May 8, 2006 -- Lesbian women and heterosexual women respond differently to the scent of human pheromones, a new study shows.
Pheromones are chemicals known to drive one or more behavioral responses in animals, including sexual behavior.
The new study comes from Ivanka Savic, MD, PhD, and colleagues. They work at the Karolinska Institute in Stockholm, Sweden.
The researchers studied brain scans of lesbian women, heterosexual women, and heterosexual men while those people smelled scents including two potential human pheromones.
Brain scans taken while smelling those pheromones were more similar for lesbian women and heterosexual men than for lesbian women and heterosexual women, the researchers report. Their study appears in the online early edition of Proceedings of the National Academy of Sciences.
Last year, Savic's team published a study showing that homosexual men and heterosexual women had similar brain activity patterns when smelling those same human pheromone candidates.
Sexual preference may sway the brain's response to the pheromones, the researchers note.
Savic's team studied two candidate compounds for human pheromones. Those potential pheromones are called "AND" and "EST."
AND is found in human sweat. The concentration of AND in men's sweat is about 10 times greater than in women's sweat, Savic's team notes.
The researchers describe EST as "an estrogen-like steroid."
Savic's latest study included 12 heterosexual men, 12 lesbian women, and 12 heterosexual women. All were healthy and not taking medication.
The lesbian women had normal hormonal levels. Regardless of sexual orientation, the women were studied at the same point in their menstrual cycle.
Participants were given glass bottles containing scents including AND, EST, lavender oil, or cedar oil. Each bottle only contained one scent.
Meanwhile, the researchers scanned participants' brains with magnetic resonance imaging (MRI) and positron emission tomography (PET) technology. Afterward, participants rated the scents for pleasantness, irritability, intensity, and familiarity.
Lesbian and heterosexual women showed different patterns of brain activity while sniffing AND and EST, the study shows.
While smelling AND and EST, the brain activity pattern for lesbian women was closer to that of heterosexual men than heterosexual women, Savic and colleagues note.
However, the previously reported similarities between brain activity for heterosexual women and homosexual men while sniffing the pheromones were stronger than those between lesbian women and heterosexual men.
The pheromones didn't necessarily have a sexy smell. "None of our subjects reported sexual arousal" while whiffing any of the scents, the researchers write.