My Shelby is a real sweetheart. She learns commands very quickly because she pays close attention to me and is very motivated by almost anything: games, food, toys, praise, petting, whatever's available. She'd know dozens of tricks if I had the will to teach them to her. I brought her home when she was eight weeks old and started teaching her to sit for her food almost immediately. In just a couple days, she would walk up to anyone eating a snack in the kitchen, walk around to the front of them, and sit, looking up angelically. My mother could never resist that, which only encouraged her even more. Now she'll do other things for a treat: speak, roll over, shake, give five. If I hold up a treat and ask her "What's one plus one?", she'll bark twice. I can balance food on her nose, and she'll hold still until I tell her okay, when she'll toss the food up into the air and catch it about eighty percent of the time. I had her balancing eggs on her nose (cooked ones) around Easter this year, which was much harder for her because they can roll off. Also, she can't eat them, so I'd have to take them off her nose and just feed her a treat.
I've read that dogs that were bred to work WITH humans tend to be more attentive to what people want from them than breeds that were developed to work seperately from humans. Herding breeds like Shelties and German Shepherds, or Sporting breeds like goldens and labs, are therefore the most trainable. Hounds and terriers, on the other hand, are more "independent". Also, some breeds pay more attention to what's going on around them. Border Collies, who are considered the most trainable breed of all, are also known to be extremely active and excitable. We used to have a Border Collie, and ANYTHING that moved could put him into a frenzy. He was just superalert to everything. A dog like that probably would learn quickly, just because he's not likely to miss very much. My Sheltie's like that too, but not quite to the same extent. Still, it's not difficult to get her worked up. I had her in obedience classes as a pup, and at one thing we practiced was playing with our dog and getting the dog to settle down on command. Some people had trouble getting their dogs engaged in play. Not me! All I had to do was scuffle my feet around a bit, and Shelby would be running around my legs, barking nonstop. The instructor's told me the circling and yapping was the "herding instinct" in her. Herding dogs are bred to be stimulated by movement.
Sometimes her eagerness can get in the way of her figuring something out. For example, I sometimes play a game like hide-and seek with her. I'd have her sit and stay, then go into another room and hide a toy of hers (usually her Kong). Then I'd tell her to find it. She could actually find the Kong faster when she was first learning the game. Now she often gets so excited she'll pace back and forth, sniffing the same areas of the room over and over and whining. I also think I'd have problems teaching her the more "math" tricks. Since she knows one plus one, I've thought of teaching her one plus two, one plus three, etc. But she usually starts barking before I've finished the question. I start to say, "What's o-" and she'll already be going, "RUFF! RUFF!" So I don't know how I could teach her any more tricks like that.