They might have opposite preferences when it comes to choosing partners, but gay men and straight women's brains are on similar wavelengths, according to a new research.
Similarly, lesbians and straight men's have similar brains, in some respects, the study adds.
In the study, the scientists found resemblances in the brain's physical structure and size as well as the strength of neural connections among gay people and straight people of the opposite sex.
"[Our] data are more difficult to explain by a specific learned behavior related to ... sexual orientation," National Geographic quoted study leader Ivanka Savic, a neuroscientist at the Karolinska Institute in Stockholm, Sweden, as saying in an email.
Differences both in the brain activity and anatomy were observed in a study involving 90 men and women, including homosexuals and heterosexuals of both genders.
The researchers monitored neural activity in the brain by charting blood flow. The scans were carried out when the volunteers were resting and exposed to no external stimuli.
Researchers focused in particular on the amygdala, an almond-shaped structure inside each brain hemisphere associated with processing and storing emotions.
In homosexuals, brain activity most closely matched that of heterosexuals of the other sex.
Also, homosexual men and straight women showed significantly more neural connections across the two brain hemispheres than heterosexual men did.
The two sides of the brain also changed in symmetry depending on the person's sexual orientation.
To determine brain volume, the research team also compared the left and right cerebral hemispheres using magnetic resonance imaging (MRI) scans and previous research data.
The right hemisphere was found to be slightly larger than the left in heterosexual males and lesbians, whereas those of gay men and straight women were symmetrical.
The latest findings imply that "human sexuality has neurobiological underpinnings," the mechanisms of which are complex and "require humbleness and restraint from quick judgments," Savic said.
The study will be published in the journal Proceedings of the National Academy of Sciences.