The likelihood of smiles and the duration of smiles increased with age; attribute this to greater expression of positive emotion in older people; women smiled more than men over all

Faded Smiles? A Largescale Observational Study of Smiling from Adolescence to Old Age. Daniel McDuff & Stephanie Glass. IEEE Transactions on Affective Computing, https://ieeexplore.ieee.org/abstract/document/8735803/

Abstract: A relatively large body of work exists examining sex differences in expressiveness; however, there remains little research of differences in expressiveness associated with aging. Observational studies of facial expressivity across ages are limited in part due to the poor scalability of traditional research methods. We collected over 17,000 videos of natural facial behavior using the Internet and performed a large observational study of smiling responses of people ages 18 to 70 years. Using automated facial coding we quantified the presence of smiles as people watched a set of controlled mundane online content. The likelihood of smiles and the duration of smiles increased with age. We attribute this to greater expression of positive emotion in older people. Women smiled more than men over all and gender differences increased significantly with age. We question whether results may be influenced by the effect of age on the accuracy of the automated smile detection; however, validation on a large set of human coded videos shows that the observed effects were not due to smile detection performance.

Keywords: Smile Detection, Aging, Large-scale, Psychology