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schematic spiders

Babies 5 months old spent more time staring at a realistic schematic of a spider (left) than at slightly (center) and highly (right) scrambled versions.

Why Miss Muffett skedaddled

Infants may be hard-wired to respond to spiders

By Deane Morrison

April 16, 2008

When Peter Jackson was sketching out the Lord of the Rings characters, he wanted the spiderlike monster Shelob to make the audience's skin crawl the same as real spiders had done for him as a child. In a way it was an easy task, because plenty of people harbor a lifelong fear of spiders, even though most are harmless. It's as though we're born with a predisposition to develop arachnophobia. Actually, that may not be far from the truth. A study by University psychology graduate student Jaime Derringer and a colleague suggests that the human brain has evolved to single out spiders for special attention. Working with 5-month-old infants, Derringer found evidence that while we're not born afraid of spiders, evolution has given us the tools to quickly learn such fear. She performed the work under the direction of David Rakison, an associate professor of psychology at Carnegie-Mellon University, where she received her undergraduate degree. The two recently published the study in the journal Cognition. In brief, the infants in the study seemed to have a brain "template" for spiders that draws their attention to the arachnids the first time they encounter one. They aren't afraid of them, though. Children most likely learn to fear spiders later, after watching adults or older kids respond that way, Derringer says. "These infants were not afraid of spiders," she explains. "They had had no traumatic spider experiences. They were just starting to get around and hadn't discovered any spiders on their own." The brain template that predisposes babies to respond to spiders may be activated by the age of 5 months because that's when infants are about to start crawling and exploring and maybe encountering spiders, she adds.

"... Women are four times more likely to have phobias for these stimuli than men. Women in the evolutionary past would have been gathering and looking out for infants, and so may have had more need to be vigilant."

In the experiments, Derringer presented infants with images on a computer screen and noted how long each held their attention. They stared longer at a combination of lines and shapes when they closely resembled a spider than when they resembled a spider either slightly or not at all. (See photo above). But when babies who had been shown pictures of real spiders were presented with these images, they showed the least interest in the most realistic spider shape. This, say the researchers, is what one would expect if babies have an inborn template that helps them learn about spiders in their environment. That is, once they have become habituated to images of real spiders, the realistic schematic should be familiar--and thus less interesting--to them. "They're categorizing the schematic spider as the same as [real spiders] in the photos," Derringer explains. "We showed them photos [of real spiders] until they became bored with them. Then we showed the stick figures, and they weren't as interested." She also found that infants were not "fooled" by schematic spiders that had rectangular, instead of curved, bodies and legs. And they showed no evidence of having a brain template for a nonthreatening organism--namely, a flower. This work builds on studies by a variety of researchers working with primates and other animals, the researchers note. Those studies pointed to an innate ability to respond to predators. Rakison is now repeating the spider study with images of snakes, since the idea is that the brain template primes infants to quickly learn that spiders and snakes should be avoided." So far, says Rakison, the data look promising. And who is especially quick to associate spiders and snakes with danger? "We're finding that girls learn pairing much more quickly than boys," Rakison says. "Also, women are four times more likely to have phobias for these stimuli than men. Women in the evolutionary past would have been gathering and looking out for infants, and so may have had more need to be vigilant." Rakison knows of no similar research being done elsewhere on the underpinnings of fear. It is quite possible, say he and Derringer, that infants are born with templates for many kinds of potential dangers. They may even have one "for male humans that facilitates the anxiety toward men but not women that appears around 7 months of age." Curious about spiders? Read about some common ones.