This kind of system is inherited by both animals. Example: a fledgling bird does its releaser, say it squawks and opens its beak wide, showing bright red inside throat. This triggers the adult to cough up food stored in its gullet. Both 'partners' are behaving instinctually with inherited behaviours: these are not learnt during life. A FAP can truly be said to be 'hard-wired': a specific stimulus nearly always results in the same behavioral response.