I just visited my favorite psychology blog, BPS research, and found a really cool study of smiling. The researchers rated the "smile intensity" of 230 baseball professional baseball players and "The researchers used a three-point smile scale: no smile, half smile (mouth only), and genuine 'Duchenne' smile (muscles contracted around the mouth and corners of the eyes)." They found:Focusing on the 150 players who'd died by the time of the study and controlling for extraneous factors such as BMI and marital status, the researchers found that those who were flashing a genuine 'Duchenne Smile' were half as likely to die in any given year compared with non-smilers. Indeed, the average life-span of the 63 deceased non-smilers was 72.9 years compared with 75 years for the 64 partial smilers and 79.9 years for the 23 Duchenne smilers.
The question, of course, is does smiling make you healthier, being healthier make you smile more, or perhaps most likely, a smile is a sign of an unpbeat personality, which has been linked to longevity in numerous studies -- check out this cool study of nuns in particular. But there is also a fascinating set of studies that show smiling makes you feel happier and frowning make you feel grumpy. I wrote about this in fairly gory detail in one of my early blog posts in 2006. The "mechanism" through which this apparently happens is really cool. Smiling leads to momentary cooling of blood the brain and frowning leads to momentary heating -- and a large body of research shows that being "hot-headed" makes people grumpy and aggressive.
I love this weird emotion stuff. It seems like a smile might be good for us -- or perhaps more likely, is a sign of a good mental health.
P.S. The picture is of baseball great Willie Mays, I think it is from 1952 and that looks like a real smile to me. Mays is still alive, by the way.
P.P.S. The citation for the study is: Abel, E., & Kruger, M. (2010). Smile Intensity in Photographs Predicts Longevity. Psychological Science