Children with the brightest smiles in family photographs are more than three times likely to have a successful marriage than those who frown, according to research.
According to scientists, even photos taken of family outings when the child is as young as five can show a glimpse of the future.
The researchers asked almost 650 adults for pictures taken during their final year school and rate the brightness of their smiles.
The scientists, from DePauw University in Indiana, also asked the volunteers, between 21 and 87, whether they had ever been divorced, and subsequently matched their answers with the data on their smiles.
"Smile intensity predicted whether or not participants divorced at some point in their lives," the researchers said, adding: "The less intensely participants smiled, the more likely they would be divorced later in life."
It found that those with the weakest smiles were more than three times as likely to have been through a divorce, according to the journal Motivation and Emotion.
A second experiment, which included pictures taken of people as young as five, backed up the conclusion.
The researchers believe that those who are generally happier are therefore more likely to try to work through difficulties in relationships and marriages.
They also believe that those who are happy types may marry companions who reflect their own sunny disposition.