Abstract

Many “higher” animals are commonly assumed to distinguish between individual humans. This belief
is based largely on anecdotal reports; in reality, there is little empirical evidence to support human
recognition in nonhuman species. Wereport that laboratory rats consistently chose a familiar human
over an unfamiliar human following fourteen and five IO-min exposures and even following a single
IO-min exposure. Furthermore, this preference was retained in the absence of additional contact for at
least 5 months. These results confirm that laboratory rats can tell individual humans apart, a prerequisite
for associating them with hedonic events. Such human-based conditioning, described by
Pavlov and by Gantt, Newton, Royer,and Stephens (1966),may have important implications for animal
research in a variety of settings.