Cellular Cognition[complete]

TODO: We should reference Braitenbergs Vehicles here. Consider the chapter 5 stuff, definitely about wiring stuff into time. TODO: A cells is a networks PLUS a way to wire it up to world, via sensors and motors.

The last section began with Boolean regulatory networks. I show that these networks capture the causal structure of a regulatory program that mapped a sequence of inputs to a sequence of outputs. Mutating the program can change this response. And, by introducing successive mutations, we can gradually change a random program into one that produces some target response.

Our regulatory program is not a developmental program. It does not contain instructions for building anything. What the program does is respond to a stream of inputs etc. system that reacts to a constant stream of inputs. This kind of program is a controller, or a policy or, as I shall suggest here, a simple model of cognition.

An AND program encodes a simple model of behaviour: responding to a sequence of stimuli by generating a sequence of responses. The stimuli and responses are just abstract symbols A to Z. But we imagine that they correspond to real-world sensory inputs and motor outputs. In the case of gene regulation, these symbols correspond to the presence or absence of particular molecular signals that initiate or inhibit gene expression, and to the regulatory and structural proteins produced as a result.

We can bring these abstract symbols to life by wiring them to a simple agent, and embedding the agent in an environment. The stimuli are generated by the agent’s sensors as it moves about the environment, and the responses control the subsequent actions of the agent. We can think of this cell as a minimal agent, with the AND program encoding its cognition, and the sensorimotor system encoding its body and how it interacts with the world.

We will evolve our AND program so the cell can achieve a task in its environment. Importantly, the sensorimotor architecture remains fixed; only the cognitive wiring, controlled by the AND program, is subject to evolution.

The aim in this section to show that this simple architecture, inspired by gene regulation, can be evolved to respond adaptively to a changing environment. Our AND program effectively encodes the cognition of the cell.