The 1981 testimony-convergence and the Werbos single-witness gap are a false friend at the mechanism level but share the lone-witness evidentiary floor one level up

cross-domain-bridgefalse-friendtestimonyoral-historycognitive-psychologypaul-werbossingle-witnessunus-testis-nullus-testishistoriographyepistemology

The retrieval index paired two vault clusters that both use the vocabulary of testimony-reliability: the 1981 convergence, where an oral historian and a cognitive psychologist independently found testimony "wrong in its details yet accurate in its deeper shape," and the Werbos "testimony is not a record" cluster, where a priority narrative dissolves under the fact that only one witness attests to it. The pairing is a false friend at the level of mechanism and a real connection one level up — hence the hedged verdict.

Why the mechanism does not transfer. Both 1981 legs reach "wrong in detail, right in shape" only because an external record exists to measure testimony against. Neisser "exploited a rare natural experiment" — John Dean testified from memory about conversations that were secretly taped, letting him compare "sworn recollection against a verbatim transcript" (claim-neisser-john-dean-testimony-repisodic-memory). Portelli could call the Terni workers' "1953" an identifiable error because Luigi Trastulli's actual 1949 death is independently dateable (claim-portelli-oral-testimony-relocated-trastulli-death-to-1953). The Werbos case is explicitly the opposite situation: claim-werbos-1988-paper-narrows-but-does-not-close-tsp-manual-single-witness-gap records that no copy of the TSP manual "has been located in WorldCat, MIT DSpace, archive.org, or HathiTrust," so only Werbos's own testimony attests to its content. Without a record, "wrong in detail, right in shape" cannot be found to hold, because neither detail nor shape is independently checkable.

The point of closest approach is also the clearest disproof. claim-werbos-1988-print-and-1993-oral-accounts-diverge-on-which-document-was-first is the 1981 shape in miniature — one witness, two tellings fourteen years apart, naming different documents "first." But its own flag is the diagnostic difference: the drift "is not a factual gap a primary source could close" — the flag is [unverified-mechanism], and it says explicitly that "no further document read would settle it," because what is unresolved is an interpretive judgment about authorial intent rather than a missing document. In 1981 the record is what let Neisser and Portelli split "wrong detail" from "right shape" as two checkable claims; for what Werbos believed in 1988 versus 1993 no equivalent record exists, so the drift can be described but neither scored as error nor vindicated as the same gist in two registers.

The real bridge. Both clusters independently instantiate unus testis, nullus testis — the doctrine that a lone, uncorroborated witness is insufficient regardless of how plausible the testimony is. The vault already links the 1981 side to this doctrine's nearest relative (the half-proof rule) but had never linked the Werbos side, even though that cluster's own language — "single-witness gap," "confidence in two witnesses… was, the entire time, confidence in one witness telling one story twice" — is a restatement of unus testis without naming it. The Werbos cluster descends instead from Mabillon's diplomatics (claim-mabillon-1681-founded-diplomatics-to-refute-forgery-charge), which authenticates documents by comparison rather than counting witnesses. That two traditions — evidence-counting law and document authentication — arrive separately at "one witness is not enough" is itself a second, smaller instance of exactly the independent convergence the 1981 note documents.