A dog gives a protective bark, sensing a nearby stranger. A cat slinks by disdainfully, ignoring anyone and everyone. A cow moos in contentment, chewing its cud. At least, that’s what we may think animals feel when they act the way they do. We take our own lived experiences and fill in gaps with our imaginations to better understand and relate to the animals we encounter.

Often, our assumptions are wrong. Take horse play, for example. Many people assume that these muscular, majestic animals are roughhousing just for the fun of it. But in the wild, adult horses rarely play. When we see them play in captivity, it isn’t necessarily a good sign, says Martine Hausberger, an animal scientist at CNRS at the University of Rennes in France.

Hausberger, who raises horses on her farm in Brittany, began studying horse welfare about three decades ago, after observing that people who keep horses often misjudge cues about the animals’ behavior.

Scientists studying animal behavior and animal welfare are making important strides in understanding how the creatures we share our planet with experience the world. “In the last decade or two, people have gotten bolder and more creative in terms of asking what animals’ emotional states are,” explains Georgia Mason, a behavioral biologist and animal welfare scientist at the University of Guelph in Canada. They’re finding thought-provoking answers amid a wide array of animals.

For instance, recent studies hint that picking up a mouse by its tail casts a pall on the animal’s day, and that an unexpected sugar treat may improve a bee’s mood. Crayfish might experience anxiety; ferrets can get bored; and octopuses, and perhaps fish, can experience pain.

Such findings could drive changes in how we treat the animals in our care. For instance, a broad scientific review published in November 2021 by the London School of Economics and Political Science concluded that certain invertebrates such as crabs, lobsters and octopuses should be considered sentient — that is, capable of subjective experiences such as pain and suffering. The conclusions suggest that protection afforded by animal welfare laws should extend to these creatures. One possible outcome: Updates to U.K. animal welfare legislation may make it illegal to boil lobsters alive, requiring swifter, less painful methods to kill the animals.

Yet studying what animals experience is a challenge, says Charlotte Burn, an animal welfare scientist at the Royal Veterinary College in Hatfield, England, and an author of the 2021 review. Researchers can make scientific inferences about how an animal feels based on observable clues from physiology or behavior, she says. But feelings are subjective. “So doing science about this is a bit strange,” Burn says, “because you have to get comfortable with the fact that your key thing is unknowable.”