unbelievable illusion

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 a couple of feet, and PRESTO!!
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 imag! e, 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??