Eye-centring common in 'selfie' photos

By Dr. Liji Thomas, MDSep 11 2019

Why bother whether one eye is nearer the center or not in an Instagram selfie? The question seems particularly unimportant. However, earlier research showed that in historic portraits, one eye is always nearer the center of the picture. Now a new study shows that most untrained Instagram selfie posters also create images with one eye more centered than the other, and more commonly the left eye. This could be because our eyes communicate the most information about our inner state with the viewer, through the direction in which one is looking and the focus of our gaze.

The present study was sparked by a debate as to whether the historical presence of eye-centering in portraits is an artefact, caused by unintentionally introduced factors, rather than a true finding.

How was the study done?

All photos were taken from the website http://www.selfiecity.net, and about 3,500 photos that passed the inclusion criteria were used. They originated in five major cities, New York, Sao Paulo, Moscow, Berlin, and Bangkok.

Standard selfies and mirror image selfies were classified separately. Standard selfies are taken at arm’s length with a digital camera (on a phone or a standalone device). On the other hand, a mirror selfie is a photograph of one’s mirror image and will include the camera/device in the photo as well. The latter tends to show more of the right cheek due to the display of the mirror image.

The most-centered eye was identified in each photo by finding the horizontal center of the photo (denoted by 0), and then measuring the distance of each eye from this center (between +0.5 and -0.5 depending on which side of the central line they are on, right or left). The smaller of the two was chosen. The average of two measurements was taken.

Criteria for measuring the relative position of the most-centred eye. The image was not in the examined database and was cropped for the purpose of illustrating measuring criteria. Image in the public domain (see www.pexels.com/photo-license). https://doi.org/10.1371/journal.pone.0218663.g001

What did the study show?

Most selfies showed that one eye was slightly to the left of the horizontal center of the photo. This is shown by the single peak of the histogram representing the distribution of the position of the most-centered eye. There was no significant difference in this trend by sex or city where the selfie came from.  There was also a significant trend towards choosing to center the left eye rather than the right.

Eye centering was seen in both mirror image and standard selfies. A leftward shift of about 1% is seen and its magnitude agrees approximately to that which would be expected from pseudoneglect, a phenomenon in which people observe the center of a line or an object not at the true center but rather at a point slightly to the left side of it. In other words, the left-sided tendency is more than could be attributed to random factors.

Moreover, the left eye is more commonly centered than the right. Most selfies show the left cheek in the photo.

This study concludes that both trained artists and untrained people tend to center one eye more commonly than the other, as part of the arrangement of the photo or painting. This is perhaps due to factors that influence our perception of what makes a picture balanced, and is not the product of rules that prevail in our cultures.

The distribution of the most-centered eye is less broad compared to that of the position of the nose or chin. It may be that it is more natural to choose one eye to center the photo composition on, because it shows the direction of gaze and indicates the state of attention. These are important indicators of the individual’s state of mind, and thus communicates a message which is the aim of both a modern selfie and a classic portrait from long ago.

Researcher Christopher Tyler comments: “The core result of this study was to replicate my earlier finding that painters tend to centre one eye in portraits, throughout the centuries, in a modern version of which the selfie takers are simultaneously both the artists and the subjects of the portrait.”

He also points out that this helps us understand how humans perceive symmetry and composition, in regard to picture framing. Moreover, humans may tend to use one particular feature as the center of the framed composition due to the presence of the fovea, a region at the center of the retina, which has the highest concentration of cones and thus the greatest sharpness of vision.

The study was published in the journal PLOS ONE on July 17, 2019.