The priming phase is the moment between "Rock, Paper, Scissors" and "Shoot" — the three counts when both players are pumping their fist in rhythm and the throw hasn't happened yet. Most casual players treat it as filler. Competitive players treat it as information.
During the priming phase, your body is already starting to commit to the throw you're about to make. The hand begins forming before the final count. A Rock throw starts with the fingers closing. A Scissors throw involves the index and middle fingers beginning to separate. Paper requires the hand to open fully. These micro-movements happen before the reveal, and they're readable to someone who knows what to look for.
This is the physical basis of tells in competitive RPS. A tell isn't something you do intentionally — it's a behavioral leak, the gap between what you've decided to throw and what you've committed to showing. The priming phase is when tells become visible. An opponent who is watching your hand rather than your face during the count has a half-second window to pick up on which shape your hand is already becoming.
The counter is to prime neutrally. Start from a clean, closed fist, pump in rhythm without early movement toward your intended shape, and only commit to the throw at the final count. This is harder than it sounds. The natural tendency is to begin forming the shape as you settle on your decision, which means your decision process bleeds into the physical output. Players who have short decision times — who pick their throw early in the count — tend to show longer priming tells than players who decide late and commit fast.
Advanced players also use the priming phase offensively. Deliberate false priming — beginning to form one shape, then switching at the final count — is a bluffing technique that requires significant practice to execute cleanly without violating timing rules. A move that isn't fully committed on "Shoot" is subject to referee review. The risk is a timing violation. The reward is an opponent who read your prime and countered it, only to find you threw something different. It's one of the few reliable deception techniques in the sport that operates within the rules when executed correctly.