麻豆传媒

They can count, solve Aristotle鈥檚 logic puzzles and appreciate Impressionist art. Don鈥檛 underestimate the flying rat

FROM the piazzas of Venice to the sidewalks of New York City, the same refrain appears on signs the world over: 鈥淒o Not Feed the Pigeons!鈥� 鈥淲e just see them as a nuisance, flocking around McDonald鈥檚 and pecking all the French fries,鈥� says , who has studied pigeons for more than three decades.

It wasn鈥檛 always this way. Not so long ago, we stuffed Columba livia specimens for display in military museums, honouring them for their brave flights transporting messages across enemy territory. to help him hone his theory of natural selection, and was dazzled by their charms. Before a visit from his friend the geologist Charles Lyell, Darwin wrote: 鈥淚 will show you my pigeons! Which is the greatest treat, in my opinion, which can be offered to [a] human being.鈥�

Perhaps it鈥檚 high time to return those laurels. In addition to their well-known navigational expertise, it is now becoming clear that pigeons are capable of many impressive mental feats, in areas as diverse as memory, mathematics and art appreciation. The 鈥渇lying rat鈥� may even be able to outwit certain primates.

Urban pest or misunderstood genius? (Image: Plainpicture)

Pigeons probably owe some of their smarts to us. Humans first domesticated pigeons about 5000 years ago, breeding them for food and use as messengers. The pigeons seen roaming the streets today are the descendants of those domesticated birds. But even before we started nurturing them, pigeons were probably hanging around us, sheltering in our ancient dwellings and pecking at the plentiful grain in our fields.

Animals that have hitched themselves to human civilisations, such as dogs and rats, generally share certain features. They tend to be bolder than their wild counterparts. They also become generalists: rather than living in a well-defined ecological niche like a pine forest or a mountaintop, they have followed us into urban landscapes around the globe. To do so, their mental machinery had to become flexible. 鈥淎nimals that are able to adapt to living with humans show a larger degree of cognitively complex behaviours,鈥� says G眉nt眉rk眉n, who is at Ruhr University Bochum in Germany.

Those same abilities make pigeons great research subjects. It helps that they are widely available, inexpensive and easy to care for. 鈥淢ost importantly, they have the attitude of a civil servant,鈥� G眉nt眉rk眉n says. 鈥淵ou give them a job and for a bit of grain they鈥檒l work for hours.鈥�

The famed US behaviourist B. F. Skinner was one of the first scientists to notice these qualities. He became interested in the birds while training them to guide bombs for a secret second world war project. The project never came to fruition, but Skinner went on to establish a pigeon lab at Harvard University. Much as Darwin鈥檚 pigeons had shaped his theory of evolution, Skinner relied on his birds as he developed his theory of operant conditioning 鈥� the idea that behaviour is shaped by positive 鈥渞einforcement鈥� from rewards and negative reinforcement from punishment.

As important as they were, such mostly revealed bland, reflexive behaviours, says , who studies animal cognition at the University of Otago in New Zealand. 鈥淭hat was probably partly responsible for our perception that pigeons are not terribly bright animals,鈥� he says.

It鈥檚 a view Colombo once shared. He began his career in the US working with monkeys. When he moved to New Zealand, he didn鈥檛 have access to a primate lab, so he reluctantly switched to pigeons. 鈥淚鈥檇 be lying if I didn鈥檛 say I had a dim view of them,鈥� he says. That opinion didn鈥檛 last long, however. 鈥淚 turned around 180 degrees. They鈥檙e fantastic animals to work with.鈥� More than 20 years on, he is still extolling their virtues.

Those virtues include a phenomenal memory; pigeons can learn to recognise more than 100 images, and recall them more than two years later. They also have a head for numbers. A few years ago, Colombo and his colleagues showed pigeons pictures containing differing quantities of objects. The researchers trained the birds to peck first at the picture with one object, followed by the picture with two objects, and finally the picture with three objects.

Next, they showed the pigeons two new pictures, each featuring between four and nine items. Without any more training, the birds . In fact, they did just as well as rhesus macaques did on an identical task. Although this isn鈥檛 鈥渃ounting鈥� in the way we do it, Colombo says, it does show that pigeons and primates are equally good at understanding abstract numerical rules.

It isn鈥檛 the only example of pigeons thinking in an abstract way 鈥� a significant step up from the conditioned learning that Skinner studied. These birds understand 鈥渢ransitive inference鈥�, for example, which is a logic puzzle that Aristotle once pondered. If you know Mary is taller than John and John is taller than Anne, you can infer that Mary must be taller than Anne. Pigeons are able to apply this same line of reasoning to five individuals.

They can even recognise different styles of painting. at Keio University in Tokyo, Japan, . The birds were then able to generalise their knowledge, applying their understanding of Monet and Picasso to other impressionists and other cubists, respectively. Intriguingly, however, their visual system seems to work in a substantially different way to our own, making it difficult to imagine how they see these works (see 鈥淎 bird鈥檚 eye view鈥�).

鈥淭he pigeons applied their knowledge of Monet and Picasso to other impressionists and cubists鈥�

Aside from our art, pigeons keep an eye on our behaviour, too 鈥� perhaps unsurprisingly, given that we live in such close proximity. This was demonstrated not in the lab, but in a city park. Two people, similar in age, stature and skin colour but with different coloured coats that covered most of their bodies, fed the pigeons. One acted neutrally toward the birds, while the other chased them.

