Janken Column

Trivia, history, and small surprises about rock-paper-scissors.

• 🌍

  Why "saisho wa guu" doesn't translate — janken variants around the world

  Janken looks like a simple three-hand game, but variants stretch from Edo-era Japanese parlor games to Lizard-Spock and beyond.

• 🧠

  Janken isn't really 1-in-3 — what psychology says about hand bias

  It looks like a fair coin flip with a third option, but human players reveal surprisingly consistent biases — and a strategy called Win-Stay, Lose-Shift.

• 🏆

  The World Rock Paper Scissors Championship — when janken had pros

  From 2002 to 2009, the World RPS Championship in Toronto crowned annual winners with cash prizes. Yes, professional rock-paper-scissors was a thing.

• 🦎

  Janken in the wild — the side-blotched lizard's three-color mating cycle

  Side-blotched lizards in the American west have three throat colors that beat each other in a perfect rock-paper-scissors cycle — janken really does exist in nature.

• 🤖

  The 100% janken-winning robot — Tokyo's high-speed vision benchmark

  Tokyo University's janken robot has a 100% win rate against humans — not by cheating but by reading the hand shape in 1 millisecond, a high-speed vision research demo.

• ⚖️

  The judge who ordered "settle this with rock paper scissors" — a real US case

  Frustrated by lawyers bickering over a deposition venue, a US federal judge actually ordered them to settle it with one game of rock paper scissors. 2006, on the record.