I know from seeing my own dogs and those of friends that different dogs have different degrees of ‘smartness’. It’s not a simple linear scale though, but includes several axes:

Stanley Coren, PhD, of the University of British Columbia …, author of more than a half-dozen popular books on dogs and dog behavior, has reviewed numerous studies to conclude that dogs have the ability to solve complex problems and are more like humans and other higher primates than previously thought.

…According to several behavioral measures, Coren says dogs’ mental abilities are close to a human child age 2 to 2.5 years.

The intelligence of various types of dogs does differ and the dog’s breed determines some of these differences, Coren says. “There are three types of dog intelligence: instinctive (what the dog is bred to do), adaptive (how well the dog learns from its environment to solve problems) and working and obedience (the equivalent of ‘school learning’).”

[Via : Dogs' Intelligence On Par With Two-year-old Human, Canine Researcher Says.]