The answer, as found in a new study, is actually pretty obvious.
According to a study that involved showing participants photos of people of varying ages, you look younger when surrounded by older people. Conversely: you look older when hanging out with youngsters, of which Hugh Hefner is glaring proof.
The researchers asked 24 young adults to look at pictures of 15 female and 15 male faces. Each image was doctored to show what the person would look like in his or her 20s, 30s, 40s, 50s, 60s and 70s.
The volunteer were systematically wrong at estimating other people's ages after they had looked intensely at faces of people of a specific age group.
For example, if many faces of elderly people were shown on the computer first, followed by the face of a middle-age person, the volunteers made out the middle-age person to be substantially younger than he or she was. But after first studying younger faces, the volunteers estimated the middle-age person as being substantially older.
This is all very well, but in my experience, the times when I'm most surrounded by older folks — ie, at nursing homes or volunteering at senior events — are some of the last times when you'd want to look younger, be it for romantic or professional purposes. On the other hand, for those who want to really put this advice into effect, there's an obvious means.