A sex therapist was doing research at the local college when one of the male volunteers told him: "When I get it in part way, my vision blurs. And when I get it all the way in, I can't see a thing.©JOKEDEMO.COM

"Hmmm"and#59098;hat's an interesting optical reaction to sex," said the researcher. "Would you mind if I had a look at it?"©JOKEDEMO.COM

So the volunteer struck out his tongue.