Figure 1. Rats were as motivated to help strangers of the same strain (SD stranger; right) as they were to help cagemates (SD cagemate; left).
In both experimental conditions (diagrammed at top), SD rats were housed with another SD rat. However in the cagemate condition, the cagemate served as the trapped rat (‘a’) whereas in the stranger condition, the trapped rat was a stranger (‘?’) and not the cagemate (‘b’). Across the days of testing, the median latency to door-opening (bottom) decreased for both conditions.