Here’s a place to collect gifs of the Pi – Diagonal Drift signal, which is described thusly: “The eyes and head drift off diagonally to the side or floor, and then return again to a forward facing position."
The gifs don’t need to show just this one signal in isolation, necessarily – as long as the relevant signal is clear.
Here’s a gif of Bill Nye, who is in the database as SiFe l--l, doing a diagonal drift.