Daniel Tomasulo explains why a bigger smile that extends to your cheeks, eyes and the crow's feet around them (known as a Duchenne smile) is more genuine than one that doesn't, and what that implies for your future happiness:
In the longitudinal study of Mills College graduates, Keltner and colleague LeeAnne Harker coded the smiles of 114 women who had their university yearbook photo taken sometime during 1958 and 1960. All but three of the young women smiled. However, 50 had Duchenne smiles and 61 had non-Duchenne, courtesy smiles.
The genuine smile group were more likely to get and stay married, and had higher score evaluations of physical and emotional wellbeing. Remarkably, Keltner’s study was able to find this connection more than 30 years after the college photos were taken.
This doesn't bode well for Nicole Kidman.