An article "Time Warp: how your brain creates the fourth dimension" in the 24 October 2009 issue of the New Scientist was particularly stimulating. Taking the 'Wagon Wheel effect' of cinematography which is due to the mismatch between the speed of rotation of the wheel and the frame rate, the author argues that similar effects can be observed due to the operation of the human brain. The human eye collects data as samples and that there is a natural sampling rate within the brain. If data is presented at the edges of the sampling intervals then it is not seen and that this is a large part of the art of the conjurer.

I have observed another form of wagon wheel effect while stopped at a traffic light at a T-junction that includes a pedestrian crossing. In UK these are fenced off. The galvanised rails comprise 10mm square cross-section rods, set 100mm apart as seen in the picture. Now, if from your parked position you watch the progress of a car wheel through the railings, then, depending on the speed of the car you will see the perforations on the wheel rim rotate at a different speed to the wheel itself. Does anyone know if this effect has a specific name?