What are animals thinking? They feel empathy, grieve, seek joy just like us.

I have lived for eight years now with my dog, Charlie–a bloodhound who’s embarrassingly bad at tracking scents. He greets me with joy every time I return home from grocery shopping, even if it’s just for a quick trip. I can hear his tail go thump-thump-thump on the floor in the next room when I laugh; he echoes my mirth even when he can’t see me. Despite our shared bond, I still find myself sitting next to him on the couch and giving him a hug. I also ask my wife “Do you think that he loves me?” She replies with only slight exasperation. I ask this question so often because it is so charitable. This routine almost feels like a daily ritual in our home. I wonder if Charlie has any thoughts. As he lounges on our front porch, I think deeper about the question: How much do animal minds resemble human minds? Are other species capable of thinking, feeling, and remembering the same way as us?

Humans still consider themselves to be exceptional beings that are fundamentally different from other animals. Scientists have found evidence of intelligence in many species other than humans over the past 50 years. New Caledonian crows snip twigs to fish insect larvae from tree trunks. Octopuses solve puzzles and shield their dens by placing rocks at the entrance. It is not difficult to see that many animals have impressive cognitive abilities. Are they more than simply intelligent automatons whose sole purpose is survival and reproduction?

A growing number of behavioral studies, combined with anecdotal observations in the wild–such as an orca pushing her dead calf around for weeks–are revealing that many species have much more in common with humans than previously thought. Elephants grieve. Dolphins are there for the joy of it. Cuttlefish are unique in their personalities. Ravens respond to other ravens’ emotions. Many primates have strong friendships. In some species, like elephants and orcas the elders share their knowledge with the younger ones. Several others, including rats, are capable of acts of empathy and kindness. (Learn more about the hidden world of whale culture. )

This emerging picture of sentience, of rich inner lives, among surprisingly varied nonhuman species represents something of a Copernican revolution in how we view other beings on our planet. The minds of animals was not a topic worthy scientific inquiry until about three decades ago. Frans de Waal, an Emory University professor and ethologist, recalls that animal emotions were only for romantics. He has spent a lifetime studying primate behavior. De Waal was among the first to advocate for recognition of animal consciousness. He says that scientists started to accept that certain species were sentient a few decades ago but that their experiences were not similar to ours and therefore not significant.

Some behaviorists now believe that the inner processes of many animals are just as complex as humans’, de Waal states. “The difference is that they can express them in language; it’s possible to talk about our feelings.” If this new understanding is widely accepted, it could lead to a complete overhaul of how humans relate and treat other species. De Waal states, “If you recognize emotions and the sentiences of insects in animals, then they become morally pertinent.” They are not the same as rocks. They are sentient beings.” The scientific quest to understand the inner lives and habits of animals is still in its infancy. It is also controversial. Some scientists believe that it is impossible to know the mind of another species. David J. Anderson, a neurobiologist at California Institute of Technology, says that attribution of subjective feelings to an animal through its behavior is not science. It’s just guessing. Anderson studies emotion-linked behaviors of mice, fruit fly, and jellyfish. Researchers who study emotions like empathy and grief in nonhumans need to be careful not to anthropomorphize their subjects.

The best way to find out the truth is to test inferences drawn from animal behavior, according to David Scheel, a marine biologist who studies octopuses at Alaska Pacific University. It is clear that dogs are closely bonded to certain individuals if you look at the ages anecdotally. They are domesticated. Can a fox do that? Is that the same emotional range a wolf has? Is an orca capable of feeling that attachment to its pod members? Can a dolphin make friends with a group or diver of fish? All too often, our intuitions lead us astray. You will get people whose intuition is, That’s fake. Whatever it is, that’s not friendship, and other people who think, Well, that’s just silly. You are denying animals their inner lives.”

If anthropomorphizing is an assault on scientific thinking, I stand guilty of indulging in it. I enjoy watching videos of animals displaying emotions that are similar to ours. A water buffalo working hard to flip a turtle on its back in a zoo. Then, it acknowledges cheers from the onlookers and gives a very self-satisfied look. A panda is seen sledding down a snow-covered hill before trudging up to try again. A monkey at the canal’s edge, peeling a banana before it plunges into the water. These videos are what I show my wife every day, with a silly grin plastered all over my face. I feel happy thinking that the world around me could be vibrating with emotion.

