Does a reward-prediction-error learning rule make the brain's score track the reward better?

EXPERIMENTS.md · lines 12676–12695

E202–E205 — the three fixes, one at a time, then together (2026-09-19 08:47; queued after E201 and E173c)

Correction to the E195/E195b tables above: the log's ± is the standard error over seeds (sd/√n), not the population sd; score_arms.py reports the ddof-1 sd. Baseline = E195b fly: AUC_Q 73.54 (s.e. 16.25, sd 23), 158 finds (sd 24), last-window finds 123 / 113, mean find depth −61.9; elitist 88.90 / 169.5 / last-window 147, 139 / depth −74.4 (seed mean). Code: branch fly-competitive (local search in Forager, imagination + history in FlyGenerator, prediction_error in mushroom.py, flags + diagnostics in stage_b; flags off reproduce E195b bit-for-bit by construction and by test). Predictions, each before its run:

• E202 local search (FORAGER_LOCAL_SEARCH=1): last-window finds ≥ 139 (elitist's floor) and distinct finds ≥ 170; AUC_Q within one seed-sd of elitist. If the last window does not move, the stall is not the walkers' memory and the anchor mechanism is wrong as built.
• E203 imagination (FORAGER_IMAGINE=4): mean find depth deeper by ≥ 5 meV than −61.9; finds unchanged within sd. Void if E201's score–reward correlation is < 0.2.
• E204 RPE (FORAGER_RPE=bennett): score–reward correlation up by ≥ 0.10 over E201's live arm; AUC_Q not worse.
• E205 all three vs elitist, 3 seeds: fly AUC_Q ≥ elitist − one seed-sd, finds ≥ elitist, depth within 5 meV of elitist's. If E205 fails after E202 passed, the pieces interfere and the combination is retuned one flag at a time, not all together.

EXPERIMENTS.md · lines 16329–16335

E204 RESULT — the Bennett rule misses its conjunctive bar by 0.01. runs/e204_rpe.log (finished 2026-09-20 03:00): fly AUC_Q 135.61 ± 17.52, 261 ± 36 distinct finds, best −95, score–reward ρ +0.73, last window 170. Bars (restated before E202 landed): ρ ≥ 0.74 and AUC_Q ≥ 134.7. AUC_Q met; ρ rose 0.09 from the 0.64 baseline against the 0.10 required. Falsified as written, by 0.01 on ρ. E205 then ran as "all three together", the form this log had called void, without E204 being scored first. Both predate the rung-1 estimator correction (2026-09-21), so neither is cited for the fly's rung-1 behaviour.