Put two normal looking person on left and right. Put a cross between them. Do it for a few pairs of people. Ensure that the eyes are aligned properly. Now that is Flash Face Distortion, and the effect is disturbing. Watch it yourself.
Here is the disturbing video if you focus on the cross.
Here is an abstract of what is going on.
We describe a novel face distortion effect resulting from the fast-paced presentation of eye-aligned faces. When cycling through the faces on a computer screen, each face seems to become a caricature of itself and some faces appear highly deformed, even grotesque. The degree of distortion is greatest for faces that deviate from the others in the set on a particular dimension (eg if a person has a large forehead, it looks particularly large). This new method of image presentation, based on alignment and speed, could provide a useful tool for investigating contrastive distortion effects and face adaptation.