Rosenblatt's large-scale replications helped refute molecular memory transfer, showing any effect was 'at most very small'

Frank Rosenblatt's rat brain-extract experiments (claim-rosenblatt-1966-tested-molecular-memory-transfer-in-rats) did not confirm the molecular theory of memory they set out to test. The surprising turn is that his careful, large-scale work cut against the fad rather than confirming it. Per Wikipedia, "Rosenblatt spent his last several years on this problem and showed convincingly that the initial reports of larger effects were wrong and that any memory transfer was at most very small."

The broader molecular-memory research program collapsed on unreliability — roughly half of rodent studies reported positive effects and half did not, the signature of an effect that is not real. Contemporary accounts put the peak of the craze at something on the order of two hundred teams and several hundred published reports (APA Monitor, Tier 3 — [unverified-quant — needs primary]). Rosenblatt's negative results were part of that deflation.

[unverified — this refutation claim is surprising and load-bearing but rests only on Tier 3 Wikipedia, below the Tier 1–2 sourcing floor for a surprising historical claim. Primary needed: Rosenblatt's own DTIC report "Studies of Memory Transfer in Rats" (AD0656488). Routed at [[question-verify-rosenblatt-dtic-memory-transfer-refutation]].]

The account of memory that survived is the distributed-network one Rosenblatt himself had seeded — claim-hopfield-1982-energy-function-from-spin-glass-physics, claim-dense-associative-memory-exponential-capacity. See moc-backpropagation-origins.