Good article.  Couple of highlights for me: 

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"There are a lot of things we can do with dogs -- like obedience classes and training -- that we can't do with people," he said. "Exposure to obedience classes was associated with more positive personality traits across the dog's lifespan. This gives us exciting opportunities to examine why personality changes in all sorts of animals."

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"Older dogs are much harder to train; we found that the 'sweet spot' for teaching a dog obedience is around the age of six, when it outgrows its excitable puppy stage but before its too set in its ways."