The mistake of introducing meaningless variety into a dashboard design is closely tied to the one we just examined. I've found that people often hesitate to use the same type of display medium multiple times on a dashboard, out of what I assume is a sense that viewers will be bored by the sameness. Variety might be the spice of life, but if it is introduced on a dashboard for its own sake, the display suffers. You should always select the means of display that works best, even if that results in a dashboard that is filled with nothing but multiple instances of the same type of graph. If you are giving viewers the information that they desperately need to do their jobs, the data won't bore them just because it's all displayed in the same way. They will definitely get aggravated, however, if forced to work harder than necessary to get the information they need due to arbitrary variety in the display media. In fact, wherever appropriate, consistency in the means of display allows viewers to use the same perceptual strategy for interpreting the data, which saves time and energy.
Figure 3-18 illustrates variety gone amok. This visual jumble requires a shift in perceptual strategy for each display item on the dashboard, which means extra time and effort on the user's part.
Figure 3-18. This dashboard exhibits an unnecessary variety of display media.