Despite those who romanticize depression as the wellspring of artistic genius, studies find that people are most creative when they are in a good mood, and now researchers may have explained why: For better or worse, happy people have a harder time focusing.

University of Toronto psychologists induced a happy, sad or neutral state in each of 24 participants by playing them specially chosen musical selections. To instill happiness, for example, they played a jazzy version of Bach's Brandenburg Concerto No. 3. After each musical interlude, the researchers gave subjects two tests to assess their creativity and concentration.

In one test, participants in a happy mood were better able to come up with a word that unified three other seemingly disparate words, such as "mower," "atomic" and "foreign." Solving the puzzle required participants to think creatively, moving beyond the normal word associations--"lawn," "bomb" and "currency"--to come up with the more remote answer: "power."

Interestingly, induced happiness made the subjects worse at the second task, which required them to ignore distractions and focus on a single piece of information. Participants had to identify a letter flashed on a computer screen flanked by either the same letter, as in the string "N N N N N," or a different letter, as in "H H N H H." When the surrounding letters didn't match, the happy participants were slower to recognize the target letter in the middle, indicating that the ringers distracted them.

The results suggest that an upbeat mood makes people more receptive to information of all kinds, says psychologist Adam Anderson, co-author of the study published online by Proceedings of the National Academy of Sciences USA. "With positive mood, you actually get more access to things you would normally ignore," he says. "Instead of looking through a porthole, you have a landscape or panoramic view of the world."

Researchers have long proposed that negative emotions give people a kind of tunnel vision or filter on their attention, Anderson says. Positive moods break down that filter, which enhances creativity but prevents laserlike focus, such as that needed to recognize target letters in the second task, he says.

As for the myth of the depressed but brilliant artist, Anderson speculates that creativity may be a form of self-medication, giving a gloomy artist the chance to adopt a cheerful disposition.