1) A schedule in which a response is reinforced when either of two (or more) schedule requirements is satisfied (e.g., in alternative FR 10 Fl 60-s, the tenth response or the first response after 1 minute is reinforced, whichever comes first, and both schedule requirements then start over).

2) A response is reinforced on whichever of two schedules is satisfied first (e.g., after 5 minutes has elapsed or after 50 responses have been emitted, whichever occurs first).