PREFERENCE FOR FAMILIAR HUMANS BY RATS

Many ''higher'' animals are commonly assumed to distinguish between in dividual humans. This belief is based largely on anecdotal reports; in reality, there is little empirical evidence to support human recognit ion in nonhuman species. We report that laboratory rats consistently c hose a familiar human over an unfamiliar human following fourteen and five 10-min exposures and even following a single 10-min exposure. Fur thermore, this preference was retained in the absence of additional co ntact for at least 5 months. These results confirm that laboratory rat s can tell individual humans apart, a prerequisite for associating the m with hedonic events. Such human-based conditioning, described by Pav lov and by Gantt, Newton, Royer, and Stephens (1966), may have importa nt implications for animal research in a variety of settings.