Intelligence of chimpanzees (and other animals) in human terms

As I mentioned on another thread recently, I saw this TV show on Discovery about how chimpanzee societies work. Taking it all in, it seemed to be the case that chimpanzees seemed to interact with one another the way humans would if their mental development were arrested just before true speech begins. Chimpanzee dominance displays reminded me of toddlers’ temper tantrums – very loud and insistant, but nonverbal.

So has anyone ever attempted to evaluate the intelligence chimpanzees in human terms? For instance, has any expert ever said something like, “An intelligent chimp is about equal to a 3-year old human”? How about other animals? My wife thinks domestic cats can be about equivalent to a 2-year-old, but I think that’s a little generous.

To the kid or the cat?

Actually, that’s pretty much the currect opinion, in a nutshell. Most of the research in animal intelligence (and related subjects, e.g. language, theory of mind) is done with non-human primates. However, there have been some studies done on piping plovers (a kind of ground-nesting bird) to determine whether they have theory of mind – the knowledge that other creatures have thoughts and you can infer (and exploit) these thoughts through their behaviour. The results are inconclusive, but are sufficient to lead some researchers to give a tentative “yes.” Anyway, back to chimps. For a compelling read, check out “The Thinking Ape: Evolutionary Origins of Intelligence” by Richard Byrne.

A little generous? How many talking cats does your wife know?

I don’t think there is a valid way to compare animal intelligence to human intelligence. First of all the term intelligence is too broad. You can measure how well animals do at specific tasks, but what does that tell you? There are squirrels that can remember over 10,000 distinct places where they’ve hidden food. How many people can do that? Is the squirrel the smartest animal on the face of the earth then?

Asking where animals rank in terms of intelligence is not like ranking them in terms of speed, strength, etc. It’s easy to see which is the fastest… just measure how long it takes them to get from point A to point B. Asking which animal is “most intelligent” is more like asking which animal has the best teeth. It really depends what you want to do with the teeth. Sure, sharks teeth are sharp and all, but they aren’t very good for chewing lettuce. Similarly, human intelligence is good at language and calculating pi to 100 decimal places, but it’s not so good at remembering 10,000 hiding places, or even where you left the car keys.

We also don’t have very well defined definitions of intelligence for humans, so measurements of animal intelligence are shaky as well. The best you might be able to do is to test which animals have the most human-like intelligence, or which human traits they have (like the bird experiment mentioned by Nimue). I don’t think it would be a surprise if chimpanzees are it, as they are our closest evolutionary relatives.

There are a few behaviours that are generally reckoned to be pretty valid “proof” of intelligence. One example is recognising a mirror image as self - humans don’t recognise a mirror image to be themself until they are about 18 months to 2 years old. Parrots (probably some of the most intelligent bird species) don’t either - they often attack their mirror image if it is shown to them. Chimpanzees will recognise a mirror image as themself - using the image to help them groom etc… This is thought to be evidence that chimps are aware of their own existence as an individual.

Another interesting demonstration of chimp intelligence is that they are the only non-human species that has been demonstrated to actively lie. I can’t remember the source (sorry), but I read in a newspaper that a chimp in an American research centre, who had been taught sign language, was caught on CCTV defaecating in the chimps’ food bowl. When her keeper entered the room and asked (in sign language) who had done it, she blamed one of the other chimps.

I’ve used this story in another thread, but ask yourself this; what IQ would accurately describe both an animal and a human? The answer, IMO, is that there isn’t an IQ that will do that.

To use an example, a few years back my Dad and I were talking about the relative intelligence of our pets, and I asked him out of the blue, “What would a cat’s IQ be?” (He was a psych major.) After some discussion we realized that a cat has no IQ you can describe, not even zero. If you were to say a cat’s IQ is zero, that obviously doesn’t match a human zero, since a cat is a functioning, independent and highly adapatable animal with an advanced set of survival skills, while a human with an IQ of zero is a vegetable. So it is 60? Well, at 60 a human can perform some basic intellectual tasks like some basic reading; the world’s smartest cat can’t read. Below 60, the human is pretty much unable to function on their own, while the cat can.

IMO, tourbot is bang on; “intelligence” varies from animal to animal not just in quantity, but in quality as well. A chimp’s intelligence may be fairly comparable to a human’s because chimps are primates, but they’re still very different, and a dog’s intelligence is just completely unmeasurable by our own standards; some animals, like bees, are more like machines than thinking beings, but their brains function awfully well for the tasks at hand.

