Gaydar

Fruit Machines were actual gaydar devices built to detect gays in the Canadian Civil Service from 1950-1973. ]] Gaydar (a portmanteau of gay and radar) is the intuitive ability to determine whether another person is gay (homosexual), or straight (heterosexual). The function of "gaydar" relies on non-verbal sensory information and intuitions. These include the sensitivity to social behavior and mannerisms: for example; a sensitivity to flamboyant or overt rejection of traditional gender roles (including occupation and grooming habits).

The idea of gaydar is complicated by gay men not acting in a stereotypical fashion and also by metrosexual men who have a heightened aesthetic sense, regardless of sexuality and exhibit a lifestyle, spending habits and concern for personal appearance traditionally likened to those stereotypes of a fashionable, urban, gay man.

Scientific research
A study by the Philadelphia's Monell Chemical Senses Center, published in the Journal of Psychological Science found that "gay men were found to be particularly good at detecting the musk of other gay men".

William Lee Adams, an undergraduate at Harvard, replicated earlier work by his advisor, Dr. Nalini Ambady who is now at Tufts University. Ambady's original study published in 1999 showed that homosexuals are better at correctly identifying sexual orientation than heterosexuals from silent videos and photographs. Adams' research, started in 2004, focused exclusively on the face, the focal point of most social interaction. This finding was elaborated by Ron Smyth and colleagues in 2003.

Criticism
Some feel the idea of "gaydar" has a negative effect on the perception of sexual orientation because it typifies and thus restricts the individuality of those who are detected by the gaydar.

Satire
The news organization The Onion satirizes claims to scientific discovery in the article "I Can Instantly Tell Whether Someone Is African-American With My Amazing 'Blackdar'".

Gaydar in popular culture
Popular cultural references to having a gaydar skill:
 * In the Ellen episode "The Puppy Episode" (originally broadcast April, 1997), Ellen DeGeneres' character learns the concept of gaydar as part of her coming out process. She then explains it to her friends, "I must be giving off one of those vibes again. That's what we do...we give off vibrations and then we pick up the vibrations from our gaydar...so I've heard."
 * In The L Word season one episode "Let's Do It", Dana acknowledges her lack of gaydar after admitting to Alice and Shane she is unable to read the signals from people around her.
 * In Buffy the Vampire Slayer, after Kennedy asks her how long she's enjoyed sleeping with women, Willow responds, "Hey! And what, you think you have some sort of special "lesbidar" or something?" to which Kennedy replies, "Okay, you know there's a better word for that, right?"
 * In the show Gay, Straight or Taken?, a single female contestant dates three guys: one is gay, one is straight and the third has a girlfriend. Her goal is to identify the straight guy who is single in order to win a vacation with him.  To do so, she must use her "gaydar".
 * Saturday Night Live had a recurring sketch about a woman without gaydar played by Rachel Dratch.
 * In the Australian version of Playing It Straight, the dog on the ranch was named "Gaydar".
 * In a TV series called Boy Meets Boy where a gay man meets and chooses a mate from a group of 15 potential male suitors that included both gay and straight men.

Other references to a purported gaydar device:
 * In the Futurama episode "Love's Labors Lost in Space", Bender has what he claims is a literal gaydar - that is, an electronic device that detects homosexuality. The device characterizes nearly every man it evaluates as gay.
 * In The Office (US) episode "Gay Witch Hunt" Jim tells Michael and Dwight that The Sharper Image sells a gaydar device. Jim later sends a modified metal detector to Dwight, who believes it to be a genuine gaydar device.  He becomes concerned when his belt buckle sets it off, thinking it is indicating that he is gay.
 * A segment on The Daily Show shows a man from England named David Eliot who created a gaydar pager device to send vibrations to others carrying the same device. Another episode focusing on gay marriage in Massachusetts uses a fictional gay detection device called a "Homometer" that provides feedback by emitting loud gay mannerisms.
 * On an episode of Saturday Night Live in May 2008, then-presumptive Republican presidential nominee John McCain poked fun at his fiscal conservatism by satirically opposing federal funding for a "Gaydar-jamming" device.