National Geographic

Intelligent Crows Flunk Causality Test (But Babies Pass)

You drop a block onto a box, and a toy pops out. If a baby was watching you, she could deduce that your action caused the happy arrival of the toy, because she understands cause and effect. She’d also realise that she could trigger the same event by placing a block on the box herself, because she can use her knowledge to actively shape her world.

These two abilities—understanding causality, and using that understanding—seem so simple and mundane to us that it feels weird to lay them out, and weirder still to separate them. But they are separate. That much becomes clear when you study an animal that can do one of these things and not the other.

The New Caledonian crow is one such animal. These birds are renowned for their intelligence, problem-solving acumen, and skill with tools. In their attempts to extract grubs from dead wood, they can choose the right tool for different jobs, combine tools together, and improvise from unusual materials. Their skills are impressive enough that many biologists have described them as “feathered primates”.

If these crows are so good at using tools, it stands to reason that they’d understand cause and effect very well. Auguste von Bayern from the University of Oxford showed as much in 2009: she found that crows that got food after pushing a platform with their beaks would then drop stones on the platform if it was placed out of reach. But these birds had experience–they had all previously pushed the platform themselves and been rewarded for their trouble. What happens without that experience?

That’s what Alex Taylor from the Universities of Cambridge and Auckland wanted to find out. He tested some crows with a similar task. The birds saw a Perspex box with several holes in it and a rotating cylinder inside. The first time round, a plastic block sat on a ledge above the cylinder, with a piece of meat attached to it. When the crows pecked at the meat, the block would fall and land on the cylinder, which would rotate and drop a second lump of meat onto the ground next to the crow.

The next time round, the plastic block was sitting on the ground outside the Perspex box. If the crows understood what they had previously seen, they would pick up the block, and drop it into one of the holes overlooking the cylinder. The block would land, the cylinder would roll, and a tasty hunk of meat would drop within reach.

Taylor tested five crows. All of them failed.

Over 100 trials, none of them dropped the box onto the ledge. “We thought they’d be good at this,” he says. “It’s interesting that they really, really struggle.”

It’s also interesting that human babies don’t struggle. Taylor’s team, including child psychologist Alison Gopnik, tested 22 two-year-olds with basically the same task, except with a marble instead of meat. Their initial attempts to reach a marble caused a block to fall off a ledge, rotate a cylinder, and dispense a second marble. The next time round, 16 of them dropped the block directly onto the ledge, within a few trials. They managed it, when the crows uniformly didn’t.

“We’ve got to test more crows and try different types of apparatus and behaviour,” says Taylor. “It’s hard to interpret a failure but given that we have the children passing with flying colours at age 2, for this particular paradigm, it’s pretty clear that the crows really can’t do it.”

The crows weren’t lacking in motivation; they were always quick to approach the plastic block and continued to do so over the course of the experiment. There’s nothing about the task itself that stops them, either. Taylor’s team found that they could train three other crows to drop the plastic block into the right hole, by walking them through the process and rewarding them at every step. They just won’t do it spontaneously; only the babies did that. We see, then do. They need to do before they can do.

This discovery highlights one of the important parts of Taylor’s study: he only worked with wild crows. His team captured the birds in New Caledonia, housed them in an aviary for a few months while they took part in experiments, and then released them. This means that, unlike many similar studies on animal intelligence, these birds had no experience with experiments and no training in the task they were tested on. “You’ve got these minds that evolved to function in the wild, so it’s important to look at the wild cognition if you can do so,” says Taylor.

The crows’ failure means that the ability to “create causal interventions”—that is, to do things that result in a desired effect—can be separated from the ability to understand causality in the first place. We have both; crows (at least as per this study) only have the latter.  “We have the complete package, so it’s really hard for us to know what’s particularly special and what isn’t,” says Taylor. “Studies like this provide a more nuanced view of what’s going on.”

Indeed, Taylor speculates that our ability to learn about causality through observation alone could have been one of the driving forces behind our success as a species. “It seems so obvious to a human but that’s almost the point,” he says. He’s now talking to colleagues who work with primates to see if our closest relatives can pass the same test.

Reference: Taylor, Cheke, Waismeyer, Meltzoff, Miller, Gopnik, Clayton & Gray. 2014. Of babies and birds: complex tool behaviours are not sufficient for the evolution of the ability to create a novel causal intervention. Proc Roy Soc B. http://dx.doi.org/10.1098/rspb.2014.0837

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There are 12 Comments. Add Yours.

  1. mV
    June 10, 2014

    I’m sorry, but how do we know that the crows understood the causual relation? we know that babies understood it, but only becuase they showed their understanding in their actions. but when there is no action, where is any proof of two seperate aspects?

  2. bomoore
    June 10, 2014

    How can one assume that a two-year old has no prior experience? They’ve been living with adult humans for two years, observing, copying, learning. It’s not a fair comparison.

