Friday, July 8, 2011

Not tricks, Michael, illusions.

I have to share this amazing visual illusion with you.

Sean Murphy, an honours student in our lab, was playing around with some faces for an experiment. He aligned the faces at the eyes and then started flicking through them. He was shocked by the ugly faces staring back at him.

We called it the Flashed Face Distortion Effect. But we don’t yet know what causes it.

The effect might have something to do with relative encoding. That is, forcing people to encode each face in light of the others. By eye-aligning the faces, it becomes much easier to compare their shape and the relative location of their features, so the differences between them become more evident. And it’s most certainly related to work on adaptation, and the face distortion after effect specifically.

You can read more about it here and request a copy of the paper here. I hope you find the effect as jaw-dropping as I do!


Tangen, J. M., Murphy, S., & Thompson, M. B. (2011). Flashed face distortion effect: Grotesque faces from relative spaces. Perception advance online publication, doi:10.1068/p6968


  1. Amazing discovery, maybe you can make a correlation with the fact that many people finds a partner more atractive when in contrast with other people.

  2. Very interesting and the serendipity makes it even tastier. For some reason it brings to mind Primary Auditory Stream Segregation in which a stream of sounds, which vary in their frequency, is at first perceived as one stream but at higher rates or frequency differences the ear/mind splits it into separate streams.

  3. Run the video in full-screen mode. Hide the left part of the screen, and keep your eye on the cross-mark. The effect still occurs.

  4. I still see the oddball faces even with one side covered. It doesn't seem to rely on their being two pictures, just having the eyes focused to the side of the picture of the face.

  5. I believe it has nothing to do with the real-time comparison of the juxtaposed faces, but rather with the effect of after-image vs the brain's processing of the image. Your brain is trying to make the subsequent face "make sense" with the one before it. The result is a cartoonish combination of the dissimilar faces. I believe the effect would be enhanced by putting the most dissimilar faces in series (particularly male/female or large/small). There may also be an optimum speed whereby the brain cannot recover effectively. There also seems to be a fatigue factor, where the effect becomes more exaggerated the longer the brain has to try to compensate. I have also noticed that while keeping eyes on the cross, the effect can be lessened if one mentally concentrates on one particular side or the other, so there is an inattention or unconscious factor too. So, I do think having the two faces side by side creates a difficulty for the brain in subconsciously processing the two images at once, making the effect more pronounced. Fascinating!

  6. I agree. The effect seems dependent on the after-image effect versus the brain's attempt to reconcile the subsequent face with the one before it. There is also a fatigue factor where the distortions seem to become worse with time. Also an inattention/subconscious factor: if you keep eyes on the cross, but mentally concentrate on one side or the other, the effect is diminished. It may be that forcing the brain to look at pairs at the same time, enhances the effect by preventing concentration on one or the other. I wonder if there is also an optimum speed factor, maximizing use of the brain's after-image/recovery gap, if there is such a thing. Fascinating!