All mice are afraid of cats except genetically modified one that Japanese scientists say shows no fear and reveals new traits of mammal behavior.
Scientists at Tokyo University say they have used genetic engineering to successfully switch off a mouse's instinct to cower at the smell or presence of cats - showing that fear is genetically hardwired and not learned through experience, as commonly believed, the AP reports.
"Mice are naturally terrified of cats and usually panic or flee at the smell of one," research team leader Ko Kobayakawa said. "But mice with certain nasal cells removed through genetic engineering didn't display any fear."
"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 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 magazine Nature last month, should help researchers shed further light on how the brain processes information about the outside world.