Logic gates made of live crabs

In Robust Soldier Crab Ball Gate, recently published in Complex Systems, a Japanese-UK computer science team describe how they made functional logic gates by constructing a maze of narrow tunnels and spooking soldier crabs into running through them in predictable ways by exposing them to bird-of-prey silhouettes. Lead researcher Yukio-Pegio Gunji (Kobe University) and colleagues implemented a "billiard ball computer" (a computer that implements logic gates out of chutes through which balls are dropped, either colliding or falling straight through) using the crabs, who have a repertoire of deterministic flocking responses to various stimuli, including narrow passages and the presence of predator shadows. The result is a relatively functional AND gate and a less-reliable OR gate. A Technical Review blog summarizes the method well:

When placed next to a wall, a leader will always follow the wall in a direction that can be controlled by shadowing the swarm from above to mimic to the presence of the predatory birds that eat the crabs.

Under these conditions, a swarm of crabs will follow a wall like a rolling billiard ball.

So what happens when two "crab balls" collide? According to Gunji and co's experiments, the balls merge and continue in a direction that is the sum of their velocities.

What's more, the behaviour is remarkably robust to noise, largely because the crab's individuals behaviours generates noise that is indistinguishable from external noise. These creatures have evolved to cope with noise.

That immediately suggested a potential application in computing, say Gunji and co. If the balls of crabs behave like billiard balls, it should be straightforward to build a pattern of channels that act like a logic gate.

Computer Scientists Build Computer Using Swarms of Crabs (via Wired)



  1. I think the only remaining question is – do they win the Biology Ig Nobel prize or Computer Science?

  2. It’s all fun and crustacean computing until they achieve a critical mass of shelled panic then leap out of the chute and eat your face.

  3. The article linked has the reliability of the AND and OR gates the other way around:
    “While Gunji and co found they could build a decent OR gate using soldier crabs, their AND-gate was much less reliable. ”

    Well, I can see how the OR gate would work better, as the crabs don’t have a choice but take the “correct” gate, so it would just be a matter of if they both continue down that chute (or not) as a “ball”. In an AND gate there is more choices so also more ways where it can go wrong. But… uuh… yeah…. and this was relevant computer science exactly how? To study the behaviour of Soldier Crabs… sure, I can definitely see the value in that. But computer science? Edit: And to be relevant to computer science… how on earth do you build the “NOT” type gates?

    Can I apply for a grant to study if I can make reliable logic gates by placing a bottle of soda and some chips at the end of corridors and make my fellow programmers make a run for it?

    1. Computer chips are very small. Crabs are quite large in comparison, so they can build a giant simulation of a computer chip out of crabs, and observe in real time how computers work. Because until now, computers were like magnets, as far as that goes.

  4. My geek friends and I used to design logic gates out of various things: steam valves, mirrors, marbles, differently weighted liquids, sounds waves, springs, and others things but none of us once came up with the idea to use live animals. I think this is awesome.

  5. Mmm, I think these logic gates would taste better cooked in salted duck egg.  I hear they make ’em that way at Lala Chong in KL.

  6. Would this work if you swapped the computer science team for a gaggle of marketeers, the crabs for brainwashed consumers, and the maze with an appropriately-designed shopping mall…?

  7. “Hello, help desk? I can’t get my crab computer to work.”
    “Did you open another shell?”
    “Yes, but it’s cracked.”
    “What about your web crawler?”
    “That’s my spider computer; it’s working fine.”
    “Is it a King Crab platform?”
    “No, that’s my mainframe.  This one’s just a softshell.”

    1. I was thinking about the ramifications of this technology should it ever supplant regular silicon ships.  “Poor Dave.  He had a stack overflow and was pincered to death.”

  8. Everyone’s been talking about this “clawed computing”,  thing and I thought they were saying “cloud”.  Now it all makes sense.  

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