The kitten loitering outside my local firehouse was still there two hours later, yowling with hunger, when the community council meeting I was attending broke up. “Will you take him home?” asked my neighbor. “My friend Steve wants to adopt a cat, so it would just be for one night.” Of course, I would. But the next day I learned Steve wanted a tabby, and this kitten had a coat as soft as a rabbit's but no stripes. Your loss, Steve. Bunny Boy, now 12 years old and still with me, is my favorite cat ever. That's saying a lot, considering how many pets have shared my home over the years.

At the moment, my husband and I have three cats and two dogs, and I consider myself a cat person and a dog person. There are no hard-and-fast rules, though, about what makes someone a typical owner of either species, as “What Your Pet Reveals about You” explains. In fact, cats and dogs often come into our lives in unexpected ways. They also come in all shapes and shades—a reflection of how their evolution has been affected by human contact, a process described in “From Wolf to Dog” and “The Taming of the Cat”.

When I was a college student majoring in biology more than 30 years ago, ascribing human emotions and motives to animals—anthropomorphism—was frowned on. Today, though, many scientists feel comfortable saying what we pet owners have known all along: that animals feel things. Even rats have empathy for their cage mates, and creatures of many species apparently grieve over the loss of relatives or close companions—as we learn in “Do Animals Feel Empathy?” and “When Animals Mourn”. Yet recent research highlighted in “The World According to Dogs” also shows that pet owners often misinterpret their charges' feelings.

Pets fill our own emotional need to nurture other living things, making us healthier and happier, according to “Pets: Why Do We Have Them?”. Canine companions may even help in the effort to cure cancer, as described in “Cancer Clues from Pet Dogs”. Indoor cats, meanwhile, might not deserve the bad rap they're getting for spreading a brain-altering parasite to humans—a surprise reported in “Played by a Parasite”.

More than half of American households have a pet—usually more than one and often considered members of the family. They bring us joy, occasional sadness (if only because their lives are measured in dog years) and now an unending source of viral videos. Read on to learn why dogs and cats behave the way they do and what makes the human-pet bond so strong.