Video 1. Showing experimental protocol for the establishment of empathy for pain model in laboratory animals.

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During Days 1-3, environmental and manipulating adaptation to the experimental environment and manual handling by the experimenters. On Day 4, the baseline values of PWMT in both hind paws of a naive CO rat were first measured and determined using a set of von Frey monofilaments, followed by a VCR of 30-min PDSI between a naïve CO and a familiar conspecific (CD) in pain (for detailed behavioral expressions during 30 min PDSI also see Video 2 that was finally succeeded by last measurement of PWMT for determining whether social pain contagion occurred in the naive CO rats.