In Experiment 1, we investigated whether rats help their cagemates in a distress situation. We created the distress
situation by soaking a rat in water. In addition, we carried out several control tests to confirm the importance of the
existence of the distressed other individual for occurrence of the helping behavior. To confirm the experimental operation, the rats were tested for preferences regarding water. Finally, we examined the effects of prior experience of exposure to the distress situation. If the helping behavior is motivated by empathy, such a prior experience should lead to the rat engaging in the helping behavior more quickly