1. Dynamic Occlusion
(How Information Tells You About What Is Happening Now)

2. Move the boxes around to make the illusion yourself
Pro tip – move the bigger box, as in Powerpoint selecting the small one adds a border the messes with the effect

3. Press the space bar to show the animation
Push space, get animation of square moving in a circle
Press the space bar to show the animation

4. Kinematics Can Specify Dynamics
Progressive Occlusion (Gibson et al, 1969; Kaplan, 1969)
Dynamical Event: One surface going out of view behind another (becoming progressively occluded but continuing to exist)
Kinematic Information: Deletion of optical texture at the leading edge, accretion of optical texture at the trailing edge (optical elements going being destroyed and created)
Perception: the dynamical event ‘persisting surface becoming occluded and de-occluded’
Judgments: people never report the accretion or deletion, but the occlusion
Multiple object tracking: can still be tracked through an occlusion but not an actual disappearance/reappearance (Scholl & Pylyshyn, 1999)
Scholl & Pylyshyn (19990

5. Multiple Object Tracking Survives Occlusion but not Disappearing
MOT: Occlusion Baseline

6. People track objects
Occlusion specifies moving in and out from behind something Implosion/explosion specifies coming in and out of existence James J Gibson (1966)
Scholl, B. J., & Pylyshyn, Z. W. (1999). Tracking multiple items through occlusion: Clues to visual objecthood. Cognitive Psychology, 38,

7. The particular kinematic pattern (optical texture elements going out of view along a leading edge, into view a long a trailing edge) is detected and leads to the perception of ‘one object passing in front of another with both continuing to exist’