If the gift-giving habits of jays are anything to go by, we may be surrounded by birds whose minds are in some ways remarkably similar to our own.

Male Eurasian jays, a common member of a bird family that also includes blue jays, crows and ravens, passed a food-giving test of whether they knew what their mates wanted to eat.

That deceptively simple ability hints at what scientists call a "theory of mind," or a nuanced awareness of other individuals' thoughts and feelings.

"It was long thought that only humans could do this. What we've shown in a series of experiments is that doesn't seem to be the case," said comparative psychologist Nicola Clayton of England's University of Cambridge.

Clayton's findings, published Feb. 4 in Proceedings of the National Academy of Sciences, are the latest to chip away at the notion of humans as singularly exceptional, possessing cognitive abilities unprecedented in the animal kingdom.

That notion didn't always hold sway, and in some ways corrected the excessive anthropomorphism of the 19th century, when such august figures as Charles Darwin ruminated on the maternal affections of starfish and earwigs.

The pendulum swung back in the 20th century, to the point that now-famous primatologist Jane Goodall was originally mocked for thinking chimpanzees, humankind's closest relative, had human-like feelings.

We now know that chimps do have such feelings, not to mention tools, another formerly human-singular capacity also seen in dolphins, elephants and even fish. Indeed, the last decade of animal behavior research seems like a parade of findings that animals are quite complicated beings. Even honeybees seem to have emotions.

A theory of mind, however, is generally still considered uniquely human. Experiments have suggested its existence in great apes, but these remain open to alternative interpretations. That birds might have a theory of mind is a remarkable claim.

In the new study, researchers led by Clayton and fellow Cambridge psychologist Ljerka Ostojić decided to study whether Eurasian jays understand that other jays have their own desires and motivations, an ability known to cognitive scientists as "state attribution." It's not in itself a full-blown theory of mind, but it's a key component.

Given that researchers can't communicate directly with jays, their state attributions are difficult to discern, but Clayton's team took advantage of male jays' gift-giving habits. To win favor with mates, they give them food. "If you look at people, gift-giving is one of those great theory-of-mind tests," said Clayton. "If you're good at giving presents, it's quite a good test of what you know."

The researchers allowed male jays to watch as their mates, separated from them by a screen, ate their fill of either moth larvae or mealworm larvae. The males could then offer either a single mealworm or moth through the screen as a gift.

For jays as well as people, variety is valued: A jay that's gorged on moths will generally prefer to eat mealworms afterwards, and vice versa, just a person satiated by chocolate will next take a slice of cake.

The male jays' choices bore that awareness out. After watching their mates eat one type of food, the males consistently made gifts of the other. Based on what they'd observed, they knew what their mates would want. Importantly, females didn't communicate a preference. When their meals were hidden from sight, males failed to give the desired gift.

The benefits of knowing a partner's mind are obvious, wrote the researchers, who framed an analogy in Valentine's Day-appropriate terms of a man who gives chocolates to his wife.

"The giving and receiving of chocolates is an important pair-bonding ritual, and as such the wife may be unlikely to reject the chocolates whether or not she currently wants them," they wrote. "However, a man that makes sure that he gives his wife the chocolates she currently really wants will improve his bond with her much more effectively."

While state attribution is just one piece of a theory of mind, research suggests jays possess the other pieces, too. Clayton's earlier work showed that food-stealing jays hide food from jays who've watched them, but not from jays who haven't. They seem to know that other birds can learn.

Jays also seem to plan for the future and consciously follow other jays' gazes. In humans, these abilities don't come together until around age four.

As for whether jays make state attributions about individuals other than mates, or about other species, it's hard to say. Jays only give gifts to mates, so the tests haven't been run. The same holds for whether other birds and other animals share the jays' nascent theory of mind, a proposition that Clayton warned against assuming to be true.

At the same time, though, Clayton cautioned against assuming animals to be unintelligent. There's an inevitable gap between what's known and what's been demonstrated experimentally. "Who knows? It's not being tested," she said. "Absence of evidence is not evidence of absence."

The ultimate importance of the work, Clayton said, is the richness it implies for the world around us. She referred to corvids as "the ape in your backyard." Evolutionary anthropologist Brian Hare of Duke University echoed her words.

"This is another piece of evidence in support of the idea that corvid cognition converges with that of the great apes," said Hare. "Just like fish, dolphins and penguins all evolved flippers independently to deal with ocean living, it seems corvids have evolved intelligence that rivals that of our own ape family."

"We're all blown away by what chimpanzees and bonobos can do," Clayton said. "Most of us aren't going to see a chimp in their natural habitat. But there are these other versions of intelligent life in your backyard, or just down the garden path."

Video: Tests of whether male Eurasian jays know what their mates want. (Ostojić et al./PNAS)

Citation: "Evidence suggesting that desire-state attribution may govern food sharing in Eurasian jays." By Ljerka Ostojić, Rachael C. Shaw, Lucy G. Cheke, and Nicola S. Clayton. Proceedings of the National Academy of Sciences, Vol. 110 No. 6, February 5, 2013.