Editorial: “A question of intelligence“
ANYONE who has pets suspects that some animals are smarter than others. Now, in tests on apes, systematic differences in intelligence have been found, similar to those discerned by IQ tests in humans. And one chimp seems to be off-the-scale smart compared with her peers – perhaps the first known chimpanzee prodigy.
The findings could help explain the differences between animal and human intelligence.
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and of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, pulled together data from a decade of studies on two groups of captive apes: a group of 30 living in Leipzig, including chimps, bonobos and gorillas, and 106 chimpanzees from two African sanctuaries. Over the years these animals had been tested on a range of mental abilities, from spatial reasoning and tool use to social learning and communication.
Among the Leipzig apes, three performed consistently better than the others across all tasks, but not by much. Seventeen of the African chimps did consistently better, and one – named Natasha – was off the chart (Philosophical Transactions of the Royal Society B, in press). She joins a long list of animals touted as prodigies (see “Animal Einsteins”).
Wisdom of age
It is fascinating that Call and Herrmann were able – for the first time – to document individual variations across a range of animal intelligence tests, says .
In a study of 42 different species, Thornton identified some factors that could help explain why some individual animals do better than others at cognitive tests. By comparing data from 118 previous studies, he found that adults generally outperformed juveniles, perhaps because they had more experience, and animals raised by humans outperformed those reared by their mothers. He presented his findings in January at a in London.
However, neither age nor exposure to humans explains Natasha’s high scores: she was the same age as the chimps she was compared with, has always lived with other chimpanzees and does not prefer the company of humans. The roots of Natasha’s prodigious performance remain a mystery.
What Call’s study does reveal is the type of skill that can turn one chimp into a genius. Natasha’s overall performance on physical tasks was within the norm, but she aced every single test of her social intelligence, such as learning from others – a very human characteristic.
Evidence is growing that social skills like communicating and learning are what really set us apart from chimps. of the University of St Andrews, UK, recently demonstrated this in a comparison between human children and chimpanzees. Both were presented with a box with three locked chambers, each containing rewards and opening in a different way. Participants had to open the chambers in the correct order to get the rewards. The children used social skills to crack the problem: they showed each other how they had solved parts of the problem, for instance, and shared the rewards. Chimps tackled the box alone, and failed (Science, ).
Besides defining what can make a chimp particularly clever, Call’s analysis also hints at a key difference between chimpanzee and human intelligence. In human IQ tests, different forms of intelligence like language and spatial reasoning often correlate: individuals that are good at one type of task are generally good at the other. This has led researchers to believe that humans have a “general intelligence” that plays a role in all our reasoning.
Call’s chimps showed no sign of such general intelligence. Being good at physical tasks did not mean they were good at social ones. Such “fracturing” was particularly evident in tests of their social intelligence. In humans, different social skills like communication and learning from others correlate strongly – they come as a package. Bar Natasha, Call saw no sign of this in chimps. This could be a key difference between humans and chimps, he says.
“The apes have these social cognitive skills, but they may not have a way to bundle them together,” he says, which limits what they can achieve. By contrast, even 2-year-old human children have the full set of social skills. That, says Call, may be what gives us the edge over our closest ape cousins.
“The apes have types of social cognitive skills, but they may not have a way to bundle them together”
Animal Einsteins
Explorations of animal psychology often identify talented individuals, usually living in captivity, that can do something unusually clever like use a tool. This frequently leads to statements about the smarts of the entire species, on the assumption that if one dog/chimp/bear can use a tool, every other individual in the species can too.
The poster child for this phenomenon is Kanzi the bonobo. Raised in captivity, Kanzi learned sign language while watching trainers try, and fail, to teach his mother. He also makes noises that seem to correspond to the concepts “banana”, “grapes”, “juice” and “yes”. And if that were not enough, he can make simple stone tools too.
Other animals have achieved similar feats. Betty the crow astonished her keepers when she made a hook by bending a piece of wire: a form of toolmaking even chimps cannot manage.
Alex the parrot (pictured), owned by psychologist until his death in 2007, was another great animal prodigy. Alex had a vocabulary of about 150 words, and Pepperberg claims he understood the concepts behind them. He could also count to 6. Preliminary experiments even suggested that he could add two or three numbers together, but he died before that could be verified ().
This sort of thing cannot tell us much about a species’ abilities, because the animals have been hothoused to ensure they do well, says . If we really want to compare toolmaking in crows and humans, it is not enough to know that one crow can make tools. We need to know how many crows can do it, and how many humans, and whether these talented individuals fare better or worse than their less handy fellows.
Why be smart?
We have long struggled to explain how intelligence evolved.
One theory is that social groups, with their constantly shifting allegiances, select for smarter animals. Animals that live in bigger groups tend to have bigger brains, for example. Additionally, intelligence may be favoured when food is scarce. Black-capped chickadees that are descended from birds that lived in tough environments are better at solving problems than neighbours from mild environments (). They also and .
The trouble is, we don’t know if smart animals live longer than dim ones, or produce more offspring. “Nobody tests the idea that it’s supposedly good to be clever,” says .
Cole is doing just that in wild great tits (). Each one is briefly captured, tagged, and given a simple problem-solving task. It is shown a transparent vertical tube, inside which is a shelf with food on it. The bird must pull a lever to collapse the shelf and release the food. Some do this better than others.
To see how useful smarts are in a natural setting, Cole offers the same birds conventional feeders in the wintertime, on their natural territory. The feeders mimic stores of food that would be naturally available – a seed-laden tree, for instance. Birds that are good at solving problems often get muscled aside by less innovative ones, and obtain less food ().
Despite that, Cole’s early findings suggest brainy and brawny birds survive equally long, and that problem-solvers have more offspring. If that is confirmed, we may finally have a case study of natural selection favouring intelligence. The work was presented at a meeting of the in St Andrews, UK, in August last year.
