What is true about fixed action patterns after initiation?

• A. They can be interrupted without consequence.
• B. They must go to completion once started.
• C. They are always voluntary and reversible.
• D. They are only triggered by human commands.

Answer: (B)

Fixed action patterns are instinctive, species-typical sequences of behavior that, once released by a sign stimulus, unfold to completion because they’re driven by a hardwired program in the nervous system. Once you start one, the animal typically carries the entire sequence through to its final element, even if the triggering cue is removed or the situation changes. This persistence to completion is what characterizes a fixed action pattern, distinguishing it from voluntary or flexible behaviors. They’re not voluntary and aren’t triggered by human commands; examples include a goose’s egg-removal and retrieval sequence or a stickleback fish’s attack pattern triggered by a specific cue.