It's not all that surprising to see poodles on a list of intelligent dogs (Stanley Coren ranks them behind only border collies): standard poodles were originally retrievers and working dogs; they are (or were) put to work where initiative, discipline, and the ability to learn are selected for.
Coren ("The Intelligence of Dogs") divides intelligence into instinctive (inbred behavior), adaptive (problem solving), and obedience (following training) components. The problem is that he then relies exclusively on the obedience component.
By any measure, though, border collies and standard poodles are in a class by themselves, especially when it comes to taking the initiative and solving problems -- as well as getting into really big trouble if they aren't given enough to do.
A lot of dogs that score low on these intelligence scales are not stupid but stubborn. Basenjis are an example: they know what they are there to do, and you're not going to tell them otherwise. Shih Tzus, on the other hand, may just be airheads.