12 or 13 Mens Illusion

Here we have an animated gif file. If you look closely you can count 12 little people. After the gif slides the image around you end up with 13 little people. How does this happen?If anybody solve this mystery please comment me.

This is really easy. The key is to look at every part attentively.

You see, this GIF is like a three pieces puzzle. Two on the top, one at the bottom.
Let's say the pieces on the top are X and the one at the bottom is Y.
The top piece with 7 body parts is 1-a and the top piece with 5 body parts is 1-b.

X-a : 7 body parts
X-b : 5 body parts
Y : 12 body parts

X-a + X-b = 12 body parts.

So it means that every body parts in X have to replace one body part in Y.

If you look carefully, you can see the missing hair and the incompletely feet on the left side of image when X-a switches with X-b. It mean that the one who is missing 1/2 of his feet (who is supposed to replace the missing hair one) replaces no one.

Huh ? I don't understand !

Oh, ok.

Sweet a écrit:

Huh ? I don't understand !

There are two pieces that aren't replacing any piece.