“In one case, the reinforced glass used for panel shelters (for railroad passengers) erected by British Rail was smashed by vandals as fast as it was renewed.
When the reinforced glass was replaced by plywood boarding, however, little further damage occurred, although no extra force would have been required to produce it.
Thus British Rail managed to elevate the desire for defacement to those who could write, albeit in somewhat limited terms.
Nobody has, as yet, considered whether there is a kind of psychology of materials. But on the evidence, there could be.”
The term *affordance* refers to the perceived and actual properties of things, primarily those fundamental properties that determine just how the thing could possibly be used. A chair affords for (*is for*) support, and therefore, affords sitting.
Glass is for seeing through, and for breaking.
Wood is normally used for solidity, opacity, support or carving. Wood is also for writing on.
Hence the problem for British Rail: when the shelter had glass, vandals smashed it; then they had plywood, vandals wrote and carved it. The planners were trapped by the affordances of their materials.
Affordances provide strong clues to the operation on things. When affordances are taken advantage of, the user knows what to do just by looking: no picture, label, or instruction is required. Complex items may require explanation, but simple things should not. When simple things need pictures, labels or instructions, the design has failed. A poor design can also allow false causality to occur.
— Donald A. Norman - The Design of Everyday Things