|InfoVis.net>Magazine>message nş 79||Published 2002-03-04|
|También disponible en Espańol|
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Last february, 26th we discovered that Donald Rumsfeld, USA secretary of Defense had definitively closed the Office for Strategic Influence, apparently after an issue of the New York Times that revealed the disinformation plans that the already mentioned office planned to put into practice, including the delivery of false information to periodical publications outside the USA. This news made me think about the role of lies or, if you prefer to say it the subtle way, disinformation in connection with visualisation.
Edward Tufte devotes a whole chapter of his excellent book â€śThe Visual Display of Quantitative Informationâ€ť to â€śGraphical Integrityâ€ť, where he disassembles some of the tricks that allow you to lie subtly with graphics. For example he defines a â€ślie factorâ€ť as the ratio between the size of the visual effect that the graphic depicts and the size the effect has in reality.Â
As a classical example, the chart showing the shrinking purchasing power of the dollar between 1958 and 1978 appeared in the October, 25, 1978 issue of The Washington Post. The chart shows 5 one dollar bills each of them with a length proportional to the purchasing power at its time ( see the adaptation of the chart) .Â
In this case, while the variation of the purchasing power varies in just one dimension, the visual effect is the one associated to the area of the bill, that is two dimensional. This way the smallest bill, one 1978 dollar, is worth 44 cents of a 1958 dollar. Its length is, correctly, 44% of the biggest one that represents a 1958 dollar.Â
Nevertheless its area is just 19% of that of the biggest one. This gives the impression of a dramatic reduction of the purchasing power. In order for the area to reliably represent the value, the size of the 1978 bill should be about twice as big as that shown.
Howard Wainer, in his book â€śVisual Revelationsâ€ť develops 12 rules in order to represent data badly, that are based on the negation of the 3 principles that define a good graphic. Since a good graphic shows a lot of data in little space, in a precise and clear way, if you want to disinform:
The twelve rules that follow from these principles are (with some literary licenseâ€¦):
Obviously, turning the twelve rules upside down helps, although doesnâ€™t guarantee, to make more accurate and clearer graphics that reveal the data and its differences. On the other hand it helps to stand the impact of the image and to build a critical turn of mind that could allow us to detect the tendentious and confusing graphics that populate many presentations that too many times we accept quite happily.
Visualisations are not neutral, they depend on our selection and on what we want to show the others and to ourselves. Cultivating this critical turn of mind regarding what we do and what others show to us is vital to avoid confusion.
Three amusing and interesting books that are worth reading:
Links of this issue:
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