It takes a nose to know danger!

New research from the U.S. says the nose is a quick learner and can sniff out danger.

According to researchers from Northwestern University's Feinberg School of Medicine, all it takes is one bad experience and the nose remembers the danger.

As every nose is subjected to hundreds of thousands of scents every day, some of which are almost identical, it is intriguing how we learn to distinguish the critical ones apart from each other.

Lead author of the study Dr. Wen Li, says it is evolutionary and a single negative experience linked to an odor rapidly teaches us to identify the odor and discriminate it from similar ones.

Dr. Li says this helps us to have a very sensitive ability to detect something that is important to our survival from an plethora of environmental information and warns us that its dangerous and attention to it must be paid.

For the study, subjects were exposed to a pair of grassy smells which were nearly identical in their chemical makeup and perceptually indistinguishable; they then received a mild electrical shock when they were exposed to one scent, but not when they were exposed to the other similar one.

The subjects only learned to discriminate between the two similar smells after being shocked and the researchers say this illustrates the tremendous power of the human sense of smell to learn from emotional experience - odors that once were impossible to tell apart became easy to identify when followed by an averse event.

MRI scans, which can measure brain activity, revealed clear differences in a part of the brain called the olfactory cortex before and after the shocks.

The researchers also found specific changes in how odor information is stored in "primitive" olfactory regions of the brain, enhancing perceptual sensitivity for smells that have a high biological relevance.

The study will be published March 28 in the journal Science.