Friday Illusion: Brain builds swinging tower of Pisa

Sandrine Ceurstemont, editor, New Scientist TV

Luckily, if you see a swinging tower of Pisa, it's likely to be all in your mind. A new animation created by Sebastiaan Mathot from VU University in Amsterdam, The Netherlands, exploits a classic brain trick to design a series of columns that seem to sway back and forth. In reality, the towers are always perfectly straight.

The effect is a nice illustration of the way our visual system tends to perceive whole objects rather than their components. Although Mathot's design is actually a bunch of carefully-positioned lines, we initially see the larger bands. "If we see a chair, for example, we don't consider the parts of the chair separately, one at a time," writes Mathot. "In other words, we automatically group objects together into a single, coherent percept."

The tilting column is a result of the way our brain forms groupings based on proximity and similar colour. The misaligned dashes in this video appear as black pairs and white pairs rather than as individual strokes. Then, since the positioning within each grouping is skewed, our brain notices the jagged edge, but simplifies it into a smoother tilt.? By switching the black and white areas in the design, the tilt of the pairs changes direction and the overall columns seem to swing.

Previously, we have shown you other versions of this effect, including: a slanted chessboard and a balance beam that seems to tilt.

Were you able to see this illusion? Let us know in the comments section below.

Source: http://feeds.newscientist.com/c/749/f/10897/s/218cf9cb/l/0L0Snewscientist0N0Cblogs0Cnstv0C20A120C0A70Cfriday0Eillusion0Ebrain0Ebuilds0Eswinging0Etower0Eof0Episa0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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