The research was conducted as part of the project Science Live, sponsored by the Netherlands Organization for Scientific Research and the Royal Netherlands Academy of Arts and Sciences.

Some 481 test subjects participated in the research of Theo Gevers, PhD, and Albert Ali Salah, PhD. The researchers made a video recording of a posed smile and a spontaneous smile for each participant. The subjects also were asked to look angry, happy, sad, surprised, and scared. Gevers and Salah analyzed certain characteristics, such as how quickly the corners of the mouth turn upward. This knowledge can be applied to computer software that guesses ages, recognizes emotions, and analyzes human behavior.

The researchers also asked the test subjects to look at images of other test subjects. They had to guess the age of those people and state how attractive they found them. They were also asked to judge character traits, such as whether the person is helpful by nature, or if someone were perhaps in love.

The data collected allowed the researchers to develop software that can estimate people's age. The software takes into account whether someone is happy, sad or angry, and adjusts its estimate accordingly. The software appears to be slightly better at estimating ages than humans. On average, humans' estimates are seven years off, while the computer is six years off.

The research of Gevers and Salah also shows that you look younger when you smile, but only if you are older than age 40. If you are younger than 40, you should look neutral if you want to appear younger.