Just recently we were discussing the wagon-wheel illusion, and if I recall correctly, both Tom Alloway's students and Beth Benoit reported seeing the phenomenon under steady illumination while driving down the highway.
By coincidence, there's a report just out (well, I just spotted it anyway) investigating the phenomenon. They say it doesn't occur under steady illumination under laboratory conditions. So students of Tom and Beth, science says you didn't see what you saw. I append the abstract below. It has the distinction of coming from theoretical physicists and from Iran, a rather unusual source on both counts, it seems to me. If I may speculate on the discrepancy between what science found and what people experienced, I wonder if under real-life conditions such as driving down the highway, what appears to be steady illumination may actually be flickering. For example, if the light illuminating the wheels was interrupted by trees or by posts along the highway, it would flicker, and so understandably cause the effect. I seem to recall that epileptic seizures have been triggered in susceptible individuals by such flickering when driving down a road lined with trees. Stephen Perception. 2003;32(11):1307-10. Wagon-wheel illusion under steady illumination: real or illusory? Pakarian P, Yasamy MT. School of Intelligent Systems, Institute for Studies in Theoretical Physics and Mathematics (IPM), Niavaran Square, Tajrish, Tehran, PO Box 19395-5746, Iran. [EMAIL PROTECTED] 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. ___________________________________________ Stephen L. Black, Ph.D. tel: (819) 822-9600 ext 2470 Department of Psychology fax: (819) 822-9661 Bishop's University e-mail: [EMAIL PROTECTED] Lennoxville, QC J1M 1Z7 Canada Dept web page at http://www.ubishops.ca/ccc/div/soc/psy TIPS discussion list for psychology teachers at http://faculty.frostburg.edu/psyc/southerly/tips/index.htm _______________________________________________ --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
