Barlow's 1961 efficient-coding hypothesis holds that sensory neurons recode input to strip statistical redundancy

Horace Barlow's efficient-coding (or redundancy-reduction) hypothesis, put forward in his 1961 chapter "Possible Principles Underlying the Transformations of Sensory Messages," proposes that early sensory systems are shaped to recode their input into a more economical form by removing the statistical redundancy natural stimuli carry. Because the visual world is highly correlated across space and time, a raw sensory message contains far more bits than the information it conveys, and Barlow frames redundancy reduction as the operation relays perform on it. This core is now confirmed against the 1961 primary itself — read in full, with Barlow stating it in his own words (claim-barlow-1961-primary-states-redundancy-reduction-in-his-own-words) — rather than resting on secondary attribution.

Two elaborations often attached to "Barlow 1961" are not in the 1961 chapter and are corrected here. The factorial code label — a representation whose channels are statistically independent — does not appear in the text (the word "factorial" occurs once, as arithmetic in a toy example); it is a later accretion onto Barlow's name (see claim-barlow-1961-does-not-name-factorial-code). Likewise, center-surround receptive fields as the redundancy-removing mechanism — few spikes for uniform patches, strong response to local contrast — are nowhere in the chapter, which stays deliberately at the level of abstract information-theoretic "operations," not physiology (see claim-barlow-1961-does-not-invoke-center-surround-as-the-redundancy-reducing-mechanism). Both are plausibly true of Barlow's broader corpus, but they are not statements this chapter makes.

The hypothesis is the theoretical "why" beneath perceptual fading: unchanging input is erased because it is redundant, and the eye must move to keep generating non-redundant signal — see claim-fixational-eye-movements-prevent-perceptual-fading. It also names a modern descendant: the 2021 self-supervised loss in claim-barlow-twins-loss-minimizes-embedding-redundancy is called Barlow Twins precisely "owing to neuroscientist H. Barlow's redundancy-reduction principle," decorrelating embedding components in the same spirit. The "discard the congruent, encode the change" shape connects it to claim-cognitive-conflict-prerequisite-for-restructuring and to the prediction-error account in claim-p3-indexes-prediction-error-schema-updating.