In the old Family Feud game show, contestants battle to fill in the blank with the most popular answers for questions like "Name a famous Julia" or "Name something you do on the beach". The skill of the game is to figure out what other people think and are likely to say; this is a hard game to do well at if you are not deeply familiar with the idiosyncrasies of the culture and the language. Native speakers of a language have a lot of tacit knowledge about which words tend to go together and which clash. If we play a game where I say a word and you say the first word that comes to your mind, I can predict with some degree of accuracy what you'll say. (Quick -- I say "doctor" -- what do you say?) This tacit knowledge is based partly on which words we've heard and read together in the past. Don't believe me? Two computational linguistics researchers named Justeson and Katz did a study back in the early 90's that showed that by counting how often pairs of words occurred close together in a stretch of text, they could predict which words would be considered the opposites -- or antonyms -- of a given word, and which would not. Are antonyms obvious? What is the opposite of "light"? Most people would say "dark", but why not "dim"? What's the opposite of "big"? Most people would say "small", but why not "little"? What is the opposite of "rough"? Why is it "smooth" rather than "even"? The answer is that we as native speakers have been exposed to these words co-occurring in sentences day after day, week after week, month after month, and year after year, till we mentally "hear" these as being the correct antonyms and don't ever consider the alternatives. Initially, I found it counter-intuitive that antonyms co-occur. You would think that they talk about things that are opposite one another, so their contexts shouldn't overlap. But this is where the linguistic aspect comes in. Antonyms are often used to contrast concepts, and so often appear close together in text. Thus you might say "She's not happy, she's sad" or "Do you want the big one or the little one?" We even hear antonyms together in common phrases and clichés, such as "it's like night and day". In summary, although there are many concepts that represent opposite meanings, only certain words are conventionally used to express these opposites, thus achieving the status of antonyms. People learn which ones sound right by frequent exposure to the words within text and spoken language. If you don't know the language well, you use the wrong adjective and you lose at Family Feud. And that's the long and the short of it.

(Did you say "nurse" above? Of course you did!)

-Marti Hearst

*Editor's Note: Marti is a professor at Berkeley in the very cool School of Information and a consultant at Powerset. All opinions expressed are more or less hers. When she's inspired by a cool feature of language, she'll blog it here.*