The Mona Lisa effect explained

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If you have ever watched Scooby Doo then you will be well aware that when there is a portrait painting on a wall, you must be cautious. The gang never seemed to realize but the bad guy often liked to spy on them through the eyes of a portrait painting as they walked around an old mansion. While it always seemed strange that the mysterious crew never realized they were being watched, it really wasn’t their fault. The reality is that since the invention of linear perspective in the 15th century, paintings have followed countless people. If the gaze of a painting has ever followed you around a room and you want to know why, read on.

The Mona Lisa is likely the most famous example but there are many others. Paintings were the central character’s eyes are locked on the audience have become popular since the 1400s. The idea is simple if the viewer stands in front of a picture the subject of the painting is looking directly at them. If the viewer moves to the left or right, the subject continues to follow them. 

The strange phenomenon is technically called ubiquitous gaze but is referred to by many as the Mona Lisa effect. It is caused by the desire of artists to create a 3D image on a 2D painting. In effect, the painter wants to create depth in the picture. In the Mona Lisa, for example, there is a countryside setting in the background with the central character in the foreground. Through the use of linear perspective, the illusion of depth is created.

Linear perspective works through the use of vanishing points. Lines that travel from the foreground of the picture towards the background. Everything on these lines gets smaller as they approach the background. All lines then travel in parallel to these vanishing point lines. This usually results in the eyes of the central character being at the very front of this picture. If this technique is used and the character’s eyes are looking straight ahead it will create a ubiquitous gaze. If the gaze is plus or minus 5 degrees from straight the gaze will still work, any more than that and, in theory, it will appear that the character is never looking at anyone. No matter when you look from the character will always be looking to the right or left of you. 

This powerful technology means that even though you are looking at a flat surface you get the impression of depth. Due to linear perspective, the near and far points of the painting will remain near and far no matter where you view the picture form. 

Filippo Brunelleschi is often heralded as the creator of linear perspective although it is likely that Roman and Greek artists did use it but that it was never popularized. In modern-day, the technique is now widely used.

While many people refer to this as the Mona Lisa effect, they shouldn’t. The strange reality is that Mona Lisa actually doesn’t have a ubiquitous gaze. The portrait of the woman with an amazing smile actually captures her looking 15.4 degrees to the right. This is too great to have the appearance of always looking at you. It does still use linear perspective it is just that she is always looking to the right. This makes people feel the Mona Lisa is always almost looking at them or perhaps over their shoulder, no matter where they stand. Perhaps this slightly greater angle is found to be even more alluring and awkward by the viewer as no matter where they stand, Mona Lisa is always almost looking at them. Maybe this is part of the explanation of how so many people have been drawn to the picture for so many years.