Information about what?

In a previous post, I pointed out that the word “information” is almost always used in neuroscience in the sense of information theory, and this is a very restricted notion of information that leads to dualism in many situations. There is another way to look at this issue, which is to ask the question: information about what?

In discussions of neural information or “codes”, there are always three elements involved: 1) what carries the information, e.g. neural electrical activity, 2) what the information is about (e.g. the orientation of a bar), 3) the correspondence between the first two elements. If dualism is rejected, then all the information an organism ever gets from the world must come from its own senses (and the effect of actions on them). Therefore, if one speaks of information for the organism, as opposed to information for an external observer, then the key point to consider is that the information should be about something intrinsic to the organism. For example, it should not be about an abstract parameter of an experimental protocol.

So what kind of information are we left with? For example, there may be information in one sensory signal about another sensory signal, in the sense that one can be (partially) predicted from the other. Or there can be information in a sensory signal about the future signal. This is equivalent to saying that the signals follow some law, a theme developed for example by Gibson (invariant structure) and O’Regan (sensorimotor contingency).

One might think that this conception of information would imply that we can’t know much about the world. But this is not true at all, because there is knowledge about the world coming from the interaction of the organism with the world. Consider space for example. A century ago, Poincaré noted that space, with its topology and structure, can be entirely defined by the effect of our own movements on our senses. To simplify, assume that the head and eyes are fixed in our body and we can move only by translations, although with possibly complex movements. We can go from point A to point B through some movements. Points A and B differ by the visual inputs. Movements act on the set of points (=visual inputs) as a group action that has the structure of a two-dimensional Euclidian space (for example, for each movement there is an opposite movement that takes you back to the previous point, combinations of movements are commutative, etc). This defines space as a two-dimensional affine space. In fact, Poincaré (and also Einstein) went further and noted that space as we know it is necessarily defined with respect to an observer. For example, we can define absolute Cartesian coordinates for space, but the reference point is arbitrary, only relative statements are actually meaningful.

In summary, it is not so much that the concept of information or code is completely irrelevant in itself. The issues arise when one speaks of codes about something external to the organism. In the end, this is nothing else than a modern version of dualism (as Dennett pointed out with his “Cartesian theater”). Rejecting dualism implies that any information relevant to an organism must be about something that the organism can do or observe, not about what an external observer can define.

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