Illusory Blob

Here we simulate a black triangle in front of white lines. In one case, the triangle is stationary and the lines rotate. In the other case, the triangle rotates and the lines are stationary. You should see a difference: the rotating triangle appears as a deforming blob, wheras the stationary triangle is more readily seen as such (Bruno & Gerbino,1991). In these, as in many other phenomena, the visual system uses spatiotemporal information to recover contours that would otherwise be invisible. However, this process yields veridical results only if certain motion components are available. In this case, when the lines rotate there is a local component that translates along the occluding edge of the triangle. This component seems critical. In its absence, the visual system is unable to recover the triangle from the accretion/deletion of the lines.

created by Fauzia Mosca and Nicola Bruno