The unwary purchaser: consumer psychology and the regulation of commerce in America.

Starting in the 1870s, American jurists deciding cases of trademark infringement began advancing arguments that the ordinary purchaser was an unwary one, easily deceived by imitations. Embedded within their legal decisions was a vision of the typical consumers' habitual behavior and cognitive ability. In response to legal critics who argued that the presumed psychology of the consumer was unevenly deployed, applied psychologists developed laboratory-based experiments and scales for determining the likelihood that the "average" purchaser would be confused.