SNIFFING OUT THREATS: Researchers at Northwestern University discovered that our sense of smell can sharpen when something bad happens. It might explain how our senses can help us avoid danger.

THE STUDY: Researchers gave volunteers mild electric shocks while they smelled an odd chemical. In later smell tests, the volunteers' ability to pick out the odd odor was greatly improved.

PHYSICAL CHANGES: MRI scans showed changes in how the brain's main olfactory region stored the odor information, essentially better imprinting the shock-linked scent so it could be distinguished more quickly from a similar odor.

Copyright 2008 The Associated Press.