animals knows they have moods and sometimes the moods manifest in strategically placed droppings throughout your house. But can our pets actually lose their mind? Tonight the author of a provocative... See More
animals knows they have moods and sometimes the moods manifest in strategically placed droppings throughout your house. But can our pets actually lose their mind? Tonight the author of a provocative new book and the depressed goat who she says proves her thesis. Most of us probe baby don't think of goats as having particularly rich interior lives. This goat, Mr. G, is apparently genuinely depressed. A few days before this video was shot he had been rescued from the home of an elderly woman near Los Angeles who was hoarding animals. For a decade Mr. G had lived alongside a female donkey named jellybean with little food and no shelter. It was just really neglect. They lived in a relatively small paddock. They just weren't getting the care that they needed. But when the animals were rescued they were taken to separate shelters which is what sent Mr. G into this deep funk laying in the corner of his stall, refusing to go outside, or eat, for six days. He went off food. In fact he wouldn't get out of his barn. He just sat there and, just, just seemed depressed. In a moment the extraordinary development that makes Mr. G perk up for the first time. But first, kid this. Humans. And other animals can laws their minds. And, ways that are, really similar. A historian of science who has written a book, animal madness, are gaugues humans and animals are similar when it comes to their feelings. And like us, animals can lose their mind. Dr. Brakeman's journey began at home with this guy, her dog, oliver, who suffered from terrible anxiety. Ate zip-lock bags, contents if there weren't food in them. Snapped at flies he couldn't see. Imaginary flies? Yes, hallucinated a little at night. Distressing? Overwhelming. In her quest to find relief she entered into the world of animal slings who diagnosed them with O.C.D. To anxiety and prescribed anti-depressants for animals that chase their own shadows, pee all over the place or bite people. Better to have this product in the background it decreases depression. When we diagnose animals with the same sorts of mental illnesses that we have, are we taking a lep here? How do we really know what is going on with the animals. They can't talk to us. We don't really know what is going on with the animals. We diagnose people without asking them questions verbally all the time. Children can get diagnosed with psychiatric disorders without indepth interviews. You can die agnesagnose a person even when they won't talk about their symptoms. We have an inborn bias recognizing these in other animals. In her research brakeman learned it is not only house pets taking antidepressants. Bobby. There he is. This is bobby. A chimp, rescued from a lab where he had been taken from his mom at birth. And made into a research subject. He was so traumatized by that experience, that he started to do what humans in distress some times do. He hurt himself. Biting into his arm causing serious wounds. It was beyond heartbreaking. Any one who saw bobby didn't have to be especially trained to know he was in severe distress. With the help of psychiatric meds he is now a new chimp. This make is my heart sing. What the doctor found in her research for her book is aside from med. You know you are a happy chimp when you start holding on to your feet. A huge factor in psychological recovery is love. Even if it know it from your own species. Do you love that bobby? Is this okay? I have seen this in my own travels for "Nightline." Hi. How are you doing? What's going on? Go get thecarrot? From babies given surrogate mother after their biological moms were killed by poachers. The food looks pretty good. To this baby elephant, found wound add lenin the fed and alone, in the forest in cam bbodia. And the elephant has benefited not only from human companionship but from an older elephant named lucky. They look to play soccer, spin their handlers around, and even dance the macarana. For a price of course. Laurel says if we can learn to recognize that animals of all sorts, from elephants, to dogs, to pigeons, deer and chickens have true emotional range, it will change our attitudes about so much, from zoos to what we eat. This work should influence, I believe, how we think about -- the animals that are -- that are put in front of us to entertain us. And -- it also, ideally would change our food system. There are millions of animals in the United States with, with stereotypic or what look a lot like OCD behaviors. Which brings us back to Mr. G, the depressed goat, who misses his long-time donkey companion, jellybean. One of the volunteers at the shelter offered to drive 14 hours round trip to pick up jellybean. The moment Mr. G hears the donkey being unloaded he lifts up his head. As soon as he could smell jellybean. His nose started twitching. He perked up. Then when he heard him and saw him. First, little Mr. G couldn't believe his eyes. And he just got up and became almost instantaneously a different animal. He started getting up, running. Want to jellybean. And put nez to nose. Awe and put nose to nose. And there it is a little kiss. And 20 minutes later, Mr. G eats for the first time in six days. An interspecies love affair that should give pause to anyone who doubts the emotional complexity of the animals with whom we share this world. Dr. Laurel brakeman's new book, "Animal madness" is a available now.
This transcript has been automatically generated and may not be 100% accurate.