SAN FRANCISCO, Calif. (KRON) — Dogs and cats really do have dreams and nightmares, according to philosopher David Pena-Guzman of San Francisco State University.

Guzman’s new book, “When Animals Dream: The Hidden World of Animal Consciousness,” looks closely at the science of animal dreams. He concluded that our furry friends have a deeper level of consciousness and range of emotions than we realize.

“A lot of people think that dogs and cats … can definitely feel emotions for which there is a very clear evolutionary function. Like fear, it helps you escape from predators. But then there are other, more complicated, emotions that sometimes we’re not sure if animals really have them. The book sheds light on some of those emotions,” Guzman said.

Guzman combed through thousands of sleep studies and found evidence that, like dogs and cats, many species in the animal kingdom dream, too.

“We do have enough evidence to believe that other species have these nightly experiences of a fantastical, almost phantasmagoric world,” Guzman explained on a recent podcast, “Big Brains.”

Guzman noted that the human mind is only one of the many minds that evolved through evolution.

“I think it’s deeply problematic that we tend to think about mind by beginning from the human case, and then looking to see which animals fit into our framework of the human mind,” he said.

One study that peaked Guzman’s interest was a sleep study conducted on zebra fish.

“At some point, when they’re asleep, it’s almost as if there is a neuronal revolution that erupts in the brain, and you start seeing the brain lighting up like a Christmas tree and lighting up in patterns that are comparable to the way in which the brain lights up in you and I. It really extends the possibility of dreaming to species as different from us as a tiny, tiny little fish,” Guzman said.

Another study found that elephants experience terrifying nightmares, especially if the elephant experienced real-life trauma.

“When young elephants, in particular, experience a deeply traumatic effect such as witnessing human poachers murder one of their family members and cut out the tusks, those young animals remember that scene. It just gets burned into their memory. And later when they are asleep, because they’ve been traumatized, they begin replaying that over and over again,” he said.

Animals can also have positive dreams that inspire feelings of aspiration and hope, he added. “Dreams are fundamentally emotional to some degree,” he said.

Guzman explained dreaming as essentially the mind’s self-centered manifestation of life experiences.

In his book, “what I try to do is paint a picture of the emotional depths of other animals … all the complex, deep, revealing, emotional states that they can experience and how sometimes, those come out in various kinds of dreams,” Guzman said.