Editor's Note: This story was updated on Friday Dec. 11 at 2 p.m. E.T.
People now may have more to smile about — at least when it comes to their yearbook photos.
High school seniors today are much more likely to smile for the camera in their senior- year snaps, compared with the turn of the 20th century, new research finds.
Not surprisingly, sartorial choices have changed as well. Few young women now would contemplate shellacking their hair into a beehive, instead opting for longer, more natural locks, said study lead author Shiry Ginosar, a doctoral candidate in computer science at the University of California at Berkeley. [Smiles Secrets: 5 Things Your Grin Reveals About You]
People also tend to go for a less dressy look, perhaps reflecting changes in how rare it was to get photographed.
In the early 1900s, "it was a really big deal to get your picture taken and so people really dressed up for it, with hats and everything," Ginosar told Live Science.
To see how the images of people had changed over the years, Ginosar and her colleagues used a computer-face-recognition program to analyze 37,921 yearbook photos dating from 1905 to 2013. The 949 yearbooks came from 128 schools and 27 states.
In the earliest photographs, serious expressions ruled the day. Photos took such a long time to capture that women often had headrests so the photo wouldn't turn out blurry, Ginosar said.
"In the late 19th century people posing for photographs still followed the habits of painted portraiture subjects. These included keeping a serious expression since a smile was hard to maintain for as long as it took to paint a portrait," the researchers wrote Nov. 9 in the preprint journal arXiv
At that time, it was also considered better to have a small mouth, so people would say "prunes" rather than "cheese" in a photo, the researchers wrote.
But once amateurs began using their personal cameras, smiles became the norm, according to a 2005 study in the journal Critical Studies in Media. In part, that was because the Kodak Corp. used its advertising to inspire people to photograph every happy occasion, from that first birthday party to the family vacation at the Grand Canyon, the researchers wrote. By the 1940s, most people smiled big for the camera in their high school photos.
Hair through the ages
Women's hair also went through a dizzying array of (arguably regrettable) fashions. Women veered from the finger waves of the 1930s to the bobs, flips and bubble cuts of the 1960s, to the teased bangs and perms of the 1980s. Men have typically kept their hair short, except during the 1970s, when Afros and slightly longer hair prevailed, Ginosar said.
For the last few decades, longer, straighter hairstyles have been the norm for girls.
This may be a trend toward a lower maintenance look, Ginosar said.
"I have no idea how people actually got their hair to stay up in the '60s — whether it was with rollers or with hairspray — but it definitely seems that in the 2000s a lot of people just left their hair down and had it pretty natural, not even a lot of bangs."
In general, the gradual move toward a more low-key look may reflect a change in who takes yearbook photos and why. In 1905, photos were pricy and took forever to take. Most people left school before their senior year in high school, and only the elite of the elite could afford to get their mug immortalized, Ginosar said. Getting a yearbook photo snapped was a big deal, so people got dolled up for the occasion.
"In the 1900s, I have pictures of girls who showed up with fur and pearls — the real deal, stuff that somebody in high school wouldn't even own these days," Ginosar said.
Women look much less dolled up in later photos. For men, things changed less. Suits have been a near uniform for men — except in the 1970s, when "wide turtlenecks" were popular, Ginosar said.
While smiles are almost mandatory now, the ability to snap a million selfies and post them instantly on apps like Snapchat and Instagram may eventually change the conventions for portrait photos, Ginosar said.
For instance, researchers have found that the average selfie is not a smiling one, and the photograph angle is totally different from a typical yearbook photo, Ginosar said.
So perhaps in 20 years, yearbook photographers will take their photos from above, ask people to look up at the camera and make their best pouty duck face.
Editor's Note: This story was updated to correct the spelling of Shiry Ginosar's name in two instances.