Pellis, S. M., Pellis, V. C., Ham, J. R. et al. 2022. The rough-and-tumble play of rats as a natural behavior suitable for studying the social brain. Frontiers in Behavioral Neuroscience 16, 1033999.

Laboratory rats have been an important model species with which to study the neurobiology of rough-and-tumble play (RTP). RTP in rats involves competition to gain access to the partner’s nape of the neck, which is nuzzled with the snout if contacted (Pellis and Pellis, 1987; Siviy and Panksepp, 2011). A variety of tactics are used to attack and defend the nape, including launching counterattacks following a successful defense. Rats are a particularly good model species for studying RTP, as this behavior not only differs from serious fighting in the ways described above, but also because serious fighting involves attacking other body targets, namely the flanks and rump, which are bitten if contacted (Blanchard et al., 1977; Pellis and Pellis, 1987). Consequently, it can be readily discerned when a playful encounter escalates to serious fighting, as the aggressor switches from attacking the nape to biting the partner’s posterior. Even within members of the same sex and same strain, not all individuals play to the same degree—some rats consistently play more than others. Such individual differences provide an opportunity to refine the search for the neural mechanisms that regulate play. Furthermore, Not all partners are equally attractive as play mates. When rats are tested in groups, in which multiple partners are available, play is not distributed evenly. Studying RTP can be a valuable tool both for basic research on communication and other processes that are involved in regulating social behavior, and for translational research on neurodevelopmental disorders.