Japan Scientists Develop Fearless Mice

In this undated photo released by Tokyo University's Department of Biophysics and Biochemistry Graduate School of Science, a genetically modified mouse approaches a cat in Tokyo. Using genetic engineering, scientists at Tokyo University say they have successfully switched off the rodents' instinct to cower at the smell or presence of cats, showing that fear is genetically hardwired and not leaned through experience, as commonly believed. (AP Photo/Ko and Reiko Kobayakawa, Tokyo University Department of Biophysics and Biochemistry Graduate School of Science)

(AP) -- Cat and mouse may never be the same. Japanese scientists say they've used genetic engineering to create mice that show no fear of felines, a development that may shed new light on mammal behavior and the nature of fear itself.