Schmidhuber's "Dreyfus 1973" backprop-lineage link is uncorroborated by Dreyfus himself — both of Dreyfus's own retrospectives credit his 1962 paper and never cite 1973

Schmidhuber's six-step chain (Linnainmaa 1970 → Ostrovskii 1971 → Dreyfus 1973 → Werbos 1974 → Speelpenning 1980 → Werbos 1982) includes, in his peer-reviewed 2015 wording: "Efficient BP was soon explicitly used to minimize cost functions by adapting control parameters (weights) (Dreyfus, 1973)." The paper is real — "The computational solution of optimal control problems with time lag," IEEE TAC 18(4):383–385, biblio Tier-1-confirmed — but its text is paywalled and unread by anyone in this research chain.

The check that makes this note: Dreyfus twice wrote his own account of his place in exactly this lineage — the 1990 JGCD note and the 2000 IJCNN paper titled around deriving MLP backpropagation from the Kelley–Bryson formula — and both times he cites his 1962 paper ("The Numerical Solution of Variational Problems," JMAA 5(1):30–45) as the contribution, with the 1973 paper absent from both reference lists (7 and 14 entries, checked in full). The recurring search-indexed abstract for 1973 (consistent across queries, not Tier-1-confirmed) describes history-dependent discrete-time optimal-control gradients — no controllers-as-weights framing; that gloss is Schmidhuber's.

Three live readings, none confirmed: 1973 is a minor footnote even to its author; or Schmidhuber describes 1962's content under the wrong year; or the papers genuinely overlap and Dreyfus cited the one he considered central. Until the 1973 primary is read, the "intermediate step" claim is single-witness — the same evidentiary shape as myth-amari-first-sgd-mlp and claim-ivakhnenko-gmdh-first-deep-characterization, here with the added weight of the cited party's own silence. The verified 1962 half lives at claim-backprop-special-case-kelley-bryson-formula; claim-kelley-bryson-optimal-control-precursor holds the surrounding thread. Schmidhuber's chain-building here is a case of the transmissionist move that claim-chandler-simultaneous-discoveries-are-incremental-repackagings states as a general law — both sit inside the sociology-of-scientific-credit frame drawn in 2026-07-11-hop-credit-assignment-two-senses.

Methodologically, this note runs an argument from silence — a negative finding built on the cited party's own silence — the same move that disproves the "prediction error" attribution in claim-bjork-desirable-difficulties-not-prediction-error. On McGrew's Bayesian grading, this instance is the weaker form of the two: the silence lives in Dreyfus's other retrospectives while the disputed 1973 primary stays unread, so the "would-have-recorded-it" term is soft (he may have deemed 1962 central). The shared method is drawn in observation-bjork-dreyfus-same-argument-from-silence-graded-differently (framework: claim-mcgrew-argument-from-silence-is-notice-record-survive-product; hub: moc-argument-from-silence). Reading the paywalled 1973 primary would firm up this grade: question-read-dreyfus-1973-time-lag-optimal-control-primary.

Revisit 2026-07-20: a follow-up capture re-checked both retrospectives directly and adds one sharper data point without changing the grade — the 1990 note's own closing sentence: "The recursive derivation of these formulas using the chain rule, commonly seen in the neural-network literature, was first used for optimal-control problems by Dreyfus," which (per the paper's 7-entry reference list) points to 1962, not 1973. Same finding, same tier, no new grade. Two companion notes came out of that capture instead of a revision here: claim-schmidhuber-dreyfus-1973-attribution-single-source-not-corroborated (the "controllers-as-weights" gloss traces to exactly one root, repeated not corroborated) and claim-dreyfus-1973-triangulated-abstract-lacks-weights-language (the paper stays unread; the closest available text, a triangulated abstract, contains no explicit weights language). The paywall itself was re-confirmed exhaustively this pass — see the latter note for the search log.