There are many ways to define intelligence. Webster’s Dictionary says that intelligence is the ability to learn or understand, or to deal with new or trying situations.- To reason: the skilled use of reasoning. – The ability to apply knowledge to a given situation or problem.
Therefore your dog’s problem-solving abilities are perhaps one of the best ways to determine how mentally adept they really are. Your dog may not know how to fetch a ball, catch a frisbee, sniff out drugs or open a car door but that desn’t mean your dog isn’t smart. After all they automatically know that you are leaving the house whenever they hears your keys rattle. This shows a kind of intelligence, too.
Intelligence in dogs is measured differently by different people. If you ask 50 people to describe what an intelligent dog is, you will probably get 50 different answers. My dog does several dificult behaviors and my friends say: “Wow, your dog is really smart!” A friend of mine has a dog that can pick up several different toys by name when asked. Maybe your dog has figured out how to open the back door and let itself out to go potty, like one of my neighbor’s dogs has.
Intelligence is not determined by how fast a dog solves a problem either. Like humans, it may take some time to solve a problem at first. Persistence is an important part of problem solving. More intelligent dogs can also be more difficult to train because they tend to question why they need to do some behaviors. Just like some humans do.
There are two different kinds of intelligence: Instinctive and adaptive intelligence. Instinctive intelligence is part of breeding. Dog’s are bred to do different jobs. Certain dogs and breeds have inherent differences in natural ability. Some dogs are bred to track, some to retrieve, others to search for scent and still others are used herd other animals. So IQ tests must take this into consideration.  
Adaptive intelligence is the ability to learn a task or skill based on training or outside input. This includes environmental learning, social learning, language comprehension, and task learning. This is similar to some humans being better at math or being able to learn new skills in order to work at a new job. 
Standard Tests
Here are a few basic tests that you can do with your dog. Use the scoring system to gauge your dog’s intelligence. Don’t try to do all of these tests in one day. It could stress or overwhelmed your dog. Stay calm and don’t correct or yell at your dog during this series of tests. You MUST make these tests fun for your dog. Treat them like games!  And above all, no matter how high or low the scores are, give them lots of love and positive attention afterwards.
There are more tests available based on your dog’s breed that test your dog’s Instinctive intelligence, but these will give you a good base.
Towel test:
Take a large towel or blanket and gently place it over your dog’s head. Time him to see how long it takes him to remove the towel or blanket. If he does it in less than 15 seconds, give him 3 points. If it takes 15-30 seconds, 2 points.  Longer than 30 seconds earns 1 point.
Covered Treat test:
With you dog in a sit, show your dog a treat and let him sniff it. While the dog is watching, cover the treat with the towel. Tell the dog “OK” or encourage your dog to get the treat and start timing. If your dog get the treat in 15 seconds or less give 3 points, 15 to 30 seconds 2 points, 30 to 60 seconds or more 1 point.
Smile test:
With your dog sitting about 10 feet way, (The dog must not have been told to stay or sit.)
Stare intently into your dogs eyes – when your dog makes eye contact, count silently to 3 seconds and then smile broadly. If your dog comes to you with tail waging give him 3 points. If your dog stands or rises but does not move toward you give 2 points. If your dog moves away from you or  pays no attention to you give 1 point
Bucket test:
Place a dog treat or your dog’s favorite toy under one of three buckets placed next to each other on the floor. Let the dog watch which bucket the treat is under. Remove the dog from the area for one minute. Then, let him go back to the buckets to find the treat. If he immediately goes to the correct bucket give him 3 points.  If he takes two attempts, score 2 points.  If your dog looks under the other two buckets first, score 1 point.
Favorite spot:
With your dog out of the room, rearrange the furniture completely. When he re-enters the room, if he goes directly to his favorite spot give him 3 points. If he investigates the room before he finds his spot, give him 2 points. If he decides on a new area completely, score 1 point.
Chair puzzle:
Place a treat under a low platform that is low enough so your dog can only fit his paw under it. If your dog figures how to reach the treat within one minute, score 3 points. If he uses his paws and nose, score 2 points. If your dog gives up, score 1 point.
Go for a walk!
On a day or time you normally don’t walk your dog, quietly pick up your keys and your dog’s leash while he’s watching you. If he gets excited immediately, score 3 points. If you have to walk to the door before he knows it’s time to go out, score 2 points.  If he sits and just looks confused give him 1 point.
Barrier test:
Build a cardboard wall that is 5 feet wide and taller than your dog is when he’s up on two legs.  Build it so that it is free standing.  In the center of the cardboard, cut a 3 inch-wide rectangular slot that runs from about 4 inches from the top to about 4 inches from the bottom. (This is so your dog can see through the wall but cannot physically get through.) Toss a toy or treat to the other side of the wall, or have someone stand on the other side. If your dog walks around the wall within 30 seconds, give him 3 points.  If he goes around the wall in 30 seconds to one minute, give 2 points.  If he gets his head stuck in the slot trying to get through, give 1 point for effort!
Scoring and results
19 points or higher – Brilliant!
15 to 18 points – Well above average
14 to twelve points – Average
8 to 13 points – Below average
1 to 7 points – Not the brightest kibble in the bag, but we still love ’em!
This testing can give you a general idea about your dog’s intelligence. Your dog may not get first place at a dog obediance trial and may lose his favorite ball from time to time. But you must agree that when it comes to making us happy, our favorite pets are all brilliant!