That’s Rembrandt’s engraving The Three Trees on the left, and its mirror image.

Art historian Heinrich Wölfflin found that reversing the image produces a distinctly different aesthetic effect. In the first image, “the group of trees at the right gives an impression of energy”; in the second, “the trees are devaluated and emphasis now seems to rest on the flat, extended plain.”

But curiously, writes Chris McManus in Right Hand, Left Hand, “although ordinary viewers say [such reversals] look different, they cannot reliably decide which is the original and which the mirror-image, unless they have seen the picture before.” Whom can we credit for the second composition?