Written by Emily Dixon, CNN

The Mona Lisa is famed for two things: her enigmatic smile and her steady gaze, widely believed to follow her viewers around the room.

Indeed, Leonardo da Vinci's world-renowned painting, also known as "La Gioconda," inspired the name of a scientific phenomenon: the Mona Lisa effect, or the perception that the subject of an image is always looking directly at you, no matter where you stand.

But according to research by scientists from Germany's Bielefeld University, published in the journal i-Perception , there's one painting that definitively doesn't demonstrate the Mona Lisa effect: the Mona Lisa herself.

In fact, the researchers say, the subject of the painting is actually looking about 15 degrees to your right -- at your right ear, perhaps, or over your shoulder.

Gernot Horstmann, an associate professor at Bielefeld University's Center of Excellence - Cognitive Interaction Technology (CITEC), and Sebastian Loth, a research assistant, asked 24 participants to assess the gaze of the Mona Lisa. Instead of simply asking each participant whether they felt the Mona Lisa was looking at them -- a binary response likely to be influenced by existing beliefs -- they displayed the painting on a computer screen, and asked the participants to measure the direction of the gaze on a two-meter (6.6-foot) carpenter's rule placed horizontally between them and the screen.

A doctor recently diagnosed the Mona Lisa with a potential thyroid condition.

The distance between the participants and the computer screen remained the same, at 66 cm (26 inches), but the ruler was moved both closer to and further away from the screen throughout the trial. The researchers also altered the size and visible area of the Mona Lisa to determine whether the perception of her stare was influenced by particular elements of her face. The participants were asked to respond to the painting at various degrees of zoom, between 30% and 70%, and saw crops that only included her eyes and nose, as well as others that showed her whole head.

To avoid the participants settling on the same measurement on the ruler every time, Horstmann and Loth also showed them the Mona Lisa moved 3.4 cm (1.3 inches) to the left and right.

Previous research cited in the study indicates the range of the Mona Lisa effect: the subject of an image will appear to be looking at its viewer if its gaze is within 5 degrees to the left or right. The gaze of the "Mona Lisa," however, was measured by the study participants at an average angle of 15.4 degrees to the right -- in short, the Mona Lisa is definitely not looking at her audience.

"There is no doubt about the existence of the Mona Lisa effect," Horstmann and Loth concluded. "It just does not occur with Mona Lisa herself."