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What makes us happy? It’s one of the most complicated puzzles of human existence — and one that, so far, 87 speakers have explored in TEDTalks.

In today’s talk, Matt Killingsworth (who studied under Dan Gilbert at Harvard) shares a novel approach to the study of happiness — an app, Track Your Happiness, which allows people to chart their feelings on a moment-by-moment basis. As they go about their day, app users get random pings, asking them to share their current activity and note their mood. When Killingsworth gave this talk at TEDxCambridge in 2011, the app had collected data from more than 15,000 people in 80 countries, representing a wide range of ages, education levels and occupations. In this talk, Killingsworth reveals a very surprising finding: that mind-wandering appears to factor heavily into this happiness equation.

“As human beings, we have this unique ability to have our minds stray,” says Killingsworth on the TEDx stage. “This ability to focus our attention on something other than the present is amazing — it allows us to learn and plan and reason.”

While most people think of mind-wandering as a lifting escape from daily drudgery, the Track Your Happiness data shows that this may not the case. In fact, mind-wandering appears to be correlated with unhappiness. When people were mind-wandering, they reported feeling happy only 56% of the time. Meanwhile, when they were focused on the present moment, they reported feeling happy 66% of the time. This effect was true regardless of the activity the person was doing — be it waiting in a traffic jam or eating a delicious dinner. (Read Killingsworth’s study, published in the journal Science in 2010, to see a breakdown of mind-wandering rates by activity.)

According to Killingsworth’s data, people mind-wander most when in the shower and least when they are having sex. But, still, mind-wandering is a constant. Overall, people mind-wander 47% of the time. Perhaps not such a good thing if it relates to unhappiness,

To hear more about mind-wandering — and about the importance of studying happiness in general — watch Killingsworth’s talk. And after the jump, read several more fascinating studies on the psychology of mind-wandering — some of which will make you feel better about your daydreaming.

A relationship to working memory
Mind-wandering might make us feel less content, but it could also have a functional purpose. A recent study published in the journal Psychological Science suggests that mind-wandering might be a sign of a high capacity working memory — in other words, the ability to think about multiple things at once. Researchers asked study participants to press a button and, as they went, checked in to see if their minds were wandering. After the task was complete, researchers gave participants a measure of their working memory. Interestingly, those who were found to be frequent mind-wanderers during the first task showed a greater capacity of working memory. Researcher Jonathan Smallwood of the Max Planck Institute for Human Cognitive and Brain Science explains, “Our results suggest that the sorts of planning that people do quite often in daily life — when they’re on the bus, when they’re cycling to work, when they’re in the shower — are probably supported by working memory. Their brains are trying to allocate resources to the most pressing problems.”

A key to memory formation
Mind-wandering might also play a vital function in helping us form memories. New York University neuroscientist Arielle Tambini looked at memory consolidation in this study published in the journal Neuron in 2010. Participants in the study were asked to look at pairs of images and, in between, were instructed to take a break to think about anything they wanted. Using fMRI, the researchers looked at the activity in the hippocampus cortical regions while they did both. The study showed that these two areas of the brain appear to work together — and that the greater the levels of brain activity in both areas, the stronger the subjects’ recall of the image pairing was. Explains Lila Davichi, who oversaw the study, “Your brain is working for you when you’re resting, so rest is important for memory and cognitive function. This is something we don’t appreciate much, especially when today’s information technologies keep us working round-the-clock … Taking a coffee break after class can actually help you retain that information you just learned.”

A creative boost
As the cliché goes, the best ideas usually come when you are least expecting them. A recent study published in the journal Psychological Science gives a clue as to why. A research team led by Benjamin Baird and Jonathan Schooler of the University of California at Santa Barbara asked participants to take “unusual uses” tests — brainstorming alternate ways to use an everyday object like a toothpick for two minutes. Study participants did two of these sessions, and then were given a 12-minute break, during which they were asked to rest, perform a demanding memory exercise or do a reaction time activity designed to maximize their mind-wandering. After the break, they did four more unusual uses tests — two of them repeats. While all of the groups performed comparably on the two new unusual uses lists, the group that had performed the mind-wandering tasks performed 41% better then the other groups on the unusual uses lists they were repeating. “The implication is that mind-wandering was only helpful for problems that were already being mentally chewed on. It didn’t seem to lead to a general increase in creative problem-solving ability,” says Baird.