Are chimpanzees "stuck" on their "selves" in video?

Hirata, Fuwa, and Myowa (Royal Society Open Science, 4; 170370, 2017) extended to chimpanzee subjects a paradigm that had been developed by Povinelli and colleagues (Povinelli, Landau, Child Development, 67; 1540-1554, 1996; Perilloux, Povinelli & Simon, Developmental Psychology, 34, 188-194, 1998) to demonstrate the concept of self-continuity in young children. However, Hirata and colleagues lacked critical controls that would have allowed the conclusion that some of their chimpanzees recognized themselves in the time-delayed videos.