The Subjective Nature of Objectivity

The image above is constructed from about 7,000 randomly placed dots. In a sequence of frames, the dots in a square were randomized again, such that each of the subsequent frames has a different randomization pattern in a selected square area. The squares selected for randomization were constructed from 1/10 of the X and Y values progressively from the lower left to the upper right along the diagonal of the matrix. Dots change randomly within the succession of squares, but no dots move along the diagonal, despite the appearance that they do.

Stay still froggie or a predator might see you!

The images below appear to contain random dot patterns. These are the first frames from movie (.mpg or .mov) files which you can download by clicking on any of the images. I suggest that you configure your player to loop or recycle.

When you view each frame as a still image there is no hint of a disk shaped object. In the movie, frames are shown in rapid succession and a disc appears to bounce from left to right across the screen. The frame to frame displacement of a group of dots is sufficient disparity to cause us to organize the dots into a moving object. In the oval images above and below, the displacement is a rotation of the dots around a point.

Gestalt psychologists called grouping phenomena like this one, "Common Fate".

You can manually step through frames at transition rates that allow you to see the object seem to disappear.

You might want to see:

Michael Bach's Structure from motion at equiluminance

George Mather's site on motion

Click on the 'View more' link on this page about studies of motion at Vanderbilt University

Demo by Lee & Blake: Spatial Structure from Temporal Synchrony

Demo 2 by Lee & Blake: Spatial Structure From Temporal Structure

Demo 3 by Lee & Blake: Spatial Structure From Temporal Structure: Rotation

Demo 4 by Lee & Blake: Spatial Structure From Temporal Structure: Entropy

to the Illusion page