Hopefully interactions will be at a higher level of abstraction than programming a computer.
A computer is a high-speed moron, and I really should give the standard moron more credit. A good method of teaching this principle is to have the parts to make a PB&J, all on a table in front of you (a knife, bread in a sack, closed jars).
Have the class try to guide you thru the sequence. Act *exactly* as told. "Pick up the bread": pick up the unopened sack and keep raising it until you cannot go any further, then fall against the wall (you should have a wall behind you, but YMMV :^)
How long you do this exercise depends, of course, on the age of the class. But they *will* get the point after enough frustration.