Imagine that your friend is cutting the cake to share with all the guests at the birthday party. The first three guests are handed large pieces of cake, while you are handed a teeny-tiny one. How would you feel? Is this fair? Most of us have a clear sense of what is fair and what is not, but where does this come from? Scientists try to study fairness in primate species (灵长类物种) to understand how fairness came about.

Fairness often involves equal outcomes (平等的结果)

Do monkeys behave in ways that lead to equal outcomes? To find out, scientists give monkeys choices about how to share food. Scientists ask a monkey to choose between two options—to provide a piece of food just for themselves, or to provide food for another monkey nearby, as well as for themselves (Figure 1). If monkeys are trying to achieve equal outcomes, they would give food to both themselves and another. Do they? Sometimes.

The left monkey has just chosen the board to give food to himself and the neighboring monkey.	The left monkey has just chosen the board that provides food for himself only.

Whether monkeys favor equal outcomes seems to depend on the species. The species which live in groups will prefer equal outcomes, but not all the time.

What else might be influencing whether monkeys create equal outcomes? If the two monkeys are friends, one is more likely to share food with the other. It also seems that monkeys would make the equal choice when they cannot see the actual food—some scientists use pictures of food.

But wait, does effort matter?

Scientists have developed a way to test whether monkeys prefer everyone to be paid equally for doing the same work. In this study, monkeys are trained to work for food by exchanging small coins with a scientist. To determine if and how monkeys respond to unfairness, scientists have two monkeys take turns exchanging coins and give them different food—their favorite food or a less-preferred food (Figure2). If the monkey getting the less-preferred food refuses to keep exchanging coins, scientists conclude the monkeys respond to unfairness.

The monkey on the left exchanges the coin for a piece of banana. Next, the neighbor monkey will also exchange a coin, but receive a less-preferred piece of food.

The results of the study have suggested differences across monkey species. Generally, monkeys living in groups do not respond to unfairness, while other monkeys do respond to it. However, monkeys do not appear to mind if they get a better food than others.

All in all, monkeys’ sense of fairness does not seem to be as well-developed as our own. By studying their preferences for fairness and responses to unfair situations, we can learn more about how these values developed in humans. And this also helps us to better understand the natural world and how to care for animals as well.

People realize that, although animals may not have the same intelligence as human beings, they are clever enough to learn certain things.

Dogs are extremely useful as companions for blind people. When a dog has been properly trained, he will always lead his blind master in the right direction and keep him out of danger. For example, seeing-eye dogs learn never to cross a busy road when cars are coming, even if their master ordered them to do so.

Horses are also able to learn many things. Horses that are used for guard or police duty must learn never to be frightened of noises and traffic. Racing horses are able to run much faster than other horses, but they are also quite tense. Therefore, it is necessary for those people who train them to be very patient and understanding.

The movie and television can use trained animals too. Some animals, such as monkeys and foxes, are easy to film. All you have to do is make a trail in front of the camera by putting something that smells good to the animals over the ground. Big animals, such as lions and tigers, can be photographed as they come happily back to their families or dinner. If a movie actor is nearby, the well trained animal will pay no attention to him. However, the audience may imagine that the actor escaped a terrible death.

Social distancing is not a new concept in the natural world, where infectious diseases are commonplace. Through specialized senses animals can detect certain diseases and change their behavior to avoid getting ill.

In 1966, while studying chimps (猩猩) in a Tanzanian national park, zoologist Jane Goodall observed a chimp named McGregor who had caught a highly infectious virus. His fellow chimps attacked him and threw him out of the troop. In one instance, McGregor approached chimps in a tree. He reached out a hand in greeting, but the others moved away without a backward glance.

“For a full two minutes, old McGregor sat motionless, staring after them,” Goodall notes in her 1971 book In the Shadow of Man. “It’s really not that different to how some societies react today to such a tragedy.”

Not all animals are so aggressive toward their ailing neighbors. Sometimes it’s as simple as avoiding those who may infect you.

When Kiesecker, a lead scientist in America, studied American bullfrog in the late 1990s, he found that bullfrogs could not only detect a deadly smell of infection in other bullfrogs, but healthy members actively avoided those that were sick. Bullfrogs rely on chemicals signals to determine who is sick or not.

Caribbean lobsters also shun diseased members of their community, well before they become infectious. It takes about eight weeks for lobsters infected with the deadly virus Panulirus argus mininuceovirus to become dangerous to others. Normally social animals, lobsters begin keeping away from the diseased as early as four weeks after infection – once the lobsters can smell certain chemicals released by sick individuals.

Overall, it’s important to note that, unlike us, animals don’t realize if they stay home, they might actually reduce the infection rate,” Kiesecker explains. “As humans, we have that ability. It’s a big difference.”