Sunday, 28 December 2008

Optical Illusions

Spinning wheels...

If you focus on the picture, all the wheels start to spin (in both directions). However, if you then concentrate on a single wheel, that wheel will stop whilst the others keep turning.

Look closely, the orange circles are the same size...

An illusion that plays on our perception of relative size. The first central circle appears smaller than the circle on the right yet they are identical in size. This is the Ebbinghaus Illusion.

First described by the British psychologist, James Fraser, in 1908 this is known as the Fraser Spiral Illusion. The overlapping black arcs appear to form a spiral; but, the arcs are simply a series of concentric circles.

An example of the Zollner Illusion. The long black lines are in fact parallel to each other. The illusion is created by the shorter lines being at an angle to the longer lines, this creates the impression that one end of the longer lines is nearer to us.

In this image, the two shapes are in fact identical in size. The Jastrow Illusion was discovered by Joseph Jastrow, the American psychologist, in 1889.

First discovered in 1860 by Johann Poggendorf, the Poggendorff Illusion, illustrates how the brain can be tricked by the interaction of diagonal and horizontal lines. At first viewing, one assumes that the blue line is a continuation of the black line. However, on closer viewing it is actually the red line.

Known as White's Illusion, is a counterintuitive illusion. When a grey rectangle is mainly surrounded by black it should look lighter. In this case, the grey rectangles are exactly the same shade of grey.

A Motion Illusion. The brain's reaction to the colour contrasts and position of the shapes is such that this static image appears to be moving.


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