Come Here Pigger
Actually, I've gotten my pigs to come to me- kind of.
If Frank sees me, he comes running. But this is probably because he wants food, not to see me or be pet. I don't know if he actually recognizes me, or assumes any huge thing on two legs is going to feed him. You don't necessarily have to feed them a treat everytime. Frank loves it when I hand-feed him hay.
If either Frank or Zoe hear me, they come running. The moment they hear me speak a certain way, they pop out of their pigloos to see if I am around. But this is also probably related to food. They do recognize voices. All you have to do is to assocaite your voice with food or something like that. My mom thinks I'm nuts, but sometimes, just sometimes, I talk to them while I feed or pet them.
As for letting you pet them, I don't know if you can train that. I suppose if you show them that you are nice and gentle, they won't freak out and run. My pigs let me pet them sometimes, and sometimes not. They pretty much choose. I usually start petting them on the bridge of their noses to the top of their heads very gently and that tends to warm them up for more.
And they do not always welcome me picking them up. Again, they kind of choose whether they want to be picked up. Some times they make it easy and some times, they just run. Sure they love plopping down on my lap and being pampered. But they don't always like the transition from being on the floor to being on the lap.
This is only from what I have found. If anyone has anything to add or any suggestions, please post them.