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Humans not just “big-brained apes,” researcher says
Aug. 22, 2007
Courtesy PNAS
and World Science staff
Updated Aug. 24
In discussions on animal intelligence, it’s fashionable to play up animals’ smarts and their similarities to humans. And many studies provide fodder for such thinking.
But a new study, reassessing much past research, offers a different perspective: it argues that key human-animal differences are often overlooked. Humans are more than just “big-brained apes,” as Charles Darwin called them in 1871, wrote the author, psychologist David Premack of the University of Pennsylvania in Philadelphia, Penn.
Many studies have examined ape intelligence. In this image, the chimp "Jessie" removes a blindfold from a trainer who also has the key to a box containing a banana. Researchers say this shows Jessie grasps the concept of "seeing": she realizes that if she takes off the blindfold, the trainer can open the box. While such studies often play up apes' similarities to humans, a psychologist says they often overlook the great differences: for instance, animal actions usually center on narrow objectives like food or sex. (Image courtesy Proceedings of the National Academy of Sciences)
In trying to change such conceptions, Premack is swimming against a tide of research that has found sometimes surprising cognitive abilities in animals, capacities once thought unique to humans.
A study published last July, for instance, found that even some rodents can remember the “what, where and when” of events in their lives, an ability sometimes cited as key to consciousness. And findings made public just this week suggested rhesus monkeys use “baby talk” with infants, though surprisingly, not their own.
Premack didn’t challenge the findings of past studies. But he argued that they often focus on animal-human similarities—striking us repeatedly with examples of how animals are “so like us”—while glossing over the vast realms of activity where they’re really quite unlike us. That leads to the false idea that animals have human-like abilities, he said.
Further confusion has arisen because human brains do have similarities in structure to other mammals’, added Premack, whose paper appeared in this week’s early online edition of the research journal Proceedings of the National Academy of Sciences. For such reasons, most neuroscientists agreed with Darwin until recently.
Only since the late 1990s has research challenged that notion, by revealing microscopic features unique to human brains, Premack wrote. These studies have found “enhanced wiring, and forms of connectivity among nerve cells not found in any animal.”
One such finding, he added, involved a newfound type of neuron, or brain cell, that’s far more numerous and larger in humans than in any of their ape relatives. Called von Economo neurons, these cells are particularly prevalent in brain regions dealing with social emotions such as empathy, guilt and embarrassment, Premack wrote.
In a critical analysis of past literature, Premack examined claims of similarity between animals and humans in several different areas, including teaching, deception, memory, and language. In all cases, he argued, the similarities are small and the differences large.
A major difference is that animal behaviors appear to be mainly adaptations focused on a single goal such as food-seeking, he wrote, whereas human behaviors have an infinite number of goals. Such disparities are consistent with the observed differences in brain structure; the challenge is to understand the function of these cellular-level differences, he wrote.
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