How rotten eggs could help smokers kick the butt

A new study has revealed that certain kinds of conditioning applied during sleep could induce us to change our behavior.

The researchers exposed smokers to pairs of smells - cigarettes together with rotten eggs or fish - as the subjects slept, and then asked them to record how many cigarettes they smoked in the following week.

Dr. Anat Arzi had previously shown that associative conditioning - Pavlovian-type learning in which the brain is trained to subconsciously associate one stimulus with another - could occur during sleep if odors were used as the unconditioned stimulus.

It was found that though the volunteers did not remember the odors they smelled in the night, their sniffing gave them away: The next morning they reacted unconsciously to tones that had been paired with bad smells by taking short, shallow breaths.

At certain stages of sleep, they were exposed to paired smells - cigarettes and a foul odor - one right after the other, repeatedly throughout the night. Although they did not remember smelling the odors the next morning, the subjects reported smoking less over the course of the next week. In contrast, subjects who were exposed to the paired smells when awake did not smoke less afterward, nor did sleepers who were exposed to cigarette smells and the two aversive smells unpaired, at random times.

The study was published in The Journal of Neuroscience.