These musings are not scientific, obviously, but what scientists do recognize is that emotions didn’t evolve in humans alone. Emotions are fundamentally internal states that drive animals to act in a certain manner. Although we may not consider hunger and thirst emotions, they are very similar in that they are both internal states that drive an animal to take action. Scheel calls them primordial emotions. Scheel describes them as primordial emotions. He explains that it is becoming imperative.

Just like the invisible “imperative,” primordial emotions such as fear prompt specific actions. Although emotions like love or sorrow may seem more profound than others, they are qualitatively not different. “All of our scientific and philosophical work right now,” Scheel says, “is pointing to the idea that any emotion you care to name, however lofty and high and ethereal, is built up from these primordial emotions.”

If that’s the case, it’s not hard to appreciate that a wide variety of species–from fleas to chimpanzees–have emotions, primal in some and advanced in others.

The ravens regarded me warily, hopping away when I stepped too close to the wire mesh that separated us. The cage was lit by sunlight, which reflected off the feathers’ silken, jet black sheen. Thomas Bugnyar, an Austrian behavioral and cognitive biologist, had made a remarkable observation about their behavior. After about 10 minutes, the birds seemed to relax. One shuffled cautiously over to get a better view of me, turning its face and sizing up alternately with its left and right eyes.

Corvids–the family that includes ravens–are known for their intelligence. Scientists have demonstrated that they can use tools to solve problems and plan for the future. I was able to see one of them hiding a treat during my visit. It placed a small stone over the treat and then walked off. It returned minutes later, apparently unsatisfied, to grab the treat in its beak and hop over to another location to place it in the gravel.

Ravens have impressive cognitive abilities, but they also display behaviors that suggest another facet to their intelligence: empathy. Bugnyar observed that when two ravens fought, a witness seemed to console the loser. This was years ago while Bugnyar was studying raven behavior for his doctorate. When I visited him in his office, he described a typical scene. He was observing a taxidermied raven perched on a branch as a wedding gift.

“Two people engage in a fight. The victim is chased for a few minutes, then he flies into a corner and sits there shaking.” he said to me. “And the other ravens, very aroused, are flying around calling and then one of them flies towards the victim, not directly but near.” The raven makes friendly calls, moving closer until it is within touching distance. The consoler will continue to be used even if the victim moves away. “After a couple of minutes, it ends up grooming the other one.”

Bugnyar documented 152 such encounters. Orlaith Fraser, a colleague, and Bugnyar discovered that ravens supporting victims were often well-informed. Researchers had previously seen consolation behavior in bonobos and chimpanzees; Bugnyar was the first to discover it in birds.

Scientists have been able to investigate the phenomenon in greater detail by conducting experiments with rats. Inbal Ben-Ami Bartal of Tel Aviv University designed one that contained a rat inside a transparent plastic tube filled with holes. The tube’s door can be opened from outside. Researchers placed the tube in a cage that allowed another rat to move freely. The tube is filled with rat urine and the rat tries to escape by squirming. The other rat can see its distress and begins to circle the tube, biting it, and trying to get underneath it. After several sessions, the rat finally learns how to open the door. Once it has mastered this trick, the freerat is quick to release the trapped rat.

This helpful behavior is dependent on whether the free rat feels kinship with the confined rat. A trapped rat will be helped if it is raised with other rats of the same type. If the trapped rat is of another genetic type, the freed rat will not be disturbed by its plight and won’t let it go. If a rat of one type is raised with rats from another type, it will help only those rats, and ignore the distress of others. Ben-Ami Bartal explains to me that it is not about biological similarities. It’s about loving the people you share your life with. It’s about having your family and knowing that that’s your family.”

A necessary feature of emotional intelligence–including the capacity to respond to a fellow creature’s distress–is the ability to read the emotional state of others. On a windy morning I stood at the edge of a muddy field to watch Leanne Proops, a psychologist from the University of Portsmouth, demonstrate how horses can read emotions.

It is obvious that Proops, a researcher from the University of Portsmouth, is passionate about her subjects. Every time I saw a horse, my smile would widen and her eyes soften. She would always reply, “Very sweet!” We leaned against a fence and each board was printed with a large photograph of the horse’s head taken from the front. One showed the horse’s ears perked up, his nose and mouth were open, and the eyes looked calm. The horse in the second had a threatening expression. His ears were pulled back, his jaws were clenched, and his nostrils flared.

Our first study subject was a reddish-brown horse that a graduate student led out of a barn. After walking it around for a few minutes, she led it to the faces of the horses and then took off the lead rope. We wanted to see how the horse would react to the photographs. Is it more interested in the happy horse’s face?

