Effect of IAD on perceived mutual gaze.
Two-dimensional portraits generate a strong perception of eye contact. I remember the posters of rock stars in my friend’s room when I was a kid. When I walked around in the room, Alice Cooper’s gaze appeared to follow me. The phenomenon, known as the Mona Lisa effect, is well studied and documented. However, as we discovered in a recent study
, the Mona Lisa effect is not the only phenomenon that explains the magic-like appeal of two-dimensional portraits of rock stars and enigmatically smiling ladies.
As a model poses for the photographer, they often look directly in the lens of the camera; eye contact (mutual gaze) creates captivating photographs. When an observer then looks at the resulting two-dimensional image, both eyes of the observer receive a direct gaze. This condition is in contrast with a natural setting where people look at either the left or the right eye of each other at a time. Thus, the two-dimensional photograph or painting provides a perception of eye contact that is stronger than possible in a three-dimensional real-life setting.
The implications of the results are manifold; two-dimensional portraits are widely used in emotion and gaze research. However, our results indicate that using two-dimensional portraits reduces the ecological validity of the results, i.e., the results may not apply in real-life situations. The results were published in the open-access journal Journal of Vision
That is the question we set out to solve in our study whose results were published earlier this month in Springer’s journal 3D Research. The obvious reason is the chicken and egg problem: people do not have stereoscopic 3D displays. But what if they had? We gave five novice participants 3D cameras and displays for four weeks and let them use the cameras as they liked.
The number of photographs with excess disparity fell about 70% during the four weeks. The number of photographs taken each week varied only little.
The participants took a total of 699 photographs during the trial. Each week, they answered a series of questions, evaluated their attitudes towards the photography, and chose the best and worst photographs. After the trial we conducted a thorough exit interview with each participant individually. In addition to the participants’ responses, we analysed the photographs by computing the disparity maps by matching the local features (SIFT
) in the stereo pairs.
Turns out that the participants encountered several problems during the experiment. The main problem was that they took photographs at too close distances in the beginning of the trial. The distance between the lenses in the camera used in this trial was 7.5cm, which creates too large disparities in the photographs taken at normal indoors conditions. Photographs with excess disparity are extremely unpleasant to look at, and in a real use situation the initial disappointment would likely have led to the camera gathering dust on a shelf. The participants did, however, learn to avoid the excess disparities. They also commented that people in the photographs looked unnatural. Other issues were caused by the camera flash and objects at the edges of the photograph. Check out the full article for further details. Thanks to Nokia Research Center for collaboration in this project.