Jackpot
A much larger payment than usual, delivered for a genuinely hard success, so the dog knows which repetition mattered.
Also called: big reward · bonus
Not everything a dog gets right is worth the same. Coming back from twenty metres away while another dog is playing is not the same as a sit in the kitchen, and paying both with one piece of kibble teaches a dog nothing about which one to repeat.
A jackpot is deliberately conspicuous — several pieces in a row, or the thing the dog actually cares about most. It is a rate of pay, not a mood.
Used on every repetition it stops meaning anything, so it is reserved for the breakthroughs.