Two

If you cross your middle and index fingers
and touch them both to the tip of your tongue,
it feels like you have TWO tongues.

Try it.
.

Update: Perhaps you all are simply more evolved than primative circleinasquare. For me, the effect is amplified by slowly running the tip of my tongue over the crossed fingertips, and DON'T look at your fingers or reflection.

I can't stop.