Originally added on 5th July 2009

Last updated on 17th March 2012

I do think that Matt Hertenstein and colleagues came up with an eye catching title here:

Hertenstein, M., C. Hansel, et al. (2009). "Smile intensity in photographs predicts divorce later in life." Motivation and Emotion 33(2): 99-105. [Abstract/Full Text] [Free Full Text]

Abstract: Based on social-functional accounts of emotion, we conducted two studies examining whether the degree to which people smiled in photographs predicts the likelihood of divorce. Along with other theorists, we posited that smiling behavior in photographs is potentially indicative of underlying emotional dispositions that have direct and indirect life consequences. In the first study, we examined participants' positive expressive behavior in college yearbook photos and in Study 2 we examined a variety of participants' photos from childhood through early adulthood. In both studies, divorce was predicted by the degree to which subjects smiled in their photos.

Obviously there are many other factors also involved in whether someone will get divorced or not! However the effects were pretty strong with the 10% with most intense smiles only having a fifth the chance of getting divorced compared with the least smiling 10%. Other research has pointed in the same sort of direction, so Sonja Lyubomirsky and colleagues have argued convincingly that greater happiness is not only caused partly by doing well in different areas of one's life, it is also a cause of doing well in different life areas - including relationships. There's also the "associative mating" argument - happy people tend to marry other happy people. There's the finding that, when interpersonal difficulties do arise, optimists seem more able to sort things out constructively - seeing things positively can often make them more likely to be so. And even research showing that emotions are "infectious".

Actually Hertenstein's main research work is more on touch than on smiling. See his "Touch and emotion lab" with its useful series of fascinating freely downloadable full text research studies including one I particularly like entitled "The communicative functions of touch in humans, non-human primates and rats: A review and synthesis of the empirical research".

Since first writing this blog post a further fascinating research study has emerged: