Chicago ? The little electrical shocks that Wen Li gives subjects at her Northwestern University neuroscience lab feel less painful than a bad jolt of static electricity, and more like the mild snap of a rubber band on skin.

But getting just seven of those shocks trained people in a new study to distinguish between extremely similar odors, offering a new and perhaps potent way of changing a person’s power of perception.

Psychologists have used the basic conditioning technique for decades to alter the behavior of people and animals. But experts said the Northwestern study went further by actually modifying how the brain processes the sensation of smell.

The new report, published in today’s issue of the journal Science, illustrates the power of emotions like fear to shape how we learn and even perceive the world, said Dana Small, a neuroscientist who studies odor and taste at the John B. Pierce Laboratory in New Haven, Conn.

One possible implication of the work could be new insights into phobias and conditions like post-traumatic stress disorder, which can increase a person’s sensory sensitivity. The group’s conditioning regimen could even lead to new therapies to alleviate the sensory overload of such patients.