In 2014, one in 16 Americans visited the ER for home injuries that resulted from, among other things, fumbling knives (the cause of at least 249,000 injuries), ladders (at least 105,000), and cookware (at least 22,000). One of the main causes of these accidents? A wandering mind, says Steve Casner, the author of Careful: A User’s Guide to Our Injury-Prone Minds. By one estimate, he notes, people daydream through nearly half their waking hours.
Psychologists have recently focused more intently on the tendency to think about something other than the task at hand. For one experiment, two Harvard researchers developed an iPhone app to analyze the relationship between daydreaming and happiness. The average person’s mind, the researchers found, wandered most frequently (about 65 percent of the time) during personal-grooming activities, and least often (10 percent of the time) during sex. Respondents’ minds tended to wander more when they felt upset rather than happy, and were more likely to wander toward pleasant topics than unpleasant ones. 
Drinking alcohol and daydreaming also seem to go hand in hand. In one study, participants who imbibed a moderate amount daydreamed roughly twice as much as those given a placebo drink.  And the younger we are, the more likely we may be to let our mind wander. People ages 18 to 25 report significantly more task-unrelated thoughts than do those ages 60 to 85. 
How do daydreams affect daydreamers? Just as a wandering mind makes us accident-prone at home, it leaves us vulnerable behind the wheel. In an unusual study, French researchers visited an ER to interview 955 patients involved in traffic accidents. The majority of them reported having daydreamed just before the crash; more than 10 percent considered the daydream’s content “highly disrupting/distracting.”  And many studies have shown that mind-wandering interferes with cognitive functions such as reading comprehension and memory retention. 
Yet other research suggests that daydreaming has benefits. For one, much mind-wandering is future-oriented, and researchers have found that it gives us a chance to think about our goals.  It also seems to bolster creativity. In one experiment, 145 undergraduates completed four “unusual uses” tasks, each requiring them to list as many uses as possible for an everyday object. After the first pair of tasks was completed, one group of subjects was assigned an undemanding activity intended to elicit mind-wandering. When the subjects proceeded to the second pair of tasks, the daydreamers performed 40 percent better than the non-dreamers. 
So what are people daydreaming about at any given moment? Most of us prefer not to say. One University of Minnesota survey found that 79 percent of adults would rather admit to a humiliating experience than divulge their daydreams.  Even more embarrassing than falling off a ladder, in other words, might be the thoughts that led you to do so.
 Killingsworth and Gilbert, “A Wandering Mind Is an Unhappy Mind” (Science, Nov. 2010)
 Sayette et al., “Lost in the Sauce” (Psychological Science, June 2009)
 Frank et al., “Validating Older Adults’ Reports of Less Mind-Wandering” (Psychology and Aging, June 2015)
 Galéra et al., “Mind Wandering and Driving” (British Medical Journal, Dec. 2012)
 Mooneyham and Schooler, “The Costs and Benefits of Mind-Wandering” (Canadian Journal of Experimental Psychology, March 2013)
 Baird et al., “Back to the Future” (Consciousness and Cognition, Dec. 2011)
 Baird et al., “Inspired by Distraction” (Psychological Science, Oct. 2012)
 Klinger et al., “Disclosing Daydreams Versus Real Experiences” (Imagination, Cognition and Personality, Oct. 2004)