An answer to the Explainer's 2008 Question of the Year.

Of course, you'll get a different Judas breed for every definition of disloyal and for every method used to assess the dogs. Animal behaviorists Lynette and Benjamin Hart conducted a large-scale survey of small-animal veterinarians and created a table of breed rankings for 10 personality traits. In their system, a "disloyal" dog might be construed as one that ranks high for "aggression towards owner" (e.g., chows, Rottweilers, and Akitas) and low for "territorial defense" (e.g., whippets, golden retrievers, and basset hounds). Once again, since there's no definition or measure of loyalty, there's no accepted answer to the question.

Bonus Explainer: How do you measure a dog's personality? Give the owner a questionnaire, or test the dog directly. There are many standardized instruments for assessing canine temperament; click here (PDF) for a review of the literature. Kenth Svartberg uses something called the "Dog Mentality Assessment," used by breeders with the Swedish Working Dog Association. Here the dog must endure 10 trials as it walks down a wooded path. These include the sound of a gunshot, the sound of a metal chain being dragged across a piece of corrugated metal, and the sudden appearance of a humanlike dummy. (The dummy is pulled off the ground with ropes that are slung over tree branches.) In the most peculiar segment, the dog is rated on its "reaction to two slowly approaching persons covered in white sheets ('ghosts'). … Over the head the functionaries have white plastic buckets with holes for the eyes."

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Explainer thanks Sam Gosling, Benjamin Hart of the University of California-Davis, Diane Mollaghan,and Lisa Peterson of the American Kennel Club.

Previous Questions of the Year:

2007: Why don't we drop medical waste and nuclear waste into active volcanoes, the "ultimate high-temperature incinerators"?

2006: Can a bar of soap get dirty, or is it self-cleaning because it's soap?