Does anyone know how it works?
Amazing!!!
(Sorprendente !!!: Mira a la derecha el tipo jovial y a la izquierda el malhumorado. Párate y saparate unos seis pasos de la computadora, mira las imágenes de nuevo: han cambiado de lugar ) 
If you watch the above images from your seat in front of the computer,
Mr.Angry is on the left, and Mrs.Calm is on the right.
Get up from your seat, and move back about eight feet!! They switch places!!
I believe this illusion was created by Phillippe G. Schyns and Aude Oliva of the
Univ. of Glasgow
This proves that we may not be seeing what's actually there, all the time!!
I do not know how they generated this fascinating image, and I believe no-one
else is able to generate anything similar in Photoshop. I know it has something
to do with "low-pass" and "high-pass" filters, but the details??
-cw-