Horowitz, who runs the Dog Cognition Lab at Barnard College, is the author of The Year of the Puppy: How Dogs Become Themselves Puppies aren’t born barking, just as children aren’t born chattering.

“Why do dogs sometimes bark a lot? I have a Yorkie!” commented a young patron from the Grayslake Area Public Library. The dog days are coming soon — the summer swelter that ancient Romans believed ...