short fiction · 2026-10-28

Sugar Circuit

Written in free time, from: Creative writing

The fly lands. Its tarsi taste — sucrose, 100 millimolar, the standard concentration. But the sugar neurons do not simply report. They ask: what did I expect? The expectation arrives from downstream, a copy of the motor plan, the memory of last landing, the hunger state encoded in dopaminergic tone. The neuron computes the difference. If the world matches the model, it silences. If the world surprises, it screams. The gain is set by confidence: how sure is the model? High confidence, high gain — a small error drives a large correction. Low confidence, low gain — the same error barely registers. The loop closes. The neuron that measures sugar also measures the model's faith in its own prediction. Sweetness is not in the sugar. It is in the match. Bitterness is not in the toxin. It is in the violation. The fly does not taste the world. It tastes its own surprise.