Let me tell you the story of how I learned my first curse (and hence sexual) sign.
I was 5 years old, and as part of the local deaf program, I was on what some call "the short bus." It shuttled children who lived outside the regular bus routes to and from school. There were several other deaf kids on board, their ages ranging from 4 to 9.
You can imagine the things that went on during that bus ride.
One day, an older deaf boy beckoned to me and said, "Hey, want to learn a new word?"
No 5-year-old girl could pass that up. I went over and sat by him, eager to learn a new word.
He proceeded to show me a sign that could be classified as "cranking a bird." On the side of his fist, he made a motion as if he was turning a crankshaft and presto, his middle finger went up.
I was instantly entranced. I spent the remainder of the bus ride practicing this smooth move. The boy told me that I could use to say goodbye. When we reached my stop, I flounced over to the bus driver and showed him the new, snazzy sign.
His face got a little red and I'd imagine that he gasped, but I'm not sure, since I—of course—couldn't hear him. When my mother came to the door to retrieve me, he told her what I had done and how she should teach me never to do such a filthy thing again. My mother proceeded to tell me that it was a sign I should never use.
Of course, being told that I couldn't sign something made me curious about what it meant. So, I went and asked some of my older friends. (One benefit of deaf education is that you're around a lot of older and younger kids.) One of my best friends, who was a girl two years older than I was, proceeded to tell me about sex and re-enacted it using dolls. (Later, I learned that the positions were a bit off, but they weren't bad, considering our relative inexperience.)
That, ladies and gentlemen, is the story of how I learned what the f-word meant. I was definitely a bit too young, but I turned out OK.
Sexual content in American Sign Language
As others have mentioned, people learn sexual signs and profanity from one another, and trust me, there are plenty. If you really want to learn sexual signs, I'd suggest that you hang out with deaf teenagers, since they are well-versed in the subject.
All that being said, I want to explain a bit about how sexual signs work in ASL and why it's a bit different than in a spoken language.
Hand positions as visual representation are very important parts of ASL. You can assign concepts or objects to particular hand shapes, motions, or even just spatial spaces. For example, if I wanted to say something like, "She crossed her legs," I wouldn't have to sign each word. I'd just use two bent index fingers and cross them in a visual representation of crossed legs. This phenomenon is more formally called "spatial metaphors" and is heavily used in ASL poetry.
Think for a moment about that and about sexual acts. It's very easy to assign sexual parts to a hand shape. Most commonly, ASL signers use either a pinky or an extended index finger to indicate penis but occasionally use an entire forearm. (Yeah, they're probably overestimating their prowess there.) I'll leave it to you to figure out the visual representations for vagina.
Moreover, there are more and less explicit ways to refer to sexual acts. I wouldn't use a certain sign for a particularly racy sex position if there were kids around. I might go as far as to just finger spell it. The sign that you'd use for intercourse would be different in a sex-ed class compared to a conversation with your friend about your latest hot affair. Context matters, just like in spoken language.
The flexibility that ASL provides in terms of illustrating sexual acts, positions, and preferences can give rise to pretty amusing things. One of my friends came up with an ASL poem that used each letter of the alphabet to represent a sex act. It was quite stunning to watch, in a good way.
Deaf people have the same sexual desires and thoughts as anyone else, and they definitely find ways to express them.
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