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Photo Distance Represents Trustworthiness

In a finding that is of particular importance when combined with various attempts to create a personalised avatar by mapping photos of your own face to it, University of California researchers have discovered that the distance between the photographer and the subject is crucial to the trustworthiness of the resulting picture.

That's all very well and good for still photos, but if the result is intended to be used as an interactive avatar head – the one you interact through all the time in a virtual environment, then that trustworthiness is critical.

Pietro Perona, the Allen E. Puckett Professor of Electrical Engineering at Caltech, came up with the initial idea for the study. Perona, an art history enthusiast, suspected that Renaissance portrait paintings often featured subtle geometric warping of faces to make the viewer feel closer or more distant to a subject. Perona wondered if the same sort of warping might affect photographic portraits—with a similar effect on their viewers—so he collaborated with Ralph Adolphs, Bren Professor of Psychology and Neuroscience and professor of biology, and CNS graduate student Ronnie Bryan to gather opinions on 36 photographs representing two different images of 18 individuals.

The photographs were taken in pairs for each subject. One photograph was taken at close range, and the other was taken from a distance of seven feet from the subject's face.

"It turns out that faces photographed quite close-up are geometrically warped, compared to photos taken at a larger distance," explains Bryan. "Of course, the close picture would also normally be larger, higher resolution and have different lighting—but we controlled for all of that in our study. What you're left with is a warping effect that is so subtle that nobody in our study actually noticed it. Nonetheless, it's a perceptual clue that influenced their judgements."

That same warping will of course be present when the image is wrapped to a 3D avatar's face, and quite probably distorted further by it. It is a subtle effect, but one which had a psychological influence on the study participants. When shown a random sampling of shots, with no fore-knowledge of whether they were looking at a shot taken close up, or from some distance, there was, the researchers discovered, a clear bias present. The shots taken at close range were judged less trustworthy individuals, than those taken at a distance of seven feet.

"This was a surprising, and surprisingly reliable, effect," says Adolphs. "We went through a bunch of experiments, some testing people in the lab, and some even over the Internet; we asked participants to rate trustworthiness of faces, and in some experiments we asked them to invest real money in unfamiliar people whose faces they saw as a direct measure of how much they trusted them."
Across all of the studies, the researchers saw the same effect, Adolphs says: in photos taken from a distance of around two feet, a person looked untrustworthy, compared to photos taken seven feet away. These two distances were chosen by the researchers because one is within, and the other outside of, personal space—which on average is about three to four feet from the body.

In some of the studies, the researchers digitally warped images of faces taken at a distance to artificially manipulate how trustworthy they would appear. "Once you know the relation between the distance warp and the trustworthiness judgement, you could manipulate photos of faces and change the perceived trustworthiness,'' notes Perona.

This will hopefully mean that at a future point, the research will result in an expert system able to analyse a photograph you take of yourself, and look for signs of psychological warping – before you apply it to your avatar.

For now though, a photograph taken at a distance, is going to be far more reliable, than one taken in your own outstretched hand – or by a photo booth.


Ready for Your Close-Up?

Perspective Distortion from Interpersonal Distance Is an Implicit Visual Cue for Social Judgments of Faces (Paper)

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