veriscope

He usually manages to twist his head sufficiently when lodged on my shoulder to make it impossible for me to work out whether he's asleep or not even by trying to twist round and look in a reflective surface if there's no-one about to check his eyes for me. Occasionally an accidental loud noise or apparently-measurable acceleration will indicate (by the presence of a startle-reflex twitch) apparent sleepingness but such twitches often denote the end of such a state.