Some dog breeds
are smarter than others. It is true that stimulation and handling are important in expanding a dog's intelligence, but some breeds are predisposed to intelligence. The pure breeds tend to be dumber than mutts, from my experience. However this is not true in all cases. Larger dogs seem to comprehend anything you try to teach them better than the smaller toy breeds. This is because the mass inbreeding programs practiced centuries ago, in order to turn these dogs into 5 pound decorations, have effected the capacity of these dogs to grasp concepts of every day living. To answer your question about smartest breeds(I assume you mean pure bred dogs); The poodle and labrador are far from the top. The border collie, though fairly smart,
doesn't deserve top spot. You see when people refer to "smart dogs", they usually refer to trainability. Trainability has little to do with intelligence. Think about it. Is it smarter to sit on command, or to ask "why should I sit?"? Border collies and poodles are both quite easy to train. But if you fall through the ice and scream a command they have never heard before, like "HELP" they will stare at you with a dumbfounded look, and probably run a course of commands they know trying to make you happy, while you freeze to death.
True intelligence lies in dogs such as Alaskan malamutes and St. Bernards. Dogs which can assess the situation, and act accordingly(i.e. grab your sleeve, pull you from the water and lead you to shelter). Dogs with the capability to think for themselves are, perhaps not as much of an asset as a trainable dog, in day to day life, but they will be better companions if you don't need a dog for a specific purpose. So if you need a dog to heard sheep, get a border collie. To retrieve game from water, a poodle(full size. toy poodles are useless little s***s) or labrador is a good choice. If you really want a smart dog, go for a dog with a proven track record for independant thought(primarly the medium to large working breeds and especially the primitive breeds). I Don't know if you will read this since the thread is a year old, but I thought I might shed some light on a thread where all I hear is "It all depends on how you train them."(except you emma. you were on the right track. just a little vague). Anyway, everyone have a good day.

Laters