The graphs summarizes an analysis from a database of high school yearbook photos.
Ginosar et al. have only one explanation for the upward trend – technology. In the early 20th century, they say, photo portraiture was still under the influence of 19th century technology. Those old cameras required an exposure of several seconds, sometimes as long as half a minute. When you have to be motionless for that long, a neutral expression is easiest to maintain. . . .
The trouble with this explanation is that the Kodak camera was introduced in 1888. By 1900, everyone was taking snapshots rather than posing solemnly for photographs taken by a man hiding under a black cloth with a large wooden box on resting a tripod. The snapshot was to 1903 what the selfie was to 2013. But perhaps old poses hang on even though they are no longer technologically necessary, and fashions in yearbook poses diffuse gradually.
But why the decline in smiles from 1950 to 1965? These were, by some accounts, the most contented years of the century, free of conflict and turmoil, even boring. . . . I [Livingston] have no idea. You lovers of zeitgeist explanations, feel free to speculate.
I wish they’d shown the data for every year. The patterns are smooth enough that it seems wasteful of information to bin into 5-year categories.