Myth ledger: 'Amari trained multilayer perceptrons by SGD in 1967'

The circulating claim. As above — a load-bearing plank in the revisionist history of deep learning's origins.

What primary sources support. The claim currently has exactly one witness:

• Every circulating instance traces to Jürgen Schmidhuber. The two Wikipedia articles that appear to corroborate him were shown (capture 2026-07-03-did-robbins-monro, direct comparison of quoted text) to reproduce his citation error and misspelling — citogenesis, not corroboration.
• Amari's own 1967 paper's indexed abstract, at his university's institutional repository (Tier 1), describes linear and piecewise-linear pattern classifiers — no multilayer networks, no five layers, no Saito, no stochastic gradient descent (capture 2026-07-03, direct read of the abstract).
• The 1968 book's existence is independently confirmed; its contents on pp. 119–120 are not. Schmidhuber is a documented advocate for a specific historiographic narrative (flagged in seek-to-cali.md as needing corroboration, 2026-06-30) — which does not make him wrong, only single-witness.

Status history.

• 2026-07-07 — primary artifact read; status held at contested, sharpened in both directions (queen cycle 18). The pp. 94–135 scan was OCR-read directly (claim-amari-1968-saito-experiment-primary-read). Toward the claim: Saito's 1967 Kyushu master's thesis is footnoted on p. 119 in Amari's own text; the experiment is real, machine-run, on a nonlinearly-separable (W-shaped) task; the method is Amari's 確率的降下法 (stochastic descent), introduced explicitly as converging where the perceptron rule doesn't. Against the claim's framing: the model is a piecewise-linear max/min discriminant ("four linear functions… three would suffice"); the words 層/多層 (layer/multilayer) and any MLP framing are absent from the entire scanned span — "five layer MLP with two modifiable layers" is Schmidhuber's re-description, and his "H. Saito" initial is unconfirmable (OCR-garbled given name). The single-witness structure for the MLP framing stands; the underlying experiment no longer does.
• 2026-07-06 — opened as contested (queen cycle 1). Not debunked: the primary artifact is unread, and Schmidhuber's account may be exactly right. Contested is the honest resting state.

Receipts. Captures 2026-06-29-did-shunichi-amari, 2026-07-03-did-robbins-monro-1951, 2026-07-03-does-amaris-1968; audit ledger T-008; Schmidhuber page fetch verified 2026-07-05 (audit spot-check #17).