This perceptual shorthand of drug dealers processes one of two types of deception clues in determining whether buyers are undercover: trend discontinuity and interpersonal illegitimacy. Trend discontinuity, which is associated with police informants, results from situations in which familiar customers suddenly introduce unfamiliar persons who want to buy drugs or suddenly and significantly increase quantities they themselves wish to purchase. The interpersonal illegitimacy is associated with undercover agents and stems from situations in which unfamiliar buyers emit certain physical and verbal "vibes" believed to be indicative of covert law enforcement personnel. The dealers interviewed did not fear getting caught by undercover drug agents as they were confident that the perceptual shorthand would filter them out. Some dealers did get caught, but these dealers could draw from the "experiential effects" and subsequently deal with reduced fear of apprehension. 5 notes and 52 references