Sunday, 6 October 2013

How Clever is a Baboon?

Humans were long considered quite different from the rest of the animal kingdom based on the fact that they're considerably smarter. While we now know that, biologically speaking, we're no different from any other animal, there remains no question that we are quite a bit more intelligent. This is why we're the dominant species on Earth - at least, assuming you happen to use human-biased definitions of 'dominant'. (There are other senses in which, say, bacteria have us beat hands down).

Anatomically, the clearest sign of this higher intelligence is the size of our brains. Relative to the rest of our bodies, they are huge, and they're also considerably more complex than those of many other mammals, let alone reptiles, fish, or insects. The 'relative' part is important, though. An elephant's brain is much larger than that of a human, and those of whales are larger still. Now, granted, elephants and whales are among the most intelligent of mammals, but it's not as if they've discovered quantum mechanics or (that we know of) have composed the equivalent of Dante's Divine Comedy. Their brain is large in part because they are large, and, when you allow for the size of the bodies, it's really not all that big in proportion to the rest of them.

On the other hand, when it comes to brains, as with certain other organs, size does matter. The brain of a mouse is, in proportion to it's body, almost exactly the same size as our own. (And something like, say, a chaffinch, has a brain that's even larger). Clearly, there is a minimum size below which you just can't fit all that much into a brain, in terms of neural connections and the like.  Smaller animals, therefore, will have proportionally larger brains, just in order to function.

We can allow for this by mucking about with the maths to give a number that relates how large the brain actually is compared with what we'd expect it to be for a mammal of that overall body size. This is called the encephalisation quotient, and, essentially by definition, for most mammals, it's about 1. (That is, most mammals have a brain that's about as large as we'd expect it be for a mammal of their size. Which is hardly a shock). Herbivores and things like shrews, tend to have a lower number - possibly because you don't to be brainy to outsmart a vegetable - while cetaceans, and, yes, elephants, tend to be higher.

While dolphins do score very highly indeed, among land mammals, it is our own order, the primates, which do best. And, within the primates, it is the great ape family, to which we ourselves belong, that comes out on top. But why - what is it about primates, and great apes in particular, that led to the evolution of such large brains? And just how much does our brain size have to do with our smarts?

To understand the origins of human intelligence, in the absence of living australopithecines, and the like, we have to look to our closest relatives. There has been, for example, quite a lot of work on the intelligence of chimpanzees, and on the other great apes, the gorillas and orang utans. This is clearly all very relevant to where we ourselves came from, but can we push it back further, and see how great apes compare with their own relatives, giving us a longer trail to follow?

The closest relatives of the great apes, are the "lesser apes", members of the gibbon family. Next after them comes the Old World monkey family, comprised of a range of African and Asian species. Their brains are smaller than those of apes, but, with an EQ of around 2, still very large compared with most other land-dwelling mammals. So how do they stack up against apes in the intelligence stakes?

There are, of course, many different ways of measuring intelligence, not least because it isn't a single thing that we can give a value to, anyway. There are different kinds of intelligence, and animals that score well on one test might not do so well on another. This would explain why, although some studies have shown that great apes are, as we'd expect, more intelligent than monkeys, others have found that there's really not much difference between the two.

One fairly broad measure of primate intelligence is the so-called Primate Cognition Test Battery. This has been used, for example, to compare adult chimps and gorillas with two-year old humans. As its name suggests, it's a standard set of tests, designed to illustrate a range of different forms of intelligence, rather than just one. (I do not, of course, suggest that it's the only way of doing this, or even necessarily the best, but one has to start somewhere).

In total, the battery is designed to compare three kinds of 'physical' intelligence, and three kinds of 'social' intelligence. Physical intelligence refers to the animal's ability to understand concepts of space, quantity, and causality. For instance, if I place a piece of food under a cup on a table, and then rotate the table through a 180 degrees, can you remember which cup the food is under? That's spatial intelligence.

For quantity, can I tell that five bits of food is better than four bits of the same size? It sounds simple enough to us, because adult humans can quite easily tell that five apples are more than four, just by glancing at them. But it gets a lot tougher, even for us, if we're trying to compare sixteen objects with seventeen, and aren't allowed the time to count. For non-human animals, the point at which they lose the ability to distinguish between similar numbers happens much sooner than it does for us.

Causality intelligence can range from the relatively easy - if I hide a peanut under a thin cloth, can you figure out which cloth it is by looking for the lump? - to what we often think of as one of the pinnacles of human intelligence, namely tool use.

Social intelligence deals with how animals relate with one another, or, at least, within the context of the test, with human experimenters. (This may, of course, be a limitation, if the monkey understands basic social concepts, but not that they can apply to other species, such as humans). Here, the battery looks at whether the animal can learn by imitating others, whether it can understand gestural communication, such as pointing, and whether they can understand the intentions of others.

Pointing seems to us such a basic concept that it's easy to forget what it entails. Point your finger at something, and most animals will look at, if anything, your finger. It's your finger that's doing something, after all. But some animals - notably including dogs - can grasp the more abstract concept of "over there" that you're trying to convey.

Finally, to demonstrate an understanding of intention, the animal has to figure out that you have spotted a piece of tasty food that it hasn't, from the way that you act (trying to get the lid off something it's in, and then failing, for instance).

When the apes were tested against 2 year-old children, they did about equally well on the three measures of 'physical' intelligence. However, even the children were able to beat them on the social tasks. Which may show how our intelligence evolved, and what it is that's so different about it: it's our social skills and our ability to cooperate and pass knowledge on that really set us apart. All of that requires a real understanding of the minds of others, and it may well be that, rather than tool use, that's a defining feature of human intelligence. Chimps, for instance, are, by human standards, incredibly selfish, and have a hard time cooperating to solve a problem.

So what about monkeys? The test battery was recently used on crab-eating macaques (Macaca fascicularis) and olive baboons (Papio anubis), and compared against the results obtained from apes. Both species of monkey failed miserably on the tests of tool use, apparently quite unable to comprehend the idea of reaching for things with sticks, which is what the test uses. It's worth noting that crab-eating macaques, at least, do use basic tools in the wild - they whack crabs with stones to open them, for instance - so it may just be sticks that are beyond them. But even so, a failure is a failure.

In other respects, though, there wasn't a lot of difference between the apes and the monkeys in terms of 'physical' intelligence. In terms of social intelligence, the picture is less clear. They failed completely on the "learning" task, being unable to imitate a human experimenter, but were actually better than the apes when it came to things like following the gaze of humans, and about the same on the other measures. Perhaps, since they both live in large groups, social intelligence is more important to baboons and macaques than it is to chimps and gorillas, which live in smaller families, let alone the relatively solitary orang utans.

In general, we can say that the monkeys did rather better than might have been expected on a number of tasks, based purely on the size of their brains. The two species didn't perform identically, either. For instance, baboons are apparently at better one of the spatial tasks. This may relate in some way to their very different native habitats and lifestyles (macaques in the jungle, baboons on the savannah), although it's not terribly obvious why.

But what it may show is that brain size alone isn't the sole determiner of intelligence. Monkeys are supposed to be less intelligent than apes, and in some respects, they probably are. But, in other respects, they may be at least as good, if not better. Yes, this seems to show that certain forms of intelligence, especially relating to tool use and learning, are more human-like in apes than they are in monkeys. But that's not the only form of intelligence there is.

In some respects, baboons are more clever than we thought.

[Photo by "Haplochromis", from Wikimedia Commons]

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