A free rat will open the door of a trap. It lets out a rat from its own cage that is stuck inside. After some days of trying, rats opened the trap door with their heads. They did it fast. The researchers did not train the rats to free their cagemates. A rat was as likely to free its trapped cagemate first as to open a container of chocolate.

A free rat acted more upset when its cagemate was trapped. It was as if it picked up the cagemate's distress. Empathy is sensing and sharing what another person is feeling. In a test, free rats shared chocolate chips with a freed cagemate about half of the time. Researchers think that helping a cagemate may itself be rewarding for a rat. Doing something kind for another person can make you feel happier.

In one task, an adult hung clothes on a line. He dropped a clothes peg that he could not reach. Toddlers who were 18 months old helped a grown-up they had never met. They rarely helped in control conditions where the grown-up did not need help. Young chimpanzees helped a person who was reaching for something. They helped in easy tasks but not in the harder ones. Nobody asked or rewarded the toddlers and chimpanzees for helping.

Vampire bats form strong bonds with their colony mates. Some unrelated bats have traveled together for more than ten years. A vampire bat can share some of its blood meal with another bat in its colony. A bat that misses a few nights of feeding in a row can starve. A bat that found no food can beg another bat for blood. A small amount lets it live and hunt another day. Among vampire bats, grooming is mostly associated with food sharing. In some pairs, grooming eventually gave way to it.

Asian elephants comfort other elephants that are upset. They use touch and sounds. An elephant may put its trunk in another elephant's mouth to calm it. A researcher compared this gesture to a handshake or hug. As of November 2026, a 2014 study gave the first scientific evidence that elephants console one another. In a study, pet dogs went up to a person who was crying. Dogs in a study went to a crying stranger, not only to their owner.

A psychologist's study found that doing kind acts raised people's well-being. In one experiment, one person's generosity spread to three people and then to nine. In experiments, generous behavior spread through a group. So did stingy behavior. In a cooperation experiment, a small number of generous people changed how other people in the group behaved.

Words to know

• empathy: sharing feelings
• distress: upset feeling
• toddlers: very young kids
• colony: bat group
• grooming: cleaning fur