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Dangers of the Wandering Mind

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Human beings have a remarkable capacity for thought. People can think about things even when they are doing something else quite unrelated. This capacity allows us to be creative and solve problems, but is it always healthy? A recent experiment by Harvard psychologists Matthew Killingsworth and Daniel Gilbert suggests there are emotional costs to a wandering mind. They created a website called at which anyone with an iPhone can sign up and then be randomly called at various times of the day to answer a few questions about their activities and mood at that moment. This method is called “experience sampling” and allows researchers to sample people’s thoughts in real time. This method is a lot more reliable than asking people to complete questionnaires at some later time (e.g., “What were you thinking about last Thursday morning at 9 am?”) An online site also allows for much larger sample sizes, as anyone who finds the site can sign up and become a research subject. Subjects in this experiment were asked when they typically wake up and go to sleep each day. Their waking hours were divided into several time-blocks, and a random call was made in each time-block for as long as each subject was willing to be called. To be included in the study, you had to be available for a minimum of 50 calls. The questions were simple and few:

  1. How are you feeling right now? (answered on a scale of 0 [bad] to 100 [good]
  2. What are you doing right now? (checklist of 22 categories)
  3. Are you thinking about something other than what you are currently doing?
    • No;
    • Yes - something pleasant;
    • Yes - something neutral; or
    • Yes - something unpleasant

Mind wandering was defined as thinking about something other than what you are doing right now (that is, answering Yes to Question #3).

The authors accumulated 2,250 subjects online, all of them over 18 years of age. A little over half (58.8%) are male, and the majority (74%) live in the United States.


1) Mind wandering was reported by 47% of the participants, which is a bigger proportion than what is usually found in laboratory studies of mind wandering.

2) People whose minds were not wandering scored about 70 on the Happiness scale, as did people who whose minds wandered to something pleasant. People whose minds wandered to something unpleasant dropped to about 40 on the Happiness scale. People whose minds wandered to a neutral subject dropped to about 60 on the Happiness scale, suggesting that unless you’ve got a pleasant thought to turn to, thinking about something other than what you’re doing is going to worsen your mood. About 42% of participants’ minds wandered to pleasant thoughts.

3) The researchers also analyzed how the person’s mood or mind wandering at one check-in time influenced mood or mind wandering at the next check-in time. This time- lag analysis found that mind wandering was highly correlated with negative mood at the next check-in, but that mood was not correlated with mind wandering at the next check-in. Thus mind wandering itself may contribute to unhappiness rather than vice versa.

4) Perhaps the most important finding of this study is that what people were thinking at the time of the check-ins was a better predictor of mood than what they were doing. There was some effect of activities on mood, with conversation and exercise rated about 75 on the Happiness Scale and work rated about ten points lower, but by and large mood did not vary much with activity, whereas it did with thoughts, and much of the time people’s thoughts were elsewhere.

This study has implications even for those of us who don’t own iPhones. When we are awake our minds look for something to focus on. Where we direct our attention affects our mood. Focusing on what we are doing at the moment – even if it is mundane, tedious, or repetitive – may be healthier than letting our minds wander, because wandering minds tend to go down a negative path. Once you’re on a negative thought path, it becomes difficult to get off it. Shifting to a more pleasant thought becomes difficult because part of your mind is still trying to shut out the unpleasant thought, which won’t go away (see What’s New article "The Imp of the Perverse.")

By the way, anyone who wants to participate in this study can still go to and sign in. You might also want to study your own thoughts by occasionally stopping in the middle of an activity, mentally stepping back and identifying where your mind actually is. This is called a mindfulness exercise. Are you focused on what you’re doing? If not, where do your thoughts go? Do you naturally turn to positive thoughts, or do you start thinking about something unpleasant?


Killingsworth, M.A. & Gilbert, D.T. (2010) A wandering mind is an unhappy mind. Science, Vol. 330, Page 932.