0. It might help if we stop “cognitizing” computation and symbols.
1. Computation is not a subset of AI.
2. AI (whether “symbolic” AI or “connectionist’ AI) is an application of computation to cogsci.
3. Computation is the manipulation of symbols based on formal rules (algorithms).
4. Symbols are objects or states whose physical “shape” is arbitrary in relation to what they can be used and interpreted as referring to.
5. An algorithm (executable physically as a Turing Machine) manipulates symbols based on their (arbitrary) shapes, not their interpretations (if any).
6. The algorithms of interest in computation are those that have at least one meaningful interpretation.
7. Examples of symbol shapes are numbers (1, 2, 3), words (one, two, three; onyx, tool, threnody), or any object or state that is used as a symbol by a Turing Machine that is executing an algorithm (symbol-manipulation rules).
8. Neither a sensorimotor feature of an object in the world, nor a sensorimotor feature-detector of a robot interacting with the world, is a symbol (except in the trivial sense that any arbitrary shape can be used as a symbol).
9. What sensorimotor features (which, unlike symbols, are not arbitrary in shape) and sensorimotor feature-detectors (whether “symbolic” or “connectionist”) might be good for is connecting symbols inside symbol systems (e.g., robots) to the outside objects that they can be interpreted as referring to.
10. If you are interpreting “symbol” in a wider sense than this formal, literal one, then you are closer to lit-crit than to cogsci.