The very existence of this research puzzles me. When I got a cat, I named him "kot" (a male cat in Russian), cause I thought he wouldn't remember it, so why bother. But he learnt it in a week. I just made my own research, for the sake of this comment: said "Petya", "Idi syuda, durak" and "kot", and sure enough, after the third call he came, sat beside me, and is now watching the screen.