Why use noise?

Denis G. Pelli, Bart Farell

Research output: Contribution to journalArticlepeer-review


Measuring the dependence of visual sensitivity on parameters of the visual stimulus is a mainstay of vision science. However, it is not widely appreciated that visual sensitivity is a product of two factors that are each invariant with respect to many properties of the stimulus and task. By estimating these two factors, one can isolate visual processes more easily than by using sensitivity measures alone. The underlying idea is that noise limits all forms of communication, including vision. As an empirical matter, it is often useful to measure the human observer’s threshold with and without a noise background added to the display, to disentangle the observer’s ability from the observer’s intrinsic noise. And when we know how much noise there is, it is often useful to calculate ideal performance of the task at hand, as a benchmark for human performance. This strips away the intrinsic difficulty of the task to reveal a pure measure of human ability. Here we show how to do the factoring of sensitivity into efficiency and equivalent noise, and we document the invariances of the two factors.

Original languageEnglish (US)
Pages (from-to)647-653
Number of pages7
JournalJournal of the Optical Society of America A: Optics and Image Science, and Vision
Issue number3
StatePublished - Mar 1999

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Computer Vision and Pattern Recognition


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