Requires memory search or reminding Learning Learning not required. Interpretation substitutes for learning. How easy it is to interpret information in the world depends upon how well it exploits natural mappings and constraints. Requires learning, which can be considerable. Efficiency of use Tends to be slowed up by the need to find and interpret the external information Can be very efficient.
Nothing needs to be visible, which can be aesthetic.
Signal vs. message. An alarm by itself does not tell you what it means. On Saturday, the parent plans to go to the Jones' house, but ends up at the school. Wide Structures Everyday activities tend to be either narrow or shallow or both.