Do you have a pet? Does it make you happy? Does it also make you . . . healthy?

Florence Nightingale is the historical hero who founded modern nursing. As long ago as 1860, she said that “a small pet is often an excellent companion for the sick, for long chronic cases especially.” In other words, an animal can help someone who is sick for a long time hang in there.

Science backs up Miss Nightingale. Scientists have learned that heart attack patients who own pets live longer than those who don’t. They discovered that petting a dog could lower blood pressure. Pet contact increases the level of oxytocin—a “happiness chemical”—in the brain. A brain flooded with oxytocin is readier to heal.

But not just any animal is up for a companionship job. What makes a good therapy animal?

Horses. A person using a horse for therapy can benefit in two ways. He or she can bond with the horse emotionally, and increase physical strength through riding. A good therapy horse is quiet, has good manners, and doesn’t mind people walking alongside. A shout or sudden movement doesn’t spook it.

Dogs. A good therapy dog is calm and steady. Even an obedient pup won’t do well at therapy if he’s a ball of energy. Therapy dogs should also tolerate pain well. What if a kid client grabs the dog roughly? A steady therapy animal won’t bite or growl even then.

Birds. Yes, birds can be therapy animals too. And unlike horses, dogs, or cats, some can talk back! A parakeet will chatter away and learn to copy human words. Macaws jabber too, and may even call out to their owners for attention. Cockatiels fill a lonely house with song, and even quiet doves provide a soothing coo.