To boost mood or stir up old memories, people can use their nose. Scent can even drive a person to romantic distraction—for some, just a whiff of a partner's pajamas can do the trick. The nose can even suss out complex mechanisms like sexual compatibility. The well-known "dirty T-shirt" experiments are evidence of how people are drawn to certain smells and odors. In one such study, researchers had male subjects don new T-shirts for two consecutive nights. Female study participants later sniffed each shirt and deemed which ones had the most attractive scent. They preferred the shirts worn by men who were more immunologically dissimilar to themselves. This makes biological sense, as pairing dissimilar immune systems can mean healthier offspring. In fact, some studies indicate that dissimilar MHC genes, which recognize foreign substances, result in lower rates of early miscarriages.
The Power of Scents
The Complex Role of Scents
The human body has more than 100 immune system genes known as the MHC, or major histocompatibility complex; these genes help our immune system suss out unwanted pathogens. The MHC determines, for example, whether an organ donor is compatible to the patient in need of a transplant. It also determines histocompatibility, influencing people in their mating choices. In MHC experiments, women are generally more discriminate and fussy about smells and odors, possibly because they are more invested in the results of reproduction, bearing children and caring for them. Some researchers contend that smell may be the most important, albeit the most subtle, factor in physical attraction.