Is there a name for the psychology behind lowering your bets? I'm having a hard time phrasing my question into words, so I'll provide an example:

Imagine you ask someone how much it'll take to eat a worm. The person says they would eat a worm for \$20. Instead of offering \$20, you offer 1 dollar less. Reluctantly, they say yes to \$19. You proceed to offer 1 dollar less so on and so forth. Eventually the reward money draws close to \$0 and we're left with a bizarre situation.

Is there a name for this phenomenon or am I totally bananas?
The answer I was searching for is Creeping Normality. It fits better examples and has a clearer definition for what I was attempting to express.


  Creeping normality refers to the way a major change can be accepted as
  the normal situation if it happens slowly, in unnoticed increments,
  when it would be regarded as objectionable if it took place in a
  single step or short period.