The year book, staple souvenir of any American school kid born in the last century is the subject of a study undertaken by university researchers into the way our smile has changed over time.

The study analysed almost 38,000 unique frontal-facing portraits taken from American high school year books to compile an impressive snapshot of each decade since the year 1900.

Because of the photographic typology of the portraits contained within they are perfect for computational data Continue reading →