When we talk about the argot of drug users, we mean their vocabulary or the collection of slang words and phrases used by one drug user to communicate with another—often to the exclusion of non-users. In some instances, argot extends to the intonation orpitch used to speak words and phrases.

Argot fascinates sociologists, anthropologists, and others who study human behavior because the use of argot is an example of learned behavior that helps identify members of one social group as opposed to another, Argot also marks off the boundaries of group membership: those of the in-group use argot with ease, while outsiders use argot ineptly ornot at all.

In one study, we showed more than 2,000 drug users in Baltimore, Maryland, a photograph of someone injecting a drug into a vein, and we asked "What do you call this?" The vast majority, well over 50 percent, said that it...