Why do most of us work together for the common good, even when it might personally benefit us more to cheat? Is it because we fear we would be punished for not following the rules? Because we have been taught to treat others as we would want to be treated?

Because cooperation is vital for survival in a variety of contexts, it may be that fair play is an evolutionary adaptive behavior, scientists say. Of course, the flip side is that when an individual does behave selfishly, others often use some form of negative reinforcement to dissuade such behavior in the future.

It appears animals do the same. First, though, an animal must recognize unfair situations. To find out if primates can do so, Dr. Sarah F. Brosnan of Georgia State University and her colleagues set up a series of experiments in which pairs of primates were trained to perform the same task, but one received a much tastier reward. Brosnan discovered that they do realize (and respond negatively) when another primate receives a "better" reward for completing the same task. Even when they get the same reward they did before (in the control situation) that they were happy with, the animals will not be satisfied "if a partner gets a better deal," Brosnan and Dr. Frans B. M. de Waal say in their article. Primates "clearly have to be able to assess quantities or qualities and compare them, so there is a baseline level of cognition which is required," said Brosnan.

Sometimes, certain primates will refuse food rewards that they deem insufficient. Like petulant children, primates have been known to toss the reward from the test chamber. "When I began the research, I never expected to see individuals refusing food rewards," Brosnan said.

So, what about the other animal, the one that who received more food? Even though they were better rewarded, these chimpanzees refused to participate more often than when the food was distributed more fairly. Is this due to a sense of justice? Or just a desire to avoid retaliation (in other words, punishment) from their partner chimp after the experimenter leaves?

In a similar study using dogs as subjects, when two dogs performed the same task and one dog received a reward when the other didn't, the "slighted" dog recognized the unfair treatment and began to refuse to obey the experimenter. However, unlike the primates, the dogs did not seem to notice when the other dog received a larger or better reward, as long as they both received something.

Although we might expect it of our primate relatives, and even dogs who spend so much time with humans, it seems humble fish also recognize when they're being cheated. Cleaner fish, as the name implies, remove dead skin, parasites, and other bits of junk on larger "client" fish. However, the fish tend to prefer the healthy scales and mucus to the dead cells, so they will sometimes "cheat" and bite the body itself of the client fish. Naturally, these bites often cause the client to swim away, thus depriving the cleaner fish (and their cleaning partners) of a meal.

Image courtesy of João Paulo Krajewski.

Raihani and her colleagues tested the fish in the laboratory to simulate conditions in the ocean. To represent client fish, they prepared a plate of food with both fish flakes (which cleaner fish like okay) and prawns (which the fish love). A low-value plate had four fish flakes while high-value ones had eight. The experimenters put a plate of food in front of each pair of cleaner fish (one male, one female). They were allowed to eat as many of the fish flakes as they liked, but as soon as one of them ate a prawn, the plate of food was removed (to simulate the client fish swimming away). The researchers then measured the level of punishment (aggressive chasing) that the male doled out to his partner.

Can elephants smell danger? Dr. Lucy Bates and her colleagues at the Amboseli Trust for Elephants demonstrate that elephants have a unique combination of cognitive capacities: great senses of smell, impressive memories, strong social bonds and relatively sophisticated communication skills.

"People often think of elephants as being very intelligent," Bates said. "The research so far does support the old adage that elephants have good memories ('elephants never forget') but the evidence also suggests that elephant memory is far more impressive and complex than simply remembering lots for a long time."

Image courtesy of Tom Curtis/FreeDigitalPhotos.net. African Elephant.

Bates wanted to find out if elephants utilize their powerful memories to recognize potential threats. The more than 1400 African Elephants (Loxodonta africana) in the Amboseli National Park in Kenya encounter various humans, including members of two ethnic groups, the Maasai and the Kamba.

The Kamba people, agriculturalists who eat a variety of foods such as meat, vegetables, and maize meal, don't hunt or otherwise hurt the elephants. On the other hand, young Maasai men, who traditionally wear bright red garments, have been known to spear elephants, especially those elephants that attack the Maasai cattle. Maasai culture relies on cattle; the Maasai drink cow's milk and eat cow meat and blood and use animal fat as body paint. Further, because their animals are so important to their survival, they often keep them inside their villages and even in their homes. Such close contact with cattle "does give their homesteads a distinctive smell and I think it is also reflected in their body odor," said Bates.

To discover whether elephants associated these distinctive smells with the two ethnic groups, Bates and her colleagues studied the elephants' reactions to three different shirts: one unworn, one worn by a Maasai man for five days, and one worn by a Kamba man for five days. The researchers then placed the shirts in a field and set up video camera to record the elephants' reactions.

Next time someone calls you a birdbrain, just say, "thank you." Research indicates that members of the crow family are more intelligent than chimpanzees, at least in certain ways. Perhaps this shouldn't surprise us; there are certainly clever birds in folklore. Here's an example:

"In a spell of dry weather, when the Birds could find very little to drink, a thirsty Crow found a pitcher with a little water in it. But the pitcher was high and had a narrow neck, and no matter how he tried, the Crow could not reach the water. The poor thing felt as if he must die of thirst. Then an idea came to him. Picking up some small pebbles, he dropped them into the pitcher one by one. With each pebble the water rose a little higher until at last it was near enough so he could drink."

