At the University of Tokyo, the Ishikawa Senoo Laboratory built a Rock Paper Scissors robot that wins every round by reading the human hand during the throw. In Japan, the game is called janken. Players count together, then reveal rock, paper, or scissors at the same time. The lab’s system uses high-speed vision and a fast robot hand to see the human gesture as it forms and to answer with the winning sign before the reveal finishes. The result is a 100% win rate under standard cadence.
How the System Works
The robot watches your hand with a high-speed camera and a vision loop that runs at roughly one millisecond. That loop detects the shape and position of your fingers as you start to throw. The control system sends commands to a robot wrist and fingers that move almost instantly. While you complete your motion on the count of shoot, the robot finishes a counter throw that beats your sign. Both hands finish together, but the robot has reacted to you during the final fraction of the beat.
Step-by-Step Round
- Count begins, both you and the robot raise your hands.
- The camera tracks your fingers and wrist in real time.
- On the count of three, your shape settles into rock, paper, or scissors.
- The vision system classifies your throw.
- The controller chooses the winning sign and moves the robot hand.
- Both hands complete together, and the robot wins every time.
Why the Robot Always Wins
Humans take about 200 milliseconds or more to react to a visual cue. The robot reacts in about one millisecond. That speed gap means the robot can always answer second yet finish at the same time. It does not predict your move. It simply reacts faster than you can perceive. Randomizing your choice does not help because the robot responds to the actual hand shape in real time.
Key Technologies
- High-speed vision: Detects hand shape and position in one millisecond.
- One millisecond auto pan-tilt: Keeps the hand centered in view across a wide field.
- Lumipen tracking tools: Demonstrate the same control methods in projection mapping.
- High-speed robot hand: Executes precise, rapid counterthrows.
Fairness Under Official Rules
No, it is not fair under official WRPSA rules. In tournament play, both players must reveal simultaneously. A reactive throw like this robot’s counts as late. The project is presented as a technology demo, not as a legal competitive opponent.
Applications Beyond Gaming
The same technology can assist in many fields:
- Factories: Real-time support for complex manual tasks.
- Medical tools: Tremor damping and precise tracking.
- Projection mapping: Keeping visuals locked to moving surfaces.
- Robotics: Improving human-machine collaboration with near-instant reactions.
Timeline
- Early 2010s: First proof-of-concept janken robot.
- Mid 2010s: Faster hardware and better tracking improve reliability.
- Late 2010s: Third version achieves 100% win rate under standard cadence.
FAQ
Does the robot predict my move? No. It reacts to your hand shape in real time.
Can a human beat it by randomizing? No. It responds to the actual shape, not your plan.
Is this legal in tournaments? No. WRPSA rules require simultaneous reveals.
Sources and Related WRPSA Pages
- WRPSA Rules – Official cadence and throw standards
- WRPSA Strategy Guide – Legal competitive play tactics
- Ishikawa Senoo Laboratory – University of Tokyo research
- Janken Robot Demo Video – YouTube
- Wikipedia – Rock Paper Scissors overview