Fragrance, also known as perfume or cologne, is a liquid mixture that emits a pleasant odor when rubbed on the skin. It is composed of fragrant essential oils extracted from plants or synthetic aromatic chemicals. It is usually combined with fixatives, which slow the evaporation of the fragrance and increase its longevity, and a solvent, a chemical that dissolves and contains the fragrance ingredients. Historically, perfume was created from plant materials, but modern perfumes are mostly synthesized in laboratories. Fragrances are widely used in a variety of personal care products such as soaps, deodorants, shampoos, lotions and body sprays. They are also commonly used in household cleaning and air freshening products. Some fragrances may contain hormone-disrupting and allergenic chemicals.
Despite its popularity, little empirical research has been conducted on the role of fragrance in human behavior. While anecdotes and speculation abound, several observations suggest that perfume is an intrinsically rewarding stimulus. For example, perfume is created for and worn for pleasure more than any other function, and its use evokes positive emotions. Moreover, the hedonistic pleasure derived from smelling a favorite perfume seems to trigger the reward centers of the brain, including the orbitofrontal cortex (OFC) and amygdala.
In addition to its inherent rewards, perfume may also act as a socially-contextually determined reinforcer. For example, the scent of perfume may help a woman seduce a man or mask the presence of an unpleasant body odor that would otherwise signal genetic incompatibility (Herz and Cahill 1997; Herz and Inzlicht 2002).
It is important to note, however, that the context in which a smell is perceived strongly influences its connotation and denotation. For example, a smell of sweat and alcohol might carry negative connotations for some people, while others find it invigorating. The same is true of perfume; a perfume with a floral scent may have a more feminine connotation, while a woody fragrance may elicit masculine one.
Two studies of female job interviewees found that wearing perfume caused men to devalue their ability for a job, but this result is not universally applicable. The first study compared women who did and did not wear the popular perfume Jontue to their male counterparts in a professional setting. The second experiment analyzed the effects of different olfactory stimuli in a laboratory setting. Both experiments found that men discounted the ability of female confederate job candidates who wore perfume, but this effect was not present in a field setting.
In the future, neuroscientific research on fragnance could be useful in understanding how these hedonistic and socially-contextually determined stimuli reinforce human behavior. The OFC and amygdala are involved in both reward and olfactory processing, and the dopaminergic pathway innervates both the OFC and amygdala. The degree to which the experience of smelling a particular perfume activates this circuit is an intriguing question that awaits innovative neuroscience and reward research.