Perspectives
Where the central processor Analogy Breaks
A CPU executes explicit instruction sets on a deliberately designed architecture. Brains grow, metabolize, rewire, learn, recover and degrade through physical changes to the…
Calling the brain a central processor is useful for about five minutes. The comparison can expose structure that ordinary language hides. The problem begins when the comparison stops behaving like a tool and starts behaving like a claim about what the thing literally is.
Distributed processing, feedback, prediction and state are often better engineering metaphors than a single CPU because brain activity is massively parallel and recurrent.
What the metaphor gets right
Distributed processing, feedback, prediction and state are often better engineering metaphors than a single CPU because brain activity is massively parallel and recurrent.
This is why engineering metaphors are so attractive. They compress a complicated relationship into something we can manipulate mentally. In the best case, the metaphor produces predictions and sharper questions.
What it smuggles in
A CPU executes explicit instruction sets on a deliberately designed architecture. Brains grow, metabolize, rewire, learn, recover and degrade through physical changes to the network.
Engineering words often carry hidden assumptions: a designer, a specification, modular ownership, explicit goals, a stable machine underneath the program. Those assumptions must be tested rather than inherited.
Return to the physical story
The brain is a living network of neurons and glia embedded in a body. Its activity depends on sensory input, internal physiology, past learning, neuromodulation and continuous interaction with muscles and organs.
Once the mechanism is back in view, the analogy can be kept on a short leash. We can state which relation is genuinely similar and which difference would make the analogy generate a wrong prediction.
My three tests for a metaphor
- What mechanism does this comparison help me see?
- Which engineering assumption does the natural system not share?
- What would I predict incorrectly if I took the comparison literally?
The third test is the most important. An analogy that cannot fail is decoration, not explanation.
Beyond the borrowed language
Cajal's neuron doctrine helped reveal individual nerve cells; electrophysiology and imaging later exposed brain dynamics across many scales.
The brain is matter that can build models of other things and, apparently, models of itself.
What does a physical network need to model before a point of view appears?
A good metaphor should eventually make itself less necessary. It gets us close enough to the real system that we can see where the scaffolding ends.
Reading trail
These links are starting points for the scientific and historical ideas. The systems interpretation, analogies and conclusions here are my own.