Optical illusion demonstrates how visualisation can trick us

A video of a man moving two pieces of his son’s toy train tracks has gone viral this week


The effect is baffling and is an example of a little understood phenomenon known as the Jastrow Illusion.

In his explanation published in 1892, Jastrow concluded as follows: “We judge relatively even when we most desire to judge absolutely.”

As an earlier post on this blog explains, empirical research conducted on graphs and the human visual system published in the journal “Science” in 1985 proposed a rank order for methods of encoding quantitative data in terms of the accuracy of perception of the values.  The good old fashioned bar chart and line chart came at the top. The researchers found that the use of area to encode data is perceived with much less accuracy, being ranked only five out of seven in the various methods of encoding data that they studied.

This insight is of great importance when considering the most appropriate visualisation to select to convey the business message

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