Proops held her breath. The horse looked briefly at the images before moving to a corner of a field, waving its tail and gazing out at the grassy meadow below. Proops had warned me that this could happen. Animal scientists can be baffled by whimsical subjects.

The student brought out a gray-white horse with a soft and shiny mane. This one was more cooperative. After a few minutes of contemplating the photos, it moved up to the happy face and nuzzled that photo.

Proops and her colleagues put 48 horses through a test like the one I watched. Some were given the option of seeing a happy or angry horse. Others were shown a neutral or angry face. Horses had no preference for the neutral or happy faces when presented with the option. The researchers were surprised to find that horses can recognize the expressions of horses they have never met.

Proops also conducted another study in which a horse was shown a photo of a human face, either smiling or angry. The photograph was shown in morning. The photo was shown in the afternoon. The horse displayed signs of stress if the person in the photo was angry. The horse looked at the person with its left eye more than its right, a sign that horses exhibit when they perceive a threat. It rubbed its ears and tightened its lips. The horse was more likely to react positively or neutrally to photos of happy faces or people who were different from it. The findings from this study, also tested on 48 horses, suggest that horses might have a nuanced ability to read and respond to emotional states not only in horses but in humans too. This behavior shows advanced memory and recognition skills. They had to be able to transfer a photo to a person. She said that they had to be able to recall a specific person and the emotion.

“That’s amazing,” I remarked.

“Yeah, yeah,” she said, beaming. “It is.”

Occasionally, Charlie moans and twitches in his sleep. I can picture a nightmare where he would be scared, like when a truck comes down on him. He is very agitated when he sees loud vehicles. I can only soothe him by stroking his head, but I wonder what he was dreaming. I’m not the only one who wishes I could see inside an animal’s mind.

Christina Hunger, a Chicago-based speech-language pathologist, had the same desire when she brought home a puppy four year ago. Hunger uses a communication device, a board with buttons that produces prerecorded words, to help children with language delays. Stella, a blue heeler-Catahoula mix, was curious if she could be taught to press buttons for words like “water”, “play,” or “outside”. Stella was quick to learn and began using the buttons to communicate her desires after about a month. Stella ran into Hunger’s room to water her houseplants one day and pressed the button for water. She returned to Hunger to continue watching. Her water dish was full. She didn’t drink any water. Hunger says she was simply using the word in an entirely new way. Stella seemed to be merely pointing out what she had observed.

Excited by the prospect of learning more about Stella’s inner life, Hunger introduced her to a few dozen more words, such as “help,” “bye,” “no,” and “love you.” One evening, Stella had something important to say. “She walked over the ‘eat’ button, said, “Eat,” then walked across the apartment to her no’ button, and said, “No, ” Hunger recalls. “So she combined those two words to let us know she hadn’t eaten dinner.”

Hunger then put the buttons in one place–48 in all–to make it easier for Stella to use multiple words, which led to an explosion in communication. Hunger says that she started to combine words every day, multiple times per day, in order to create new messages that were consistent with the environment. In How Stella Learned To Talk, she shares her story.

One day this past spring, Hunger was on the phone when Stella tried to get her attention. Stella tried to get her attention by pressing the buttons for “look”, “come”, and “play”. Hunger was busy so Stella kept trying different messages, including “Want.” Play. Outside.” Finally, she was frustrated and pressed “love” followed by “no.” She was utterly shocked. “I didn’t think I would create a ‘love me’ button that would allow her to tell me, “Love you.” She says, “No, not when she’s mad about me.” “But it’s just amazing to see all the thoughts that are going on in her head.”

Stella isn’t the only dog to have opened a window to her inner life in this way. Other dog owners have been using communication devices with their pets in recent years. The trend prompted Federico Rossano, a cognitive scientist at the University of California, San Diego’s Comparative Cognition Lab, to launch a study in which almost 3,000 dog and cat owners have sent reports of their pets using buttons to express words.

Rossano says he’s seen numerous examples of dogs inquiring about a family member because the person has been absent. They combine the words “park” and the name of the dog to express their desire for play with specific dogs. He says, “It’s amazing how many times we see instances where there are two animals in a household and one asks for help from the other one.” One video he shared with him shows Bastian, a terrier, watching Hallie, an elderly cat, sit down as she has trouble moving. He runs over to the buttons, presses “concerned” or “walk,” but I haven’t signed Charlie up yet. No.”

