What’s in a face? Quite a bit, when you ask a computer.
Computational facial recognition — which captures hundreds of attributes of facial structure — is used for everything from banking to border security. Researchers have now applied the technology to a small chalk sketch that may or may not portray an English queen who was famously beheaded for treason 490 years ago today.
In a study published in March in npj Heritage Science, scholars focused on a drawing, roughly 11 inches by 8 inches in size, that was completed in the 16th century by the artist Hans Holbein the Younger. The piece is part of a collection housed at Windsor Castle in England, and an inscription in its upper-left corner reads “Anna Bollein Queen.”
But there’s reason to doubt that the sketch portrays Anne Boleyn, said Karen L. Davies, an independent historian based in London and an author of the study. For starters, its inscription was added in the 18th century, long after the sketch was completed; inscriptions on other pieces by Holbein have furthermore been shown later to be incorrect. And the sketch’s chain of provenance is unknown; like many similar artworks, it circulated into private collections during times of political turmoil, Ms. Davies noted.
“It’s a little bit like having a family photo album that’s been passed around to different generations,” she said, “and photos have been taken out and put back in and they’ve gotten muddled up.”
Then there’s the subject’s appearance. The woman portrayed in the sketch is blonde, of a substantial build and shown with a double chin, whereas descriptions of Anne Boleyn consistently report that she was dark-haired and slender. “It doesn’t match the primary descriptions of Anne Boleyn,” Ms. Davies said.
To dig into this mystery, Ms. Davies and her colleagues, including David G. Stork, a computer scientist and electrical engineer at Stanford University, turned to computational facial recognition. “This has one foot in art history and one foot in computer science,” Dr. Stork said.
The team analyzed digitized versions of more than 80 Holbein sketches from Windsor Castle, the British Museum and the Louvre. Some of the individuals portrayed could be confidently identified, and some were known to be related to one another as siblings, parents or children.
The researchers estimated the degree of facial similarity between every possible pair of images. The algorithm that they used, which was originally trained on a data set of more than 15 million photographic images of human faces, detects patterns in facial structure that are far more subtle than features like hair color and ear shape. “The algorithm is actually calibrated to ignore these kinds of things,” said Hassan Ugail, a computer scientist at the University of Bradford in England and a member of the team.
Not surprisingly, the team found that family members tended to resemble one another more closely than did unrelated pairs of people. The researchers next compared their Holbein data set with a painting known to portray Anne Boleyn’s daughter, Elizabeth I. If the “Anna Bollein Queen” sketch was indeed of Anne Boleyn, they reasoned, the comparison with the Elizabeth I painting should reveal a facial similarity consistent with a mother-daughter relationship.
Instead, Ms. Davies and her collaborators found, the facial similarity was more indicative of a grandmother-granddaughter relationship — the sketch was more likely to depict Anne Boleyn’s mother than Anne Boleyn herself, the team concluded. That made sense, Ms. Davies said. The woman in the “Anna Bollein Queen” sketch is portrayed in domestic clothing rather than royal attire; some art historians have proposed that she might have been ill at the time. In fact, Ms. Davies noted, Anne Boleyn’s mother, Elizabeth Howard, was known to have been sick in 1536, around the time that Holbein completed the sketch. “We have documentary evidence that she was diseased,” she said.
It’s impossible to know why a likeness of Elizabeth Howard was misattributed as her daughter, Ms. Davies said. That sketches like these saw many owners may have contributed to the confusion. “These drawings have been through so many different sets of hands,” Ms. Davies said. The similarity in the women’s long, oval faces may also have played a role.
Amit Roy-Chowdhury, a computer vision scientist at the University of California, Riverside, who was not involved in the research, said that facial recognition can play an important role in art history. But going forward, he added, it will be important to assemble larger training data sets of faces in artwork, as algorithms trained strictly on photographs can introduce uncertainties. And that could be a challenge, since there are millions of faces in photographs but far fewer in art. “For artwork, you don’t have that many examples,” Dr. Roy-Chowdhury said.
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