1. observing afterimage in a dark room (retinal image stationary, eyes moving)
2. pushing on eyeball but keeping eyes stationary (muscles push back, causing CDS)
3. Pursuit: moving object, eyes move with it (e.g., tracking a car driving past: no IDS)
4. eyes paralyzed, try to move your eyes (retinal image stationary, but CDS sent) Eye cannot move but since the CDS is sent, you get a sense of the room moving