Thursday, 12 April 2018

troxler fading

TYWKIWDBI introduces us to a curious optical illusion that occurs when one focuses at the single black dot in the centre of this image with the wash of colours surrounding it will disappear after about twenty seconds of uninterrupted staring. Click on the image to open it in a separate screen in case there is distracting marginalia on the page.  The visual effect which happens at least in part in the brain (and not in the eyes) was first identified and described by Viennese physician and philosopher Ignaz Paul Vital Troxler and is explained as the perceptual neurons (there are parallel effects for the other senses besides just sight) become inured to an unchanging background and begins to ignore it.
The above animation illustrates a variant of Troxler fading called the Lilac Chaser, credited to Jeremy Hinton circa 2005, and you’re invited to stare at the black cross-hairs for about thirty seconds and see what happens. Clinically and metaphorically, learning about ways that our perceptions are liable to compromise we’re finding simultaneously enlightening and leaving us wondering how we might be benighted.