Tricks are for Kids

Ok, this a trick. It's wriitten in porgegese so I'll translate. If you stare at the black dot for a long time, the gray will disapear.

The second trick,(it's written in porgegese too.) it asks "How many legs does this elephant have?"

The third trick asks "How many black dots are there?"
Finally, the last one, it asks "Are these lines strait?"