23 December 2011

(125) Cleverer than a child of four.

Cleverer than a child of four, the birds who can read your mind

Fascinating experiment shows members of the crow family, known as corvids, aren’t just among the cleverest birds, they are smarter than most mammals
By Nicky Clayton


Aesop had the measure of crows.

In his fable, there was a wise old mother crow who finds a pitcher with only a little water in it.
Desperately thirsty, the intelligent bird drops small stones into the container, raising the water level until it is high enough for her to drink.

The story might be 2,500 years old, but the Ancient Greek author clearly understood how the crow’s mind works.

For when we recreated the experiment in our laboratory in Cambridge, the birds did exactly as Aesop described. Without being taught the details of the task, they picked up stones and dropped them into a tube of water — raising the water level.

This experiment is part of a research programme which has proved that members of the crow family, known as corvids, aren’t just among the cleverest birds, they are smarter than most mammals.
In fact, their intelligence rivals that of apes — who, along with crows, are able to do tasks that three and four-year-old children have difficulty with.
I’ve been fascinated by birds for as long as I can remember, and for me, the magic lies in their movement.

The Aesop’s fable experiment was designed to see if corvids (the family of birds that includes crows, jays, ravens and jackdaws) have causal reasoning — the awareness that one event leads to another.

In our study we placed a wax worm — the larva of the wax moth, and a favourite snack of corvids — on the surface of the water in a tube, just out of reach of the crows’ beaks.

When we presented the birds with the tube and a pile of stones, they put stones into the tube to raise the water level, until they could reach the worm. Later, we gave them just the tube and the wax worm — and they flew off in order to get their own stones.

In other experiments we gave two of our jays — the highly intelligent and charismatic Romero, and smarty pants bully-boy Hoy — a choice of two types of object: dense rubber ones that sink and foam ones that float.

After they’d had some time to play with the objects, they worked out that it was the rubber objects they needed to put into the tube to have the same effect as the stone. They did not make the right choice all of the time but they dropped the rubber objects in many more times than could be attributed to chance.

What is amazing about this is that these birds are not natural users of tools in the wild, so this is not a skill that natural selection has crafted over the centuries.

I don’t know whether the birds use the weight or the texture of the objects to decide which will raise the water level, but when we did a similar test with children aged four to ten, the younger ones didn’t work out the solution.

Yet another experiment has shown that birds have what is called ‘theory of mind’ — in short, the ability to see the world from another bird’s point of view.

Out in the wild, jays and other corvids will hide food in the ground. We experimented with them, hiding food in two types of tray — one full of pebbles which was noisy when disturbed, and another full of sand which was quiet.

If other birds couldn’t see them hiding the food because they were behind a screen, but could still hear them, the jays picked the sand and were as quiet as mice when they buried food. But if other birds were watching, or if they were on their own, they realised that it didn’t matter how noisy they were.

This looks like very intelligent behaviour — deducing what others will or will not know from what they have seen and heard. Of course it could be an evolved instinct, because birds need to hide food to survive.

But there’s a second more striking example of their intelligence — one which instinct alone cannot explain.

If the birds were being watched when they hid their food, they rushed to move it to another hiding place as soon as the other watching birds were out of sight.

However, they did not bother doing this if no other birds had actually seen them hiding the food. And crucially, the birds only moved the food after they’d been watched if they had experienced theft in the past — if another bird had stolen food from them or if they have seen another bird steal food.

Since there are also hand-raised birds in our care which have never experienced theft and which never move the food, this rules out blind instinct and proves that such behaviour is learned.

A third experiment showed that birds have the ability to plan ahead.

Results showed hand reared birds who have never experienced theft so never move or hide their food (pictured are a pair of Green Finch, not included in the experiment) in a suite of three interconnected rooms for a period of six days. At night, the bird was locked into one of the three rooms.

In the morning, food was served in one room but not in the others. For the first three nights, we put the bird in the room where no food was served in the morning. For the next three nights, it was put in the room where food was delivered.

Then, we gave the bird the opportunity to plan ahead, by giving them enough food for one meal and some surplus.

We wanted to know if they would remember which room didn’t come with breakfast, and realise that they should stash the food in that room for the next morning.

We found that the birds stashed food in the ‘cheap motel’ room — even though there was only a 50-50 chance that they were going to spend the night there. This sort of planning ahead is not trivial — young children struggle with it.

There are many examples of corvid intelligence from around the world. In the wild, New Caledonian crows use twigs to reach insects in crevices.

But in a study at Oxford, a New Caledonia crow called Betty went further and took a straight piece of wire, fashioned it into a hook and used it to get food. Faced with an old problem, she worked out a new solution. And our rooks are able to do just the same.

Not all birds are as clever as crows, although parrots might be quite smart.

These findings have fascinating implications.

People used to believe that the high level of intelligence we see in humans and apes evolved only once on the planet, but if it occurs in distantly related groups — the common ancestor we share with birds lived 300?million years ago — it suggests this intelligence evolved more than once.

This means that we may have other intelligent lifeforms on earth that we are not aware of. And because birds’ brains are very different from mammal brains, it raises questions about what kinds of brains support intelligence.

There are other contenders for considerable intelligence in mammals — such as dolphins and elephants. What they and birds all seem to have in common is that they are long-lived and have huge brains relative to body size.

These birds have long ‘childhoods’, with lots of opportunities to learn from parents. And they are all highly social.

It has been argued that one thing that gives rise to intelligence is living in social groups. It means you have to think about what others are doing all the time.

As mammals, we have overlooked the intelligence of non-mammals. Perhaps we should show more respect — for if evolution had unfolded differently we humans might have been mere curiosities to our beady-eyed corvid masters