The use of illustrations in charts—instead of bar or lines—might change the perception viewers have of the information. When the value in the chart is represented by length, the use of size-changing figures is a problem, because they add the dimension of width. That is, instead of comparing lengths, the viewers are led to compare areas, which is a distortion of the linear data. Even further, the viewers have a three-dimensional notion of the illustrated object, which may increase their perception to volumes. Therefore, a growth of 2 times may be seen as a growth of even 8 times.

The example shows the relation between the production of hats by the Mad Hatter (from Alice in Wonderland) and the amount of sugar he consumed in his tea. In the chart on the left, the amount of produced hats is shown with an illustration representing a hat, while the amount of sugar is represented by an illustration of a spoon. The charts compare data from two days—Saturday and Sunday—in order to establish a relation between the sugar and production of hats.

So that the figures are not distorted, they change not only in length but also in width from Saturday to Sunday. That way, the Sunday looks enormous comparing to the previous one, which makes it look like the growth in hat production was a lot bigger than the actual 50%. And, since the hat is rather wider than the spoon, its change in area from Saturday to Sunday is more ostensible. It might cause the impression that the production of hats has grown more than the consumption of sugar, even though they have grown in the same rate.

So that the use of illustrations does not distort the data, the focus should be on only one dimension. Instead of using the size of figures to compare amounts, the chart can employ repetition of same size icons. The chart on the right is more accurate, for it utilizes repetition of figures. The spoons and hats occupy the same width, which brings the focus to the changes in length.