Interactions

Someday I want to write a PHD-thesis on the concept of interaction. Just for starters, let's make a quick inventory of types of interaction, based on the number of active agents involved.

1. No active agents involved
In physical systems with nog active agents, like human beings, other animals, or artificial intelligent systems involved, there is physical interaction based on the flux of energy between two physical sub-systems. For instance, when a billiartball hits another billiartball, energy is moved from one ball to the other, and the two balls thereby influence one another's behavior. Or when two chemical substances meet, there might be a chemical reaction, leading to a new stable state, in which some or all of the chemical substances have been combined, or falled apart, etc.. It is interaction of stuff with stuff. Stuff (or energy, which is the same) is being exchanged, moved about, all involved systems change state, i.e. they undergo some behavioral change, and new stabilities arise as a result of that.

2. Two active agents involved.
Interaction between two agents is different from interaction between two 'substances' since the interaction does not take place in the form of energy flow but in the form of *information* flow. Another word for this kind of interaction is "communication". It means that two active agents continously *interpret* the physical changes as they are received on their sensors, coming from the other agent, *as signals*, with an associated *meaning*. The level at which the interaction has meaning is on this informational level alone, the physical level is not interesting just so long as it exists, otherwise the information channel could not be physically realised, which would render communication impossible. But, where in case of the billiartballs the physical structure and energy processes in the system determined the nature of the interaction, in the case of two active agents interacting the nature of the interaction is determined not by the physical structure and energy flux that realises this interaction, but by the *meaning* of the communicative message that is send from one agent to the other.

Of course, one could envision a situation in which two agents bump into each other, as a purely physical accident. But in this case, I argue, the agent's should not be conceived of as active agents, but as passive physical systems only.

3. One active agent involved.
This is the most difficult case because it embodies a blend of the two definitions of interaction above. It is the case where a human agent 'interacts' with his (her) environment. Such kind of interaction is of central concern to cognitive science. The usual question there is: how does the active agent come to understand the (physical) environment or, how does the active agent know how to act appropriately in it? (which basically amounts to the same thing depending on your philosophy). Sensors on the active agent register input, the agent generates behavioral output on its 'actors' (body movement), which in turn leads to new sensory input, and so on. This perception-action cycle, which evolves over time, defines "the interaction". The interaction can be 'functional' with respect to the internal goals of the agent, or, likewise, it can be 'appropriate given the environmental situation. Biologically, one often speaks of 'adaptive' behavior, which relates to underlying evolutionary forces.

Now, what I want to discuss, in a later blog, is how one can mix physical interaction with communication, because I have a feeling that type 3 above contains some theoretical problems...