The homeostat was an electromechanical device built by W. Ross Ashby at Barnwood House Hospital in Gloucester and first demonstrated in 1948. Time magazine called it “the closest thing to a synthetic brain so far designed by man”.
How it worked
It consisted of four identical units, each with a magnet-driven needle floating in a trough of water. The units were cross-connected, so the position of each needle affected all the others. If a needle moved too far from the centre (its essential variable going out of bounds), a uniselector, a stepping switch taken from telephone exchanges, changed that unit’s connections at random. The machine kept switching until it found a configuration in which all the needles stayed near the centre.
Whatever was done to it (reversing connections, adding constraints, coupling the units differently), the homeostat would eventually find a new stable state.
Why it mattered
Ashby called this behaviour ultrastability: a system with a second feedback loop that changes the first loop’s parameters when the essential variables are threatened. It showed that adaptive, apparently purposeful behaviour could arise from trial and error without a designer specifying the solution. Ashby set out the theory in Design for a Brain (1952), and the homeostat became one of the iconic machines of British cybernetics, alongside W. Grey Walter’s tortoises.
Further reading
- W. Ross Ashby, Design for a Brain (1952)
- Andrew Pickering, The Cybernetic Brain (2010), chapter 4
Mentioned in
- Person W. Ross Ashby
- Concept First-order cybernetics
- Concept Homeostasis
- Community Ratio Club