The cleverest dog is the one that lives wild,well away from human interferance.
Paul

I'd say my beardie is too clever for her own good  She has a need to understand everything happening around her - and she seems to understand a whole lot Problem is that if there is something weird happening and I can't show her what it is all about she gets easily stressed out  

She is phenomenal when learning new things, she really seems to think for herself!

All mine are clever in there own ways mainly how to manipulate me into getting what they want -Those puppy eyes!! Lucy is problem solving she must have escaped about 50 times in the last few months im still not sure exactly how she does it! Jake can get anything even if you put it out of his reach. You put something as far back on the kitchen side as possible (he isnt that tall) then you turn around for one second and he's got it! And then theres bonnie she's 10 weeks old and can consume 3 times her body weight and produce more mess than the other two and my whole family!

American Bulldogs are very intelligent, almost to the point of being human, never underestemate the intelligence of an AB, or you WILL BE outsmarted

I know this is a late entry, but I have some insight.

None of mine are particularly brilliant. We call them our Unthink Tank.

A lot depends on how the dog has been trained as to how much it thinks for itself.

Rescue and older dogs can easily be trained. What you often do find is that those who acquire older dogs don't train them anything other than the basics. Let's face it, a lot of people get dogs to be companians and aren't interested in training on for sport or obedience. It's not that the dogs aren't capable of doing more, just that both the owner and the dog are content at not doing.

Hiya
Well border collies are said to be the most intelligent, but Cas is really stupid.  She does as she's told and has really good manners, waits till is asked in etc.  But when it comes to working things out or finding a certain toy she's hopeless.  She doesn't know half the things Diz does, if we say a walkie, she hasn't a clue just thinks it's time to run round a lot, does the same for tea time, or anything that Diz responds too.  Some of the things she does are soo daft I wonder wether she has a brain lolol.  Had her at 6 months

Now Dizzy GSD X rough collie is the most intelligent dog i have ever known and people have said the same to me.  She understands virtually everything you say, picks up on feelings can be taught anything within minutes.  She figures things out really quickly.  She really is one clever cookie!  Knows all her toys by name and we must have about 30, then if there's a new toy and we say a word she doesn't recognise with fetch... she knows it's the new one.  Also with people if there's a new person in the house we could say go and find so and so and she knows that it is this new person.  Sometimes she amazes me, I sometimes wonder if she's human in disguise as a dog.  Had her at 6 months.

Ember surprised me, not ever having been around shelties I didn't know what to expect, but she is too very intelligent, like Dizzy - but not as much.  Much more intelligent than the collie.  She knows so many things already and she is 6 months, I am really surprised.  & was house trained at 10 weeks asking to go out.

I walk a border terrier for a friend and he is worse than the collie, he's food motivated and everything but it takes him soo long to learn things.

Gina