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For more than a decade, in blog posts and scientific papers and public talks, the psychologist Hal Herzog has questioned whether owning pets makes people happier and healthier.

It is a lonely quest, convincing people that puppies and kittens may not actually be terrific for their physical and mental health. “When I talk to people about this,” Herzog recently said, “nobody believes me.” A prominent professor at a major public university once described him as “a super curmudgeon” who is, in effect, “trying to prove that apple pie causes cancer.”

As a teenager in New Jersey in the 1960s, Herzog kept dogs and cats, as well as an iguana, a duck, and a boa constrictor named Boa. Now a professor emeritus at Western Carolina University, he insists he’s not out to smear anyone’s furry friends. In a blog post questioning the so-called pet effect, in 2012, Herzog included a photo of his cat, Tilly. “She makes my life better,” he wrote. “Please Don’t Blame The Messenger!”