  3. I_of_Horus
    June 10, 2014

    Why is there no upvote button, bomoore, because I would upvote your post.
    Maybe the real answer is raising kids in the wild for a few years and then expose them to the same test, though I doubt that _that_ experiment will pass an ethics committee. SMBC ran a comic about that a couple of weeks ago.

  4. Serge
    June 10, 2014

    Populations of Crows might differ culturally as well. It would be interesting to compare the population of origin of crows of previous studies. But again to conclude on the causality process of an entire species of Crow based on only five individuals… Seems far fetched statistically and biologically. I agree also with other comment that babies had experience with causality prior to the experiments.

  5. Bronwyn
    June 11, 2014

    Might there be a neurological difference underpinning this difference in behaviour? The only reason we learn as well by observation as we do is realIy mostly because of the mirror neurons in our SMA. Might it be worthwhile to consider the presence and/or role of a corvid equivalent of the SMA for tasks like this, I wonder?

    It also reminds me of a study involving dogs and wolves and who they pay attention to– if a crow sees another crow perform the task, would they learn it? As opposed to seeing the process happen when their own attention is on the meat, for example. Crows seem to think that when you’re engaged in eating, you can’t possibly be paying attention to anything else (it’s one of the best ways to get a shy crow to eat food you set down– to stick your face in your own food). I wonder if that’s their projecting their own single-mindedness in that particular respect? But I could be reading way too far into it.

    [Bronwyn, mirror neurons are the most hyped concept in neuroscience and far from "the only reason we learn as well by observation as we do. See these posts for more. - Ed]

  6. Badgerson
    June 11, 2014

    And still humans in general can’t grasp that causality does not imply correlation.

    Crows are probably not superstitious.

    And don’t hold a grudge for being called “a murder”.

  7. Dwayne LaGrou
    June 11, 2014

    It strikes me funny when I read all of the other replies to this.
    Just think how many people and even scientists did not, And some STILL do not believe in the causality of global warming due to the burning of fossil fuels!!! Sometimes they are just to darn STUBBORN to believe in a cause. By now most REAL scientists can see the overwhelming evidence of Global Warming and Climate Change due to the Human race burning so much fossil fuels and bringing the CO2 levels to over 400 ppm in the air.

    And we are wondering if CROWS can?!
    Just food for thought.

  8. Claud Pipkin
    June 11, 2014

    Yes….But did they test Ravens………….They’re supposed to be much smarter…..

    [New Caldeonian crows are reputedly the brainiest of the corvid family and the ones that have featured in the most experiments. Do you have a link for the raven claim? - Ed]

  9. Victory
    June 11, 2014

    Birds learn by watching other birds. So this experiment while interesting is a little lame. Crows learn complex manuevers by observation. Put a second bird in there that knows the drill and another bird will learn it. Birds learn, they do not need cause and affect, they learn by results.

  10. Anna-Maria
    June 11, 2014

    Maybe what we call intelligence isn’t just about brain size, but also or maybe even more about a certain security and standard of living. Tamed animals are known to be more playful and, let’s say, childish than those living in the wild. Maybe the curiosity that drives a creature to emulate what it sees is not just governed by intelligence but also by the carefree lifestyle of a well looked after baby or a crow that doesn’t have to struggle to survive day after day.
    It would be interesting to know wether babies who aren’t as pampered and cared for as Austrailian ones would react the same way.

  11. Jen
    June 12, 2014

    Interesting, but using wild crows skews the comparison. Human babies are taught hand/eye coordination skills at a young age, putting a block in a hole which then gives a reward (clapping adult, noise made, flashing lights go off). Babies, even at 2, are already trained for this, while a wild crow has no practical comparison.

  12. David Bump
    June 12, 2014

    TINY TOTS TRIUMPH IN TRICKY TEST! Crib crawlers’ cerebrums create causal celebration, crows crash.
    But seriously, I’m somewhat taken aback at all the negative reactions — it’s almost like people don’t want humans to be any different (let alone superior to?) any other creature, even one that was once an icon of low intelligence (“bird brain”), although in this case one of the geniuses of the class. On the other hand, I applaud the suggestions for further experimentation. Yet again, I doubt there will be such differences as some seem to think — birds have been observed to learn by watching humans (and other species) as well as other birds, these crows have shown that they are fully capable of manipulating things, in the wild as well as in the lab, and wild conditions are far more stimulating, challenging and filled with examples of important cause-and-effect events than some people seem to think. Maybe we should put some of you out in the woods for awhile and see how good you are at learning to survive by observing what goes on out there.

    Oh and: “He’s now talking to colleagues who work with primates to see if our closest relatives can pass the same test.” AAAARRRGHGH, yes! I should hope so! The first thing I thought of when I started reading — I don’t think I could have done the experiment without finding out about this before or during the trials, if at all possible.

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