title: To characterize contrast detection, noise should be extended, not localized.
abstract: Adding noise to a stimulus is useful to characterize visual processing. To avoid triggering a processing strategy shift between the processing in low and high noise, Allard and Cavanagh (2011) recommended using noise that is extended as a function of all dimensions such as space, time, frequency and orientation. Contrariwise, to avoid cross-channel suppression affecting contrast detection, Baker and