Here’s a dark-on-light, bubble version of The Kanizsa triangle.  The triangle is usually shown in white against black circles and lines, and can even look slightly brighter than background, though its edges are only indicated by the gaps in the lines and by the segments missing from the circles.   The brain adds the edges and fills in the triangle, as the most probable explanation for what’s missing.  The effect was created by Gaetano Kanizsa, as a demonstration of subjective contours, which in turn were first explored a bit over a century ago, as examples of Gestalt theory.  Bit of a link for enthusiasts that – ditto the following links – but if technical stuff is for you, there’s a great historical survey of the theory.  The theory as then developed is not now accepted, and just how the brain reconstructs the triangle is still debated.

Like many geometric illusions, and like the watercolour illusion (see recent post), the Kanizsa triangle also appears when reversed out as a black shape against bright lines and segments.  So here I’ve recruited some soap bubbles as a background to the effect.

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