Genetically Engineered Mice Don't Fear Cats

A genetically modified mouse sniffs a cat in Tokyo in an undated photo.

Using genetic engineering, scientists at the University of Tokyo say they have successfully switched off the rodents' instinct to cower at the smell or presence of cats. The researchers say their experiment shows that fear is genetically hardwired and not leaned through experience, as commonly believed.

Photograph courtesy Ko and Reiko Kobayakawa, University of Tokyo Department of Biophysics and Biochemistry Graduate School of Science, HO/AP

Kaori Hitomi in Tokyo
Associated Press
December 13, 2007

The age-old animosity between cats and mice could be a thing of the past.

New genetically engineered mice show no fear of cats, according to the Japanese scientists who created the rodents. The modified mice may also shed new light on mammal behavior.

Scientists at the University of Tokyo say they have used genetic engineering to successfully switch off a mouse's instinct to cower at the smell or presence of cats—evidence that fear may be genetically hardwired and not learned through experience, as commonly believed.

"Mice are naturally terrified of cats and usually panic or flee at the smell of one. But mice with certain nasal cells removed through genetic engineering didn't display any fear," research leader Ko Kobayakawa said.

"The mice approached the cat, even snuggled up to it and played with it," Kobayakawa said.

"The discovery that fear is genetically determined and not learned after birth is very interesting and goes against what was previously thought."

The findings suggest that the human aversion to dangerous smells like that of rotten food, for example, could also be genetically predetermined, he said.

Kobayakawa said his findings, published in the science journal Nature last month, should help researchers shed further light on how the brain processes information about the outside world.

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