Posted by: wolf | March 7, 2008

Oh, those individualized white bears on my mind
How many times in the past month have you thought about a white bear? Chances are high that you didn’t ever, unless you’ve heard about the polar bear cub “Flocke” (snowflake) that was born in Nuremberg (Germany) and rejected by its mother.

But wait — I am not going to write about Flocke, unbearably (pardon the pun) cute though she may be.

Let me first give some background before I actually comment on the really nice study by Brewin and Smart that earned me the BPR3 icon. For psychogists, the phrase “don’t think of a white bear” is going to ring a bell (I really have to stop that wordplay…). In the ’80s, Daniel Wegner and colleagues published a seminal study on thought suppression where they asked people not to think about a white bear for some time; during that time, participants had to ring a bell whenever they thought of a bear in spite of their attempts at suppressing the idea. The result is a classic:

“It seems that many of us are drawn into what seems a simple task, to stop a thought, when we want to stop thinking of something because it is frightening, disgusting, odd, inconvenient, or just annoying. And when we succumb to that initial impulse to stop, the snowballing begins. We try and fail, and try again, and find that the thought is ever more insistent for all our trying. Many studies reveal that suppression may be the starting point for obsession, rather than the other way around.” (taken from Wegner’s website)

Wegner et al.’s study sparked a lot of interest on thought suppression and intrusion, since intrusive thoughts are among the symptoms of post-traumatic stress disorder (PTSD) and obsessive-compulsive disorder (OCD). PTSD is very common among veterans returning from a war, who often suffer from recurring thoughts of their most terrifying experiences besides other symptoms. PTSD can also be a consequence of rape, accidents, or generally highly stressful, traumatic events. With OCD, people might suffer from experiencing unwanted thoughts with emotionally negative or frightening content, such as imagining to hurt one’s loved ones or thoughts with a sexual content. The unwanted thoughts of people suffering from OCD in many cases don’t appear to be that much frightening or negative — e.g. many people have recurring thoughts about sexual acts — but for the patients, these thoughts feel a lot more negative and distressing than they would for healthy adults. This is why Wegner et al.’s results are so important: The inappropriate attempt at suppressing an unwanted thought might really be involved in developing an obsessive disorder. Intrusive thoughts are treated somewhat differently for OCD and PTSD, and in both cases, symptoms can often at least be reduced using both psychotherapy and medication. However, research still needs to be done on the causes and processes involved in experiencing unwanted, intrusive thoughts and their negative emotional and behavioral consequences.

In an experimental study with healthy subjects, Chris Brewin and Laura Smart from the University College London showed that the ability to suppress thoughts is positively related to their subject’s working memory capacity. Now, “working memory” is one of the red-hot constructs in (neuro-)psychology: try to get a flavor.

However, above being a really popular idea, working memory really is a nice candidate for further exploration of the processes in intrusive thoughts. Working memory might be defined as a system to keep some items of memory in an active state for fast and easy access; paraphrasing Randall Engle, one of the most prominent figures in research on working memory, we might say it is about attention and memory because it enables individuals to keep something in mind (memory) while concentrating on some other task (attention). In Engle’s lab there has been a huge body of research about Working Memory Capacity (WMC): individual differences in the ability to keep things in mind while diverting attention to something else. Brewin and Smart, e.g., have used the operation span task as an operationalization of WMC: people are asked to evaluate the correctness of simple equations and to memorize one to four words at the same time. And then they correlated their subject’s performance in this task (how many target words in the correct order can be recalled after a number of trials) with the number of intrusive thoughts during a five minute period, and also with a measure of negative mood. And really, WMC (measured as operation span task performance) can be used to predict the number of intrusive thoughts: people with a higher WMC were more successful in suppressing an unwanted thought. However, the correlation of negative mood and number of reported intrusions was even higher.

What makes the study interesting from both a practical and methodological perspective is that Brewin and Smart did not again use the ol’ white bear suppression task. Instead, they used a list of frequently encountered intrusive thoughts from clinical studies and asked their participants to select the unwanted thought they had experienced most frequently in the last month, which considerably increases the ecological validity of the experiment. However, it might even be better if participants had been allowed to really freely pick an idea.

The general results and conclusions concerning WMC and intrusive thoughts though are somewhat attenuated given that WMC did not correlate with self-reported number of intrusive thoughts during the last month; again, negative mood was more predictive of that number. Taken together it seems that, even if higher WMC might be helpful in suppressing some thought for a limited time, on the long run it is unrelated to intrusive thoughts.

BREWIN, C., SMART, L. (2005). Working memory capacity and suppression of intrusive thoughts. Journal of Behavior Therapy and Experimental Psychiatry, 36(1), 61-68. DOI: 10.1016/j.jbtep.2004.11.006

P.S. here’s for all you suppressing that thought about the cute little polar bear:

There are even more videos at Flocke’s “official” homepage at the city of Nürnberg:

It’s in German, but “videos” is obvious, and “Bilder” means pictures.


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