Wagon wheel illusion

[Pooya Pakarian]

Wagon-wheel illusion under steady illumination: real or illusory?
Pooya Pakarian, Mohammad Taghi Yasamy
Perception 2003, volume 32, number 11, pages 1307 - 1310

Abstract. Wheels turning in the movies sometimes appear to rotate 
backwards. This is called the wagon-wheel illusion (WWI). The mechanism 
of this illusion is based on the intermittent nature of light in films 
and other stroboscopic presentations, which renders them as a series of 
snapshots rather than a continuous visual data stream. However, there 
have been claims that this illusion is seen even in continuous light, 
which would suggest that the visual system itself may sample a continuous
visual data stream. We examined the rate of this putative sampling and 
its variations across individuals while in different psychological 
states. We obtained two results: (i) WWI occurred in stroboscopic lights 
as expected, (ii) WWI was never reported by our subjects under continuous
lights, such as sunlight and lamps with DC power source. Thus, WWI cannot
be taken as evidence for discreteness of conscious visual perception.

This article can be downloaded from
http://www.perceptionweb.com/perc1103/
or easily just by contacting the corresponding author.
( pooyapakarian at ipm.ir, pooyapakarian at yahoo.com )

Pooya Pakarian,MD
School of Cognitive Sciences(SCS)
Institute for studies in theoretical Physics and Mathematics(IPM)
Niavaran Sq., Tehran, Iran.
P.O.Box 19395-5746