high mental capacities," Lien says. This means that the two strategies might operate through different pathways in our brain, she says, although that hypothesis will require further investigation.

This also means that focus on breath might be a particularly useful strategy for those who suffer from depression, anxiety and obsessive-compulsive disorder, since those conditions can erode a person's capacity for mental control. The strategy can be easily applied at home, Lien says, although practice would be required for learning to maintain it for longer than a few minutes, or for combatting especially disturbing subjects.

Breathing is not the only way to suppress unwanted thoughts, however. Other studies suggest distracting activities such as gardening, exercising, arts or handicrafts can produce positive results. Some therapists find that postponing the unwanted thought—allocating 30 minutes to mentally dealing with it later that day or week—can help, too.

Meditation can also increase a person's mental capacity, improving their ability to control thoughts by creating a more stable activity pattern in the default mode network, a set of brain regions active during wakeful rest, and, on the long term, improving self-regulation. "In Taiwan we have a variety of traditional mind-body enhancing practices, in which one's attention is directed to his or her body and the mind is kept 'empty' or 'tranquil,'" Lien says. "Analogously, it allows you to 'reset' your mind, just like you reboot your computer."