This familiar fable was probably intended to tell us more about ourselves than about crows. Just as we don't expect a mouse to repay a kindness to a lion by nibbling through the robes that bind him, we don't hear this story and then assume that a bird can employ this level of intelligence to earn itself a drink.

Image from The ÆSOP for Children, Illustrated by Milo Winter. The Crow and the Pitcher.

However, it appears we may be underestimating that crow. The rook (Corvus frugilegus), a bird in the same family as crows, ravens, and blue jays, has a brain the size of walnut, but can perform some tasks that confound even our chimpanzee cousins. Dr. Nathan Emery, a researcher at Queen Mary University of London, and his colleagues demonstrated that when confronted with a container of water with a worm floating out reach of their beaks, rooks figure out how to drop rocks into the water to raise the worm high enough for them to reach it. Even more impressively, they know how many stones to use and realize that large stones accomplish the task much more quickly than small ones.

That these birds can solve the puzzle the first time they see it--which not even all primates can do--must "change people's perceptions of what birds are capable of," Emery said. "They are no longer bird brains, but feathered apes."

The fact that rooks do have these capabilities is interesting enough, but researchers want to know how they do it. How does their intelligence relate to brain size and structure?

Neuroscientists love to talk about structure equaling function. In other words, if an animal demonstrates an ability, a behavior, there must be something in its brain that allows it to happen. In this case, birds have brains that are much smaller--and differently structured--than those humans or apes. Emery wonders if there is something in this brain structure that can process information more efficiently than the primate brain does, thus allowing the birds a great deal of cognitive processing with a relatively small neural volume.

Image courtesy of Paul Brentnall/FreeDigitalPhotos.net. Rook.

Rooks demonstrate "flexible intelligence," Emery said, meaning they can adapt to different environments. The birds Emery used in his studies were raised in captivity, with everything they needed provided. Did this environment allow them to focus their cognitive abilities on other things, such as solving the puzzles scientists put in front of them? Wild birds too have to face new challenges as they increasingly live in urban environments, where "we may be seeing an example of cognitive evolution 'in action,'" Emery said. Over many generations, city living may fundamentally change these bird brains. In the shorter term, birds may pass their cognitive skills on to their offspring through social learning. In this, rooks seem to demonstrate the same neuroplasticity (the brain's ability to change, both structurally and functionally, as a result of the environment) as their cousins the songbirds. The brains of these birds have been shown to generate neurons at certain times of the year, in response to reproductive or environmental pressures that require increased cognitive capacity.

And what does all of this tell us about ourselves, when even birds have cognitive abilities that we once thought were uniquely human, such as the causal reasoning demonstrated by Emery's rooks? Professor Nicky Clayton of the University of Cambridge has shown that the Western Scrub Jay (another member of the crow family) is capable of mental time travel (remembering the past or imagining the future) and theory of mind (the ability to guess what another individual is thinking or feeling)--both of which are generally thought of as sophisticated cognitive abilities. Perhaps these demonstrations of animal intelligence indicate that we are not as exceptional as we would like to believe.

Clayton, who also happens to be Emery's wife, talked with NOVA about her work and why she thinks birds are intelligent.

This post is part of the series Animal Acumen, an exploration of animal cognition. Visit other posts in this series.

This is a preview of a series of posts about animal cognition.

Read Part 1: Feathered Apes
Read Part 2: Elephantine Intelligence
Read Part 3: Cooperation and Punishment

We have often stereotyped animals with human-like traits: the wily coyote, the wise owl, the stubborn donkey. Children's stories and fairy tales are full of talking animals and our literature has works, such as Animal Farm, in which animals acting like humans teach us about ourselves. Many pet owners think of their animals as their children and credit them with similar levels of intelligence.

Now researchers, from neuroscientists to behavioral psychologists, are investigating in a methodical way animal cognition, or the way animals "think."

Interestingly, we haven't been entirely wrong in our lay assessments. "The animals that have always been popularly perceived as intelligent do turn out to be so when we psychologists come along and test them," said Dr. Lucy Bates. "Elephants, dolphins, crows, and monkeys, for example, are all perceived as being smart by various cultures or traditional stories, and now the science is just catching up to this. I think it is brilliant that hundreds or even thousands of years ago, people were able to make conclusions about these animals just from watching them in their natural environments, and the stories and legends were passed down the generations."

But now we can begin to address questions about why these animals are so smart. Neuroscientists believe that thought or behavior (i.e. the brain's function) must be mirrored in the brain's structure. Animals, especially our primate relatives, have brains that are, in many ways, similar to ours. Thus, animal behavioral researchers tend to come back to one theme: What can the behavior of these animals tell us about what makes us human?

"Although it is fun to ask whether an animal can do the same as humans, that's not the bottom line for me," said Dr. Nathan Emery of Queen Mary University of London. "I'm interested in how cognition evolved and the conditions which allowed it to evolve in a wide variety of species facing supposedly similar challenges in their day-to-day lives - how to find, extract and process food, how to deal with other members of your social group, how to deal with massive fluctuations in habitat and climate, etc. We see that all 'clever animals' (apes, cetaceans, parrots, elephants, etc) have to deal with these same challenges in a flexible manner."