As tourbot and Cecil have pointed out, quantifying the differences in intelligence between species is not really possible.

Was this cat studying Freudian analysis, or Jungian? :smiley:

This is true; IQ tests are questionable enough when used with different groups of humans. You’ll never be able to make one which can fairly test different species. (An interesting aside – researchers once thought that a certain kind of fish wasn’t very “smart”, until they realised that they weren’t placing the stimulus where the fish could see it. They simply assumed it was in the fishs’ field of vision.)

However, this doesn’t stop comparative psychologists from trying. I already mentioned two of the areas they look at to get some estimation of intelligence – Theory of Mind and language. Another poster mentioned the ability to recognise one’s self in a mirror and tactical deception. There have been many ingenious studies on this, and a lot of them indicate that chimps are capable of intentional deception (which is a key piece of evidence for ToM – after all, you can’t intentionally deceive someone without being aware of their erroneous thoughts). But there are plenty of skeptics who point out ways in which the chimp could be performing this way without trying to intentionally deceive the other chimp/researcher. When it comes to proving another species has ToM, ultimately we may never be able to, because we will never actually know what goes on in their minds.

Another way of looking at intelligence in non-human primates is through tool use. Most chimp societies in the wild make tools for various purposes to suit their environments. These include things like sticks to fish out termites or ants, leaf sponges to soak up water in hard-to-get places, and the use of particular types of rocks to break open seeds and nuts. They also examine useful behaviours such as washing sandy food. Researchers are particularly interested in tool-use not just because of the proficiency it requires, but also to look at how these techniques might be socially transmitted, i.e., how do chimps learn these behaviours from one another. Mimicry? Imitation? Purposeful teaching (e.g. to offspring)? They’ve also looked at this in chimps in captivity, most notably with Washoe, a chimp who (mostly successfully) taught her adopted chimp baby how to sign.

Lastly (I could go on forever about this), a more quantitative way of looking at “intelligence” in animals is to infer it through relative brain size. Comparative psychologists do this through a method called allometric scaling. Basically, for each particular group of animals one wishes to compare (e.g. primates, mammals), brain size is plotted against body size in such a way that you can determine which animals in the group stand out with relatively large brains for their size, and which lag behind the rest of the group. In the primate example, we see that humans have brains three times larger than what we would expect of an ape of human bodily size. And yes, this method sure does have its limitations. But it is at least some sort of quantitative measure of brain size, which is closely related to intelligence (in inter-species terms at least).

Given all the various information that has accumulated about the intelligence-related abilities of chimps, researches generally summarise that the most intelligent chimps are roughly similar to 3-year-old humans.

Btw, all of this and more is explained in the book I referenced above (Byrne’s “The Thinking Ape”). Very interesting stuff. Almost makes me want to go on and do a PhD in comparative psychology.

He never got past first year, because he kept spraying on the exam papers. :smiley:

Tourbot, that is a wonderful sig. Bow deep and low in respect. Did you hatch it, or is it from something?


            Originally posted by javaman


                   Originally posted by RickJay
                   To use an example, a few years back my Dad and I were talking about the relative intelligence of our pets, and I asked him out of the blue,
                   "What would a cat's IQ be?" (He was a psych major.)

            Was this cat studying Freudian analysis, or Jungian?

     He never got past first year, because he kept spraying on the exam papers.

I had the same problem, so I switched to English.

Try listening to “Where Your Eyes Don’t Go”, on They Might Be Giants’ album “Lincoln”.

I read about an experiment that was done on Apes to test their intelligence. The scientist put a screw driver or some other object in the apes’ cages and reported their findings.

Supposedly they concluded:

A gorilla would ignore it.
A chimpanzee would use it as a crude tool for eating or something.
An orangutan did one of two things. If the orangutan noticed that the keeper knew/saw the tool in the habitat, the orangatan would try to trade it for food or other treat. Like saying “I found your screwdriver, what do I get for it?” If the keeper was never around or never looked at the object, the orangatan would ignore it until after dark. Then he would use it to open the lock on the gate.

I am a little sketchy on details, but it was pretty interesting and pretty funny too.

While we’re on this subject, does anyone know if octopi can recognize their reflection? I’ve heard so many things about how intelligent they are. Are they also self-aware?