It's a "scientific legend": that Mona Lisa's eyes follow you wherever you go, a phenomenon so well known that it birthed the term "Mona Lisa Effect." Except it's not true, at least in the case of Leonardo da Vinci's painting. That's the conclusion of two researchers from Bielefeld University's Cluster of Excellence Cognitive Interaction Technology. The effect itself "is undeniable and demonstrable," says Dr. Sebastian Loth, per a press release. But the result of more than 2,000 assessments of her gaze found that not to be the case. To facilitate the study, published in the journal i-Perception, 24 test subjects were seated in front of a computer screen showing the Mona Lisa and told to look at a folding ruler and say which number her gaze was directed to.
The ruler was placed at two different distances between the participants and the monitor, and different sections of the portrait were used (i.e., some the full painting, some with just her eyes and nose, at various image zooms). An analysis of the resulting responses found that, overwhelmingly, the impression is that her gaze wasn't straight-on, but landed to the viewer's right-hand side. "More specifically, the gaze angle was 15.4 degrees on average," says Dr. Gernot Horstmann, dubbing the Mona Lisa Effect "nothing but a misnomer." He explains that the effect holds "if the person portrayed looks straight ahead out of the image, that is, at a gaze angle of 0 degrees." The effect can come across if that gaze angle widens slightly, up to about 5 degrees, "but as the angle increases, you would not have the impression of being looked at." (A doctor claims disease shaped Mona Lisa's smile.)