The ASPCA ads are hard to resist. You know the ones – with video of sad looking dogs and cats waiting for new homes. They are narrated by Sarah McLachlan, or accompanied by Willie Nelson music. They pull at my heartstrings, and make me wonder if it is time to bring home another dog.

Why is it that the plight of animals touches a nerve with so many of us? I went to see the movie “Warhorse” last month, and while the scenes of humans being killed or injured on the World War I battlefields were difficult to watch, it was the abuse of animals during the war that really made me squirm. In a similar way, the local farm animal sanctuary periodically sends out newsletters with stories of some of the animals they rescue. The stories are often horrifying in terms of the neglect and abuse the animals have suffered, but they usually end happily with the animals finding a home for life at the sanctuary.

Animals have been companions to people for thousands of years. Even before we had domesticated dogs and cats, people’s farm animals often slept in the same shelter with them. For many of us, having a companion animal comes naturally. My family’s dog, Alex, was a part of our life for 10 years, and even though he’s been gone for more than two years now, I still miss him.

There’s a large body of research about the benefits that animals can provide for people. The unconditional love that they give us is hugely important given that we are often so critical and judgmental of each other. People who might otherwise be sedentary get more exercise if they have to go out and walk their dogs regularly. Many studies have shown that petting an animal, or even gazing at fish in an aquarium, can lower blood pressure and sometimes heart rate.

Some people even show a decrease in stress hormones when they are interacting with their dogs. But for every stress-reducing benefit of having a pet, there’s also the possibility of stress-inducing effects. Our dog suffered from several chronic conditions in his last few years, and I often experienced a lot of stress related to vets, medication complications, and the cost of care. That’s a big part of what’s holding me back from adopting another dog now.

But we also can learn a lot from animals. Kids who help care for a pet learn responsibility, and how to put the needs of someone else before their own. Alex taught me a lot about how to relax – when he plopped down to sleep, he would often give a deep sigh of contentment, as if to say, “This is the best!” I’d watch him sleep sometimes; he had a peacefulness that I often envied.

Last month, the New York Times ran a piece called, “What We Can Learn from Old Animals” featuring images shot by photographer Isa Leshko. The project of photographing elderly animals was a way to work through her grief after the death of her mother. She said that the experience helped her, “better understand and make peace with aging.” That makes sense to me because when my dog was near the end of his life, he showed incredible patience and forbearance, and I’m grateful for all he taught me.

John Grogan (the author of Marley & Me) has said, “Such short little lives our pets have to spend with us, and they spend most of it waiting for us to come home each day. It is amazing how much love and laughter they bring into our lives and even how much closer we become with each other because of them.”