That painting above, of the Madonna and child? Art experts have always suspected that Italian Renaissance master Pietro Perugino didn’t paint it entirely by himself. But they were never entirely sure.

Now a team of Dartmouth professors say they’ve mathematically proved that several different people worked on the painting. They developed a technique in which they digitize the painting into a huge 16,852-by-18,204-pixel photo. Then they took the faces of the six people in the painting, and broke them into several hundred sections, 256 by 256 pixels in size. Then, as Wired News reports:

The filtered images were then run through a series of algorithms, the results of which produced a set of numbers. The more similar the painting style, the closer together those numbers were. Once those numbers were plotted on a graph, the Dartmouth team found that points representing the faces on Madonna and two of the saints were crowded together tightly. Baby Jesus and the two other saints — those three were far, far apart. So the researchers believe that one artist painted Madonna and one canonized pair, while three other artists composed the remaining faces.

Art scholars are dubious that the technique is useful, but personally, I’m intrigued by it. It seems like an interesting literalization of the brain’s statistical data-processing equipment. We humans are incredibly good at knowing when faces just don’t quite match up or don’t seem quite right. Though the scientists have picked a bunch of obviously arbitrary mathematical markers, the idea of data that doesn’t “match up” seems like a neat metaphor or analogue for what the brains of art experts are doing when they look at the paintings: They’re crunching the patterns, comparing them to the enormous database of all art they’ve seen before, and detecting something — oh so subtle — amiss.

(Thanks to Noah Shachtman for this one!)