Motion Binding
What to observe
Look at the blue lines above. They move, yes, and what kind of shape do they represent?
I would say they move in pairs.
What to do
Click on the “Occluders on” radio button. Now the blue lines suddenly outline a
diamond, which moves in a circular fashion!
Please note: the motion of the blue lines is exactly the same, regardless whether
the green occluders are green or have the background gray (=invisible). Our percept,
however, undergoes a striking change.
Clicking on “Slider” allows you to set the gray value of the occluders: just a little
bit off background, and the blue line combine to a diamond. There is also some hysteresis
here.
More to try: make the green occluders invisible, so that you see the two blue line
pairs rather than the diamond, and then look at the left end of this page and not
on the demo, but observe it with your “inner eye”. Now the moving image (somewhat
blurred because viewed eccentrically) will look more like a rotating diamond rather
than two unconnected line pairs.
Comment
Technically the mechanism at work here is known as “motion binding”. When the edges
of the diamond are covered by occluders with the same colour as the background (here,
white) there is no information on the vertices of the square. Now the ends of the
line become a property of the line and there is insufficient information to detect
the circular movement.
The reappearance of the diamond (with occluders invisible) on eccentric viewing
is probably caused by blurring the distracting line ends.
Sources
Adelson EH, Movshon JA (1982) Phenomenal coherence of moving visual patterns. Nature
300:523–525
Lorenceau J, Shiffrar M (1992) The influence of terminators on motion integration
across space. Vision Res 32:263–275
Lorenceau J, Alais D (2001) Form constraints in motion binding. Nature Neuroscience
4:745–751
McDermott J, Weiss Y, Adelson EH (2001) Perception 30:905–923. I recently found
their associated website with fine demos.
Mosca & Bruno have a similar demonstration in their nice collection
on motion perception
Kanwar Plahar prompted me to draw attention to eccentric viewing, which had already
been described by Lorenceau & Shiffrar (1992).
Created: 2005-10-03
Last update: 2013-10-04