It's a blindingly beautiful summer morning, yet I'm indoors sniffing green apples and looking at pictures of faceless naked men. Don't worry, Mom -- it's all in the name of science. The apple scent has been infused into a blue surgical mask slipped over my nose and mouth; the tiny black-and-white photographs show twenty men of differing body types with heads and genitalia blocked out. I'm supposed to gauge their weight, age and attractiveness as part of a preliminary study that checks the effects of odor on weight perception. So far, I only feel vaguely queasy after seeing so many alternately flabby and emaciated bodies -- all while inhaling what seems to be the equivalent of Lysol Country Fresh spray. Still, the research assistant says that while smelling the green apple, traditionally considered a soothing and pleasant aroma, other test-takers have rated the heaviest men to be slightly lighter than their actual weight.This is one of about fifty ongoing experiments at the Smell and Taste Treatment and Research Foundation, a decade-old Michigan Avenue center dealing with everything anyone would want to know about olfaction. And if the above study -- along with foundation's name and mission -- sounds a bit, um, "senseless", then you're not looking at the big picture. Any connection between smell and perception eventually may help physicians map out our brain's circuitry, holding huge medical and psychological potential, possibly developing treatments for afflictions from impotence to migraines. As it is, scientists have already documented the intense effect of smell on our emotional state, memory and behavior."Smell is particularly important in the realm of emotions because it's the quickest way to induce change in mood -- faster than any other sensory modality," says foundation director Dr. Alan Hirsch at his Water Tower office. "When you smell something, you immediately decide whether you like it or don't like it, and then you secondarily cogitate the smell as rose or lilac. It's very different to sight, when you see a picture of a cow or a tree and identify it as such before deciding on how you feel about it."Hirsch straightens his white lab coat and grabs a brain chart to illustrate the key to the link -- aromas first pass through the olfactory lobe, which sits comfortably within the limbic cortex, the core of emotional behavior, memory and sexual drive. That's partly why smell might trigger intense memories: A whiff of a certain perfume, for example, can transport you back thirty years to a visit with grandma while freshly cut grass reminds you of gardening with your father. Vision, hearing and touch, meanwhile, are processed in the brain's other hemisphere. "Evolutionarily it makes sense because smell was important to survival of the species," Hirsch says. "Why do we yawn when we're sleepy? If you yawn, more air goes into your mouth; hence, more air goes through your nose and you're better able to detect a potential predator that'll eat you when you're asleep." He pauses. "Well, that's a theory at least."Several of Hirsch's examples are theories, partly because the reasons behind many of his findings are still murky; research of smell and other senses were ignored in the past. "We're pretty much where opticians were when they first used the E chart years ago," Hirsch says. "It's always been an area that's fallen between specialties."The brain can detect millions of odor molecules, but humans only register about 10,000 of the more important combinations of smells. At Hirsch's office, a cupboard houses little brown bottles filled with a few dozen of those fragrances, such as concentrated cinnamon, popcorn, jasmine, peach, chocolate, even barbecue. The foundation uses artificial bouquets rather than natural ones to achieve more regulated experiments. Studies investigating the effects of odors on exercise, consumer behavior, lying, learning, anxiety and countless other syndromes have netted Hirsch appearances on "20/20," "Dateline," "The Oprah Winfrey Show," "Good Morning America" and "48 Hours."Hirsch garnered the most ink two years ago when he measured the sexual response of twenty-five male medical students by monitoring their blood pressure and penile blood flow. Thinking flowery scents would stimulate the volunteers -- the olfactory bulb at the top of the nose and the brain' s septal nucleus, which powers erections, are connected -- Hirsch bombarded the men with perfumes, using the smell of cinnamon rolls as a control only to find that the baked good triggered the highest arousal levels. He then performed a similar study, exposing another group to thirty scents, from baby powder to grapefruit. Perfume beckoned their private parts at a 3 percent increase of excitement; a lavender/pumpkin pie mix provoked a 40 percent rise."It could have a lot of implications for sexual arousal disorders, but we need to figure out why there was an increase -- maybe medical students are hungry all the time," he says with a laugh. "Other theories are that the odors induced a Pavlovian response, or maybe there are evolutionary links with food smells because ancestors roamed around and congregated mainly around food kills, so that was the place where you had the greatest chance of finding a mate. You could say that love at first sniff is more accurate than love at first sight."Hirsch, who's both a neurologist and psychologist at Rush-Presbyterian-St. Luke's Medical Center and Mercy Hospital, became interested in olfaction while serving his psychiatry residency, when he wondered why several patients couldn't smell. It was only after he launched his research that he figured out the patients' prescribed drugs were knocking out their noses. Still, most of his studies are based on clinical cases culled from the roughly 1,000 patients who visit the foundation every year. The light bulb for his recent book, "Dr. Hirsch's Guide to "Scent"Sational Weight Loss," came from his observation that many of his patients gained weight when their sense of smell was impaired. So he tried the opposite -- giving overweight folks inhalers to sniff whenever they were hungry.Most of his patients are asnomic (people who can't smell), usually because of head trauma. However, their biggest problem isn't reduced taste; rather, Hirsch says they begin to feel socially isolated. "We often don't realize it, but smell is used to have contact with other people," he explains. "People who lose smell become more depressed and anxious." He pauses for a moment. "Of course, they're also more likely to get food poisoning and die in natural gas explosions." And what about taste, the other sense mentioned in the foundation's title? Hirsch makes a slight face. "Ninety percent of taste is really retro-nasal smell rising from the mouth, and people usually confuse taste with flavor. "It's really about smell."