extraction We used the Free Video to JPEG Converter (v. 5.0.6. build 221)software to reconfigure the video as individual frames (25 fps).When viewing the recorded sessions, we used the ethograms pro-vided by Bekoff (1972, 1974), Horowitz (2009) and Ward et al.(2008). Playful interactions varied from rough-and-tumble play to the chasing of one dog by the other. In the latter case, weused the descriptions of canine body language by Abrantes (2005)and Handelman (2008) to distinguish between play and avoidance behavior.