Thanks for the great question!

Psychologists are scientists who study emotions. These scientists see emotions as an organized and adaptive response to whatever situation a person finds themselves in. What I mean by this is that particular situations produce different emotional responses, and those responses prepare us to deal with that situation. For example, when someone is scared, their heart rate goes up, preparing them to take action if needed.

The biologist Charles Darwin recognized that humans and animals share many of the same emotions in an 1872 book he wrote called The Expression of the Emotions in Man and Animals. In this book Darwin demonstrated that people from around the world make the same facial expressions when they feel the same emotions. For instance, smiles around the world all mean a person is happy. This is true for people of all ages, too. Darwin also noted that the facial expressions of closely related species like chimpanzees are highly similar to human expressions. From this insight we now know that animals feel emotions that, in some ways, are similar to those of humans, especially highly social mammals like apes and dogs. These animals express their anger, fear, but also happiness and excitement through their expressions and communications. Elephants, in fact, are known to even grieve for the death of relatives.

When talking about the emotions of animals, however, we must be careful not to anthropomorphize, that is, to think about them as though they were human. But animal emotions remind us of our shared evolutionary origins.

Thanks again for the great question.
Best,

Fascinating question! As a paleontologist who studies creatures that lived millions of years ago, I think that I can provide a little insight even though I'm not an expert.

First, it's useful to remember that humans are but one kind of animal (also a kind of mammal, primate, etc.), so it's best not to split the world into humans and "animals." So...humans obviously experience the kinds of emotions you mention, raising the question of what other animals do too.

Humans are unique in being able to talk. How can we tell how other animals are feeling, if they feel at all? Well...in the case of my dog Huxley, it's usually pretty easy. As I go to work in the morning and say "bye bye," he drop his ears and collapses on the floor. I'm pretty sure he's sad. Similarly when I open the door after coming home, he leaps all over the place and runs in circles, pretty clear indications he's happy. I would be amazed if not all mammals have the emotions you describe.

As we move to other animals, however, it gets harder and harder to tell. Birds? Probably, but I'm guessing. Ants? Probably not, but again I'm not sure. Perhaps some of my colleagues in psychology can answer your question more definitively.

I'm quite certain, though, the humans are not the only animals that feel happy or sad.

Yes, many animals at least do feel emotions. There are probably some that do not, but certainly many do. Mammals, birds, other reptiles, and cephalopods (squid and their relatives) are all well-known to have emotions. Most other animals are less intelligent, and it's difficult to determine what, if any, emotions they feel, but since emotions are hardly unique to humans, it is likely that even less intelligent animals can still feel them.

The simple answer is yes, but it really depends on what kind of animal and which emotion you are wondering about. Early on in the history of life, animals evolved the ability to move toward those things that cause pleasure, and move away from those leading to pain. For example, reptiles, such as iguanas, seek out warmth, which triggers physiological responses of pleasure, such as body-temperature and heart-rate increase, which are also what happen to humans during pleasure. Basic emotions, such as fear, anger, sadness, disgust, surprise and happiness are possible to recognize in many animals, because they trigger characteristic automated action programs, such as physiological changes, vocalizations and facial expressions. However, some emotional states may correspond to internal changes in body and brain function that may be too private and subjective to observe.

Scientists can measure hormones and neurotransmitters that are released in the brain during emotional states of animals. For example, just like human brains, other animal (for example rat) brains also release dopamine and opiates while happily playing. The joy that “play” brings is a social emotion, which is a more complex state than the excitement of finding food. Examples of social emotions are grief, guilt, embarrassment, shame, contempt, jealousy, envy, pride, admiration and compassion. These are also accompanied by automated bodily reactions, but also involve more complex conscious reflection that evolved more recently. Two of these may even be exclusively human: admiration, and the kind of compassion that focuses on the mental and social suffering of others. Primates, like the great apes seem to have evolved compassion too, but only the kind toward physical pain of others.

As Darwin first noted, the differences among the emotional lives of many animals are differences in degree rather than in kind.

There’s a lot of debate in the zoology and psychology fields about whether or not animals experience emotions as we do, and bthere’s a lot of evidence that they do!/b There are examples of animals feeling a really wide range of emotions. For example, elephants mourn the death of an individual in their group: video

Yes, animals have feelings. There is a ton of observational evidence to support the claim that animals exhibit some kind of emotions. If you ride horses, you will know that a horse can feel excited, happy, or afraid. If you have a pet you will know that animals can have distinct personality traits such as being curious, friendly, or stubborn. The difficulty is that we simply cannot know what it is like to be an animal other than human, and so we don't know if an animal's feelings are similar to our own experience of emotions. Different animals have different cognitive abilities so it is very difficult to know which animals can have which emotions. Certainly, mammals that have highly developed brains and highly developed societal systems, (such as whales, elephants, dolphins, and apes) experience a range of emotions such as grief, joy, jealousy, affection, loyalty, and more.