While working on a paper on neural computation, the following question came up: can you exert feedback control without processing information?
The kind of case I have in mind is that of relatively simple feedback control devices that use one or two physical variable(s) to affect another. For instance, Watt governors or float regulators that maintain the level of a liquid within a container at a stable level by opening or closing a valve based on a flotation device linked to the valve. When the valve is open, liquid comes in, raising the flotation device and shutting the valve. When the valve is shut, liquid stops coming in. If the liquid goes down again (e.g., because someone flushes the toilet), the flotation device goes down, the valve opens up, and liquid starts pouring in again.
It seems to me that in these control devices there is nothing that deserve the name of information processing. That is, no variables are processed based solely on the information they carry as opposed to their specific physical characteristics. If you want to fix a malfunctioning float regulator, you can’t intervene solely on a hypothetical information-processing part of the process; you just have to adjust the variables based on their physical interaction (e.g., you might change the angle between the arm that holds the flotation device and the arm that opens the valve). Or to put it yet another way, there is no transduction of physical variables into medium-independent variables.
If this is right, then feedback control does not entail information processing (in the general case).
At the same time, if you need to exert feedback control functions of serious complexity, involving the interaction of several input and output variables, the only efficient way of doing so seems to be to transduce all the input physical variables into some internal variables that can be manipulated based on the information they carry and process those. Thus, feedback control beyond a certain complexity requires information processing.
I’d be very interested in any comments that anyone might have. What am I missing?