Here is an image showing more of the marks of our daily actions accumulating to reveal a frequency distribution of use. Above is a view of the trunk of a county sheriff’s car before its spring cleaning. Road grime allows us to see a pattern of the sheriff’s actions. The officer closes the trunk consistently with the same motion targeted at the same place. This results in a tight pattern of use with little variability and few dirty fingers.
Compare these actions with those of the driver below.
This hybrid owner closes the trunk in many ways, on the left, on the right, perhaps with two hands. The erased road grime displays a much more variable pattern of use, almost uniformly distributed across the trunk opening, making the owner’s fingers dirty often.