Ghost of a flea

Using indifference curve analysis to show why people stand still on escalators but walk on moving walkways helps establish the near-universal applicability of economic theory. Working with contrasting preference maps (such as those in Figures 1 and 3) to deal with an issue where the student's own intuition is fully in play may help the student to read indifference curves in less intuitive cases. And challenging the students to apply basic economic tools to similarly frivolous issues can result in fun and even learning.

The only down side to exposing students to this armchair view of escalators is that they may never again be able to ride an airport escalator without thinking of indifference-curve analysis.