Optical Perceptions

Ternus Display

In this illusion, three blue disks jump back and forth across the screen. At first, it seems like the leftmost disk simply hops to the right end and back again. As you increase the ISI (inter-stimulus interval) using the slider, a blank pause appears between frames. As the delay grows, your perception begins to shift: the entire group of disks seems to move together, rather than a single disk jumping alone. This change from “element motion” (short ISI) to “group motion” (long ISI) reveals how the brain links separate frames of motion over time — even when color tags show which disk actually moved.