ABOVE: The SNARC machine included 40 artificial neurons (one pictured), which were interconnected via a plugboard and held in racks in a contraption about the size of a grand piano. At one end of the neuron was a potentiometer (bar on far right), a sort of volume knob that could adjust the probability that an incoming signal would result in an outgoing signal. If the neuron did fire, a capacitor (red) on the other end of the neuron retained a memory of the firing for a few seconds. If the system was “rewarded”—either by the researchers pushing a button or an electrical signal from an outside circuit—a chain connected to the volume knobs for all 40 neurons would crank. This would cause the volume knob to increase the future probability of the neuron firing, but only if a magnetic clutch had been engaged by a recent firing.
COURTESY OF MARGARET MINSKY
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