"Something" in the way she smells.

• Position: YOUR LIFE - Romantic attraction

The Beatles' George Harrison wondered in his famous song about the "something" that "attracts me like no other lover." A University at Buffalo (N.Y.) psychologist explains that that "something" actually is several physical elements that--if they occur in a certain order, at the right time and in the right place--can result in true love.

"There are several types of chemistry required in romantic relationships," observes Mark B. Kristal, professor of psychology. "It seems like a variety of different neurochemical processes and external stimuli have to click in the right complex and the right sequence for someone to fall in love."

First, there is smell, made up of learned or cultural preferences, such as the smell of a dozen long-stemmed red roses. "Smell forms part of the framework that conforms to cultural attractiveness standards; for example, smelling like a strawberry instead of mildew."

Next, there are pheromones, which are more mysterious to humans. "Pheromones are unlearned, and perhaps unsmellable, signals that enter the brain through the olfactory system. They can function in sex, alarm, territoriality, aggression, and fear," Kristal points out, adding that, while sex attractant pheromones may account for changes in libido, they do not explain why we choose a specific person for a mate.

"In humans, specific mates are more probably chosen on the basis of other sensory cues: visual, regular olfactory, auditory, and tactile cues," Kristal notes. These...