Here's a listing of dog IQs by breed. Dogs have undergone artificial selection, so those selected for intelligence (Border Collie) tend to be very smart, while those selected only for appearance tend not to be so smart. It depends on what was being selected for. A bloodhound typically has a low dog IQ (doesn't respond well to commands) but has undergone intense selection for smelling ability, so a bloodhound compensates for lack of command response with a keen sense of smell.
Many have argued that mutts tend to be around average intelligence, depending on their ancestry. A mutt of high IQ ancestry (for example, a Border Collie, German Shepherd & Golden Retriever mix) will be smart, but a mutt of low IQ ancestry (for example, a Chow Chow, Basenji & Pekingese mix) will tend to be dumb.
A veterinarian reader tells me that most mutts today in urban areas are at least part pit bull terrier. Given that pit bulls have low dog IQs, this would mean that the average IQ of mutts would be on the lower end of the spectrum. (N.B. that pit bulls also have undergone recent heavy artificial selection for aggression, since they're often raised to fight.)
It should also be noted that pariah dogs (mutts in the wild that have reverted back to wolf-like characteristics) tend to have low average dog IQs, as by dog IQ one means a dog's responsiveness to human commands. Mutts, left alone for multiple generations, will develop pariah traits and eventually will lose traits of domestication, which means their dog IQ will drop.
It should be noted, however, that what we think of as dog intelligence (response to commands) is not all that dog breeds underwent artificial selection for. For instance, breeds were selected for guarding, hunting, smelling, herding, appearance, etc., and each breed seems to have its own special abilities or appearance. Breeds are important. If dog breeds were to disappear and be transformed into a large class of mutts, we would lose the richness of canine biodiversity.
From
The Intelligence of Dogs, by S. Coren
Ranks 1 to 10
Brightest Dogs
Understanding of New Commands: Less than 5 repetitions.
Obey First Command: 95% of the time or better.
Rank Breed
1 Border Collie
2 Poodle
3 German Shepherd
4 Golden Retriever
5 Doberman Pinscher
6 Shetland Sheepdog
7 Labrador Retriever
8 Papillon
9 Rottweiler
10 Australian Cattle Dog
Ranks 11 to 26
Excellent Working Dogs
Understanding of New Commands: 5 to 15 repetitions.
Obey First Command: 85% of the time or better.
Rank Breed
11 Welsh Corgi (Pembroke)
12 Miniature Schnauzer
13 English Springer Spaniel
14 Belgian Tervuren
15 Schipperke
Belgian Sheepdog
16 Collie
Keeshond
17 German Shorthaired Pointer
18 Flat-Coated Retriever
English Cocker Spaniel
Standard Schnauzer
19 Brittany
20 Cocker Spaniel
21 Weimaraner
22 Belgian Malinois
Bernese Mountain Dog
23 Pomeranian
24 Irish Water Spaniel
25 Vizsla
26 Cardigan Welsh Corgi
Ranks 27 to 39
Above Average Working Dogs
Understanding of New Commands: 15 to 25 repetitions.
Obey First Command: 70% of the time or better
Rank Breed
27 Chesapeake Bay Retriever
Puli
Yorkshire Terrier
28 Giant Schnauzer
29 Airedale Terrier
Bouvier Des Flandres
30 Border Terrier
Briard
31 Welsh Springer Spaniel
32 Manchester Terrier
33 Samoyed
34 Field Spaniel
Newfoundland
Australian Terrier
American Staffordshire Terrier
Gordon Setter
Bearded Collie
35 Cairn Terrier
Kerry Blue Terrier
Irish Setter
36 Norwegian Elkhound
37 Affenpincher
Silky Terrier
Miniature Pinscher
English Setter
Pharaoh Hound
Clumber Spaniel
38 Norwich Terrier
39 Dalmatian
Ranks 40 to 54
Average Working/Obedience Intelligence
Understanding of New Commands: 25 to 40 repetitions.
Obey First Command: 50% of the time or better.
Rank Breed
40 Soft-Coated Wheaten Terrier
Bedlington Terrier
Fox Terrier (Smooth)
41 Curly-Coated Retriever
Irish Wolfhound
42 Kuvasz
Australian Shepherd
43 Saluki
Finnish Spitz
Pointer
44 Cavalier King Charles Spaniel
German Wirehaired Pointer
Black & Tan Coonhound
American Water Spaniel
45 Siberian Husky
Bichon Frise
English Toy Spaniel
46 Tibetan Spaniel
Foxhound (English)
Otterhound
Foxhound (American)
Greyhound
Wirehaired Pointing Griffon
47 West Highland White Terrier
Scottish Deerhound
48 Boxer
Great Dane
49 Dachshund
Stafforshire Bull Terrier
50 Alaskan Malamute
51 Whippet
Chinese Shar-pei
Fox Terrier (Wire)
52 Rhodesian Ridgeback
53 Ibizan Hound
Welsh Terrier
Irish Terrier
54 Boston Terrier
Akita
Ranks 55 to 69
Fair Working/Obedience Intelligence
Understanding of New Commands: 40 to 80 repetitions.
Obey First Command: 30% of the time or better.
Rank Breed
55 Skye Terrier
56 Norfolk Terrier
Sealyham Terrier
57 Pug
58 French Bulldog
59 Brussels Griffon
Maltese
60 Italian Greyhound
61 Chinese Crested
62 Dandie Dinmont Terrier
Petit Basset Griffon Vendeen
Tibetan Terrier
Japanese Chin
Lakeland Terrier
63 Old English Sheepdog
64 Great Pyrenees
65 Scottish Terrier
Saint Bernard
66 Bull Terrier
67 Chihuahua
68 Lhasa Apso
69 Bullmastiff
Ranks 70 to 79
Lowest Degree of Working/Obedience Intelligence
Understanding of New Commands: 80 to 100 repetitions or more.
Obey First Command: 25% of the time or worse.
Rank Breed
70 Shih Tzu
71 Basset Hound
72 Mastiff
Beagle
73 Pekingese
74 Bloodhound
75 Borzoi
76 Chow Chow
77 Bulldog
78 Basenji
79 Afghan Hound
Further reading:
Eccles & Mount: "
Cross-breed Dogs Have More Health Problems than Purebred Dogs" (For "
Pariah Dogs," see entry
here.)
Clark: "
Benefits of Hybrid Vigor Overstated"