Benham's top

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Gustav Theodor Fechner (1801—1887) German physicist and psychologist

Isaac Newton (1642—1727) natural philosopher and mathematician

Sir David Brewster (1781—1868) natural philosopher and academic administrator

Hermann Ludwig Ferdinand von Helmholtz (1821—1894) German physiologist and physicist

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A black-and-white patterned disc that induces perceptions of colours, called pattern-induced flicker colours (PIFCs), when rotated in white or monochromatic light. The basic design (on which there are many variations) consists of a disc divided into black and white halves, with a triplet of concentric black arcs in each of four equal sectors of the white half, the arcs in the first sector being close to the circumference, and the arcs in each of the succeeding sectors being closer to the centre than the arcs in the previous sector (see illustration). The top produces visual illusions of bright colours, especially when rotated at 5–10 hertz (cycles per second), the colours of the arcs from the circumference to the centre being either red, green, blue, and violet; or violet, blue, green, and red, depending on the direction of rotation. The top stimulates adjacent areas of the retina at the same frequency but with slight phase differences, black following white at different points in each revolution of the top, and the perception of colours is believed to originate from retinal neurons that form lateral connections between such areas and are phase-sensitive, although research using dichoptic stimuli has shown that brain processes may also play a part. The top was marketed as a toy in Victorian England. Also called Benham's wheel. See also colour induction, Fechner-Benham colours. [Named after the English amateur scientist and polymath Charles Edwin Benham (1860–1929), whose ‘artificial spectrum top’ was discussed in the journal Nature in 1894, although unknown to Benham it had already been discovered by the German philosopher, physician, psychologist, and mystic Gustav Theodor Fechner (1801–87), who published his findings in 1838]

Benham's top

Subjects: Psychology.

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