Diana Reiss, Whose eyes light up when the subject is marine mammals, was filming bottlenose dolphins in an aquarium in the 1980s when she made a startling discovery. One of the dolphins she saw was swimming to the bottom, exhaling a ring from its blowhole. The silvery ring was rising towards the surface when the dolphin exhaled a second, smaller ring. It merged with the first to create a larger ring. The dolphin then swam through the ring. Reiss, a Hunter College cognitive psychologist, couldn’t believe her eyes. She says, “This was the first instance that you’ve ever seen an animal create its own object or play itself.”

It wasn’t a one-off. Reiss and others have seen dolphins play with each other in aquariums. Dolphins chase one another in the wild. They are just one species of the many species that engage in play, along with dogs and cats. Baboons have been observed pulling the tails of cows to taunt them. Richard Byrne, an African researcher on the evolution of cognition, observed that young elephants would pursue non-threatening animals like wildebeests or egrets while studying elephants in Africa. Gordon M. Burghardt (an ethologist at The University of Tennessee, Knoxville) said that scientists have also found evidence of playful behaviors in fishes and reptiles. He has seen mossy frog tadpoles from Vietnam riding air bubbles from the bottom of a tank all their way to the top.

Play is energy-intensive and can even cause injury, but it serves an important purpose. Why is it that animals play? Researchers believe play evolved because it strengthens the bonds between members of different social groups. It helps animals learn skills like running and jumping that will increase their survival chances. This is the reason play evolved. But what is the impulse that drives an animal to engage in play? Vincent Janik, a biologist from the University of St. Andrews, Scotland, believes that joy is the answer. “Why does an animal do what it does?” He says, “Because it wants to.” It seems that play enriches the inner lives of animals and gives them pleasure.

How rich are the inner lives of animals that live in social groups, as we do? Sarah Brosnan, an anthropologist at Georgia State University, conducts experiments to see inside the minds of capuchin monkeys. She took me on an excursion around the research facility that houses six groups capuchins. Each group has an outdoor wire mesh enclosure where the monkeys can hang out for most the day, whether they are eating, grooming, or playing. It was mid-afternoon, and the staff had just finished distributing food.

Grapes are the favorite food of the capuchins. Brosnan used this knowledge to create an experiment to test their emotional lives. She placed two capuchins side-by-side in compartments separated by wire mesh and played a game. The monkeys quickly learned the rules of the game and had to give Brosnan a token, a small object like a piece or wood, to receive a reward. Brosnan would sometimes give both capuchins a piece each of cucumber. The animals loved it as much as children like oatmeal. Sometimes she gave one capuchin a slice of cucumber and the other a grape. In a third arrangement, there were only one capuchin. Brosnan gave the one monkey cucumbers, but she also allowed her to drop a grape in the empty compartment.

Both monkeys ate the cucumber pieces without complaint. The one monkey who kept getting a grape became visibly upset when the other monkey kept getting cucumber pieces. Brosnan was thrown the cucumber by it. It was clearly unable to handle the unfairness or inequity. The monkey that was only one in a test, saw grapes accumulate in an adjacent compartment. At first, the monkey refused to eat the cucumber, but it eventually started to eat it again. Brosnan states that they don’t seem care as much about the contrast as they do the inequity. The study suggests that humans have an expectation of fairness and a sense of grief when it isn’t met.

Some primates seem to be intelligent enough to have a sense for humor. Researchers agree that chimps and other great apes laugh, mostly when they are playing. They have also been seen laughing in different situations. De Waal tells of a colleague who donned a panther mask to emerge from the bushes and across a moat created by chimpanzees. De Waal says that the chimps became very angry and threw many things at him. The researcher, who was well-known to the chimps, removed the mask and came out. “And some of the chimps–the older chimps–they laughed at this.”

I learned of another example from Marina Davila-Ross, a psychologist at the University of Portsmouth, who showed me a video of a young chimpanzee named Pia that she had filmed at an animal park in Germany. Davila-Ross captured the chimp pulling at her father’s hair in an apparent attempt to initiate play. Pia laid down on the grass when he didn’t reply.

Shortly after, without any triggering event, Pia’s face opened into a wide smile. She then burst into exuberant laughter and threw her head back, folding her arms over her eyes like a child watching a funny cartoon.

According to Davila-Ross, Pia might have been laughing at her father’s playful moment. Although this can’t be proven, it is possible to infer that Pia was having a spontaneous moment of laughter. This suggests that memory and emotion interact in a way that could suggest complexities in her inner world. I was instantly able to smile when I saw the video. I made a mental note of it and promised my wife.