Monday, October 09, 2006

Psychophysics, according to Hoyle

Intriguing letter in last week's Nature on how an aside in the great Fred Hoyle's early SF novel The Black Cloud proved hugely influential in perceptual research -

The characters in the book discover an ominous black cloud that appears to be heading towards Earth. Will the cloud hit Earth and, if so, when? The first question is solved when the characters examine the relative speed at which the cloud is translating across the night sky to the rate at which it is looming, or seeming to get larger. The second question is tackled with a bit of impromptu algebra in which the time until impact is calculated from the ratio of the current size of the cloud to its rate of change. A mathematical derivation of the formula is provided.
A footballer wishing to head an approaching ball needs to know where the ball is going relative to the head, and when it will hit or pass the head. The player could estimate the trajectory of the ball from knowledge of its position and velocity. However, David Lee realized in the 1970s that the brain can use the ratio of size to its rate of change, previously identified by Hoyle, to estimate the imminence of arrival. David Regan realized soon afterwards that the brain can use the ratio of lateral speed to looming rate to calculate where an object is travelling. [...]
Since the early work of Lee and Regan, a considerable amount of research in areas including psychophysics, motor action, neurophysiology and computational modelling has followed. The whole body of work that exists today can be traced back to a casual footnote and a couple of sketches in a science-fiction novel.

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