My burm can tell the difference between people. Would only bite my ex (smart snake hence the EX part). She also greets me at the doors to her cage when I come in the room, but doesn't do it with anyone else.
As for retics, I don't currently own any, but those I have dealt with were intelligent. However gauging intelligence in snakes is tough I think, because what do you have to compare it all to? To say that retics are more alert and in tune...maybe