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Controlling unwanted thoughts can be difficult for many people. Alpgiray Kelem/Getty Images
  • Most people experience unwanted thoughts from time to time.
  • Some, known as intrusive thoughts, can be linked to psychiatric disorders.
  • A new study has found that most people use reactive thought control to deal with unwanted thoughts once they have occurred.
  • Proactive control—to avoid the thought occurring in the first place—may be more effective, but participants in the study found this very difficult to do.

We all have unwanted thoughts at times. How often have you been trying to concentrate on work, only to find your mind wandering to what you are going to eat that evening, or whether you remembered to turn the stove off?

For most people, unwanted thoughts are just that — distractions that interrupt our focus. But some people experience intrusive thoughts that can be disturbing and distressing.

“Unwanted thoughts are very common, we all experience them to some extent, and the persistence of them can be a symptom of many psychiatric disorders.”

– Dr. Lauren Wadsworth, clinical senior instructor in psychiatry at the School of Medicine and Dentistry of the University of Rochester Medical Center and the founding director of Genesee Valley Psychology and OCD clinic in Rochester, NY.

A new study from the Hebrew University of Jerusalem, published in PLOS Computational Biology, has found that reactive control — acknowledging the thought and then moving the focus back to something else — may help people prevent a thought from immediately coming to mind again. However, full proactive control, which prevents the thought from reaching consciousness in the first place, is much harder to achieve.

Dr. Wadsworth told Medical News Today:

“The investigators used a creative task with the aim of reducing the occurrence of certain thoughts. [They] found significant effects that may be able to inform the development of future skills for psychiatric disorders. However, the thoughts studied in this experiment were not emotionally valenced, limiting the generalizability.”

In the study, 80 paid volunteers were given a free-association task with verbal cues. Participants saw 60 word cues, one at a time, on a computer screen. They had to write an associated word in response to each word. For example, if the presented word was ‘table’, they might write ‘chair’.

Each of the 60 cue words was presented 5 times, in random order.

The researchers divided the participants into 2 equal groups. The control group was allowed to reuse the same associated word when cue words were repeated. People in the test group had to think of a new associated word each time a cue word was repeated. They were told that they would receive no monetary bonus for repeated associations.

They timed how long it took for each participant to respond to each cue. To reduce variation due to typing speed, respondents were told to hit the space bar when they thought of an associated word; they then had to start typing within 1300ms. If they did not start typing in time, the attempt was ended.

To measure the associative strength of their word, the participants were asked to what extent each word reminded them of the cue word on a scale of 0 “not at all” to 10 “very much”.

Dr. Isaac Fradkin, postdoctoral researcher and lead author of the study, explained to MNT:

“In this context — repeated associations (e.g., thinking of ‘chair’ for the second time and so on) are unwanted thoughts; they distract the participant from the goal — to come up with a new association.”

Subjects in the test group who had been incentivized to suppress using the same association with a repeated cue only used the same association 6% of the time compared to 50.5% of the control group’s responses.

As predicted, they took longer to come up with a new associated word compared to when the cue was a repeat. The researchers report that this was consistent with reactive control.

The researchers then excluded the associations which participants had judged to have the strongest association with the cue (as these would have been most difficult to suppress) and concentrated on response times for cues and associations which had been weaker the first time around.

To determine how people were avoiding repeated associations, the researchers used a computational model based on reaction times and how strongly they had recorded the previous associative strength. They found that weaker associative strength increased reaction time compared to the control group, but gave quicker reaction times than when the associative strength was strong, showing the use of proactive thought suppression.

The researchers judged that reactive thought control would delay reaction time, as the person would have to reject the repeat association word and think of another. Proactive control would avoid the unwanted thought (repeat association) altogether, thus speeding up the reaction time.

“Usually, after a person writes ‘chair’ as an association for the first time, it becomes stronger and thus is even more likely to come to mind in the future. We found that participants were able to reduce this self-reinforcing effect of thoughts. This type of control can be described as ‘proactive’ because it makes the unwanted thought not as likely to come to mind in the first place.”

— Dr. Isaac Fradkin

Suppressing unwanted thoughts has been shown to be counterproductive, and can lead to an increase in these thoughts.

Participants in the suppress test group tended to get quicker once they had rejected a repeat association once, thus preventing them from being stuck in a loop with the same repeated association.

This study suggests that distraction, or making the person think about something else, could be more effective in reducing unwanted thoughts.

“[T]he authors imply that the results of their study suggest we can stop thoughts before they happen, however, their task did involve suppression on the part of the participant, which I believe means individuals are still using active behavioral responses to thoughts to reduce future occurrence — as opposed to engaging in a passive process that reduces thought occurrence.”

— Dr. Lauren Wadsworth

Dr. Fradkin advised:

“The challenge is to accept the fact that [when] unwanted thoughts might occasionally (or even frequently) come to mind — to ‘let them be’, without fighting them too much or paying too much attention to them. We need more research to examine how the findings of our study can be used to give concrete advice.”

“Nonetheless, our study has one important and optimistic implication: our brain has the natural ability to keep unwanted thoughts from spiraling. Thus, simply knowing that a particular thought is undesirable or is inconsistent with our current goals might be enough to ensure that even when we do have this thought, it does not make it increase in strength as much as it could have,” he added.