It didn鈥檛 take long for the pigeons to learn to avoid the hostile human. They still avoided that person even after the feeders switched coats, indicating that .

Such abstract learning suggests a certain level of intelligence. But there is much more to our own minds than an ability to notice patterns. We can plan for the future, for instance 鈥� giving our behaviour greater flexibility. Anecdotal accounts would imply that pigeons are also capable of planning in advance 鈥� think of the 鈥� that board the London Underground, wait a couple of stops, and then get off, day after day.

Although we can鈥檛 ever know for sure what鈥檚 going on in these birds鈥� minds, Colombo has some evidence that pigeons really can think about the future. In 2010, he trained a pair of pigeons to peck on three objects in a specific order: first a red circle, then a green clover-like shape and finally a blue dot. He then presented the same three objects to the birds, but with a twist. After they had pecked the red circle, the clover and dot suddenly switched places. If the pigeons had planned the entire pecking sequence at the start, one would expect them to take longer to peck on the correct objects while they updated their plan 鈥� and that is just what Colombo found.

In a second test, opaque white squares covered the clover and the dot immediately after the birds pecked the circle. Even without seeing the shapes they still pecked in , further suggesting they had formed a pecking-order plan from the outset.

Planning a step or two ahead may not sound too impressive. Yet the study suggests that pigeons aren鈥檛 just using a set of automatic responses. Somewhere in their brains, they appear to be thinking things through.

Along these lines, the spotlight has recently fallen on whether these birds are feathered philosophers, capable of a particularly sophisticated trait called metacognition. Also known as 鈥渢hinking about thinking鈥�, this awareness of one鈥檚 own knowledge is what allows us to judge whether we are certain of an answer on a quiz, or need to look up a word in a dictionary. It is often considered to be the apex of mental abilities by those studying animal consciousness. Although some primates and dolphins are thought to meet the grade, most animals fail.

Some enticing evidence came last year. Pigeons were trained to learn a series of three-item lists and peck symbols on a screen in a particular order. In some cases, the birds were given the option to peck on a 鈥渉int鈥� icon for help. They were more likely to ask for help when first learning a new list than during later stages of training. This suggests they were assessing their knowledge and . A similar study showed that pigeons sought more hints as they performed more difficult tasks, again implying that they have a handle on what they do and don鈥檛 know.

Yet other studies, including a series of tests by Sara Shettleworth, a psychologist at the University of Toronto, Canada, have found mixed evidence that pigeons can think about thinking. That鈥檚 why researchers including Colombo and Watanabe remain unconvinced. In Colombo鈥檚 view, the evidence for this advanced skill is somewhat suspect even in non-human primates.

Similarly tantalising, though inconclusive, clues may hint that pigeons have another form of self-awareness: self-recognition. To explore this trait, psychologists have long used the 鈥渕irror test鈥�, in which a researcher surreptitiously applies a spot of dye to the animal, then places it in front of a mirror. If the animal tries to rub at the dye on its own body, this suggests it is self-aware enough to grasp the idea of a reflection.

Apes, dolphins and even the magpie have passed the mirror test 鈥� but testing pigeons has been trickier. Given their grubby appearance, you may not be surprised to hear that pigeons aren鈥檛 particularly bothered by a mark on their feathers. So they first had to be trained to peck at dye spots marked onto their bodies. The researchers then marked body parts that could only be seen in a mirror. Sure enough, the pigeons used their reflection to locate the spot and peck accordingly.

For G眉nt眉rk眉n, however, that extra training makes it hard to draw firm conclusions. 鈥淐himps, orang-utans, elephants and magpies were never trained in this way. They just do it spontaneously,鈥� he says. 鈥淚 don鈥檛 argue that when pigeons look in the mirror they don鈥檛 have any sort of understanding that it is them. But the way we test pigeons doesn鈥檛 prove it.鈥�

Perhaps the decisive evidence will come from Watanabe鈥檚 lab. He has shown that a pigeon can recognise itself on video. The birds were trained to peck a keyboard when they saw themselves on live video feeds but not when they saw pre-recorded films of themselves. Then they watched more live video, but with a delay. They continued to peck, even when the video had a 2-second time lag. In other words, the , despite the time delay.

Recognising oneself on video is rare in non-human animals, Watanabe says; only apes, elephants and dolphins are known to possess that skill. What鈥檚 more, he thinks he has found evidence that pigeons can recognise themselves spontaneously in front of a mirror. That study, though, is still being reviewed for publication so he can鈥檛 yet discuss the details.

Whether or not pigeons are capable of thinking about themselves, it鈥檚 clear they are much smarter than most of us give them credit for. Does that mean we should raise them to the status of apes and elephants?

Don鈥檛 invest in a pigeon pedestal just yet. Many animals would probably be able to perform similar mental acrobatics, says G眉nt眉rk眉n, if we tested them systematically. 鈥淣ever underestimate the cognitive power of animals,鈥� he says.

To Colombo, the conclusion isn鈥檛 that pigeons are avian Einsteins, but that primates aren鈥檛 so special after all. As more and more animals are shown to perform mental tricks that rival our own, it all points to one question, he says: 鈥淎re humans unique?鈥� The loathed pest of city centres may suggest not.

This article appeared in print under the headline 鈥淲ho you calling featherbrain?鈥