"Guess Who" joke

A young man excitedly tells his mother he's fallen in love and
>going to get married. He says, "Just for fun, Ma, I'm going to
bring
over
>3 women and you try and guess which one I'm going to marry."
>
>The mother agrees.
>
>The next day, he brings three beautiful women into the house and
>sits them down on the couch and they chat for a while. He then says,
>"Okay, Ma, guess which one I'm going to marry."
>
>She immediately replies, "The one in the middle."
>
>"That's amazing, Ma. You're right. How did you know?"
>
>"I don't like her."