I have a 4 year old lab. He's the happiest dog I've ever had, you just look at him and he starts wagging.
My daughter (she's an adult) comes to visit me and my wife every 6 months or so, my lab is in total love with her. As soon as she gets out of her truck he goes insane to get to her to love her up. I don't understand it. He's been like this since he was a puppy with her, she's the only one he'll lick, he licks her face, he sits on or beside her and follows her everywhere and waits by her door in the morning and goes crazy when she gets up. He loves us and is always happy but when she comes it puts him into a whole other world it's like he's euphoric. When she goes back home he mopes around for a day or so.
What could be the reason for that behavior?