Dr. David Burliner, who worked at Utah University at that time, collected skin cells that had come off from the cast of a skier who broke his limbs to study what human a human cell was composed of. During his study, he noticed something unusual about people working in his laboratory.
When the bottle containing extracts from the skier’s skin cells was left open, some of his colleagues in the lab – who were not the most cheerful people – laughed more often than usual, which caused a friendlier atmosphere to the lab. The doctor’s curiosity was further aroused when one of his female colleagues who were usually clerical and hardly spoke even asked other colleagues for play cards during a lunch time.
When the cap was put back on the bottle, the behaviors of these researchers went back to usual. They were no longer cheerful, but sullen and standoffish as usual.
This led to further researches on human pheromones, and researchers finally discovered that human’s vomeronasal organ, a small depressed area located on the tip of the nose – which was thought by researchers in those days to be a degenerated organ and unnecessary to humans – perceives pheromones and stimulates the hypothalamus of human brain to respond with various behaviors.
Pheromones are not perceived by the brain as "smells". They are unconsciously received by the brain, directly stimulating it to secrete hormones to elicit a response. It is said that they stimulate our subconscious mind, a much deeper level of the mind we are usually aware of.
Normally, a smell is sensed by the olfactory nerve in the mucous membrane of the nasal cavity, which sends a signal to the brain to judge whether the smell is “pleasant or not.” In contrast, a pheromone is received by the vomeronasal organ, a small depressed area located at the tip of the nose and sends a signal to the hypothalamus, which is responsible for sexual desire and hormone secretion.
Perceived not by the sense of smell but by the so-called "sixth sense", pheromones stimulate the “instinctive part” of our nature, or the most primitive part of the brain, beyond our human intelligence and rationale.
It is known that pheromones are sensed and perceived by the brain differently from smells, because they are almost odorless and can be perceived by the brain even in an extremely small amount (a trillionth of 1 gram).