Do you understand that along with happiness, in the exact same way and in perfectly equal proportion, man also needs unhappiness.
-Fyodor Dostoevsky (1872), The Possessed
Positive psychology theory and research have helped dispel the long-standing "happy and stupid" stereotype. From Fredrickson's broaden-and-build theory of positive emotions to the important literature review by Lyubomirsky, King, and Diener linking life satisfaction to positive outcomes in many important domains of life, we now have solid grounds for concluding that feeling good has desirable consequences.
A paper by Simone Schnall, Vikram Jaswal, and Christina Rowe, published in 2008 in Developmental Science, therefore deserves attention because it is at odds with this conclusion. Two experiments with children were reported.
In the first, 10-11 year-olds listened to looped segments of music, either a piece known to induce a happy mood or a piece known to induce a sad mood. (A manipulation check verified the intended effects). Then all the children were given an embedded figures task, performance on which reflects attention to detail. Children in a happy mood performed worse than children in a sad mood.
In the second, 6-7 year-olds were shown brief video clips that induced happy, neutral, or sad moods. (Again, a manipulation check verified the intended effects). As in the first study, all were tested on an embedded figures task. Children in a happy mood performed worse than those in the other conditions, who did not differ from one another.
Before the media gets hold of these results and reports them under a misleading headline (e.g., "Why Grief Is Good" - Newsweek, 2008), let us put the research--which I hasten to say is well-done, interesting, and important--in context.
First, these studies do not show that happy children are bad students. We already know that they are not. Furthermore, we also know that happiness is associated with more creative thinking, which Schnall and colleagues acknowledged. Attention to detail is an important skill, but it does not exhaust the skills that lead to good academic performance or success at life.
Second, these studies do not show that sad children are good students. No way.
Third, more generally, these studies do not necessarily speak to happiness or sadness as traits. The research is about what psychologists call states, temporarily induced moods.
The results show that a happy mood can have costs in certain circumstances, specifically those in which attention to detail is required.
Why am I going on and on? I want to head off rampant generalization of these findings, especially by those in the media who get an apparent kick out of sadness, depression, and pessimism, and studies showing that they can have benefits in certain circumstances (just as happiness, zest, and optimism can have benefits in other circumstances).
Positive psychology is sometimes criticized for urging relentless cheerfulness and happiness on people. I do not think any responsible positive psychologist does this, but regardless, let's not over-react in the other direction by using studies like this one to justify sadness or glorify depression.
My even-handed recommendation is that people be encouraged to take charge of their moods and adjust them according to the demands they face. Don't proof-read your dissertation or check your 1040 calculations when you are giddy. And don't try to plan profound changes in your life or brainstorm new projects when you are sad.
Fredrickson, B. L. (2001). The role of positive emotions in positive psychology: The broaden-and-build theory of positive emotions. American Psychologist, 56, 218-226.
Lyubomirsky, S., King, L. A., & Diener, E. (2005). The benefits of frequent positive affect: Does happiness lead to success? Psychological Bulletin, 131, 803-855.