The following screens are a demonstration of how interaction between human tendencies and material design can predispose to errors.
The Stroop Test provides insight into cognitive effects that are experienced as a result of attentional fatigue. The effect was first noted by John Ridley Stroop in his Ph.D. thesis published in 1935. The test emphasizes the interference that automatic processing of words has on the more mentally "effortful" task of naming the colors.
The Stroop task takes advantage of our ability to read words more quickly and automatically than we can name colors. If a word is printed or displayed in a color different from the color it actually names -- for example, if the word "red" is written in blue ink we will say the word "red" more readily than we can name the color in which it is displayed, which in this case is "blue." The cognitive mechanism involved in this task is called inhibition; you have to inhibit or stop one response and say or do something else.
For an interactive version of this test (requires Shockwave) go to www.snre.umich.edu/eplab/demos/st0/stroopdesc.html
This is an obvious demonstration of how a simple task, if set up in an unfavorable way, can be very prone to error.