Silencing by Motion
What to see
On the above, there is a rotating ring consisting of many coloured discs; best fixate
the central cross. Notice anything special? Well, the ring changes rotation direction,
we all can easily agree on that.
What to do
Press the ‘stop’ button. Unsurprisingly, the ring
refrains from rotating. Now it becomes obvious that all the small disks change their
colour; going through rainbow so to speak.
Starting the ring rotation now and looking closely reveals that the colour change
happens all the time, but it is barely noticable during rotation. This can be demonstrated
by pressing the ‘hue±’ button during rotation; this
has nearly no effect during ring rotation.
Comments
This effect was published early in 2011 by Jordan W. Suchow and George A. Alvarez
from Harvard University. It subsequently won, deservedly, the “Best Illusion of
the Year Contest”.
In the paper by Suchow and Alvaraz and their 2011-VSS poster, not only interesting
variants but also several concrete mechanisms are discussed and tested, which I
need not go into here. An intuitive explanation: processing global motion presents
an overload, which impairs coding of the local details. This is a really new effect,
and I think it may be related to “motion blindness”.
A new paper (Turi & Burr 2013) reports that (1) there is a speed threshold (0.2
rps {depending on the absolute spatial arrangement}) and (2) crowding explains the
silencing (crowding: “the fact recognition of target in the periphery is difficult
when surrounded by other stimuli”). Crowding is well established also for central
vision (where small details are more difficult to detect when more details are nearby),
but becomes stronger at larger eccentricities.
Sources
Suchow JW, Alvarez GA (2011) Motion Silences Awareness of Visual Change.
Current Biology 21:1–5.
That provides links to demonstration movies with a number of interesting variants.
You can find them also at their demonstration page.
Burr D (2011) Visual Perception: More Than Meets the Eye. Curr Biol 21:R159–R161
(thoughtful editorial)
Peirce
JW (2013) Is it just motion that silences awareness of other visual changes?
JOV 13:7, 17
Turi M, Burr D (2013) The “motion silencing” illusion results from global
motion and crowding. J Vision 13(5):14, 1–7
I am thankful to Jordan for gracefully allowing me to present
this demonstration, closely modeled after their publication.
Created: 2011-05-13
Last update: 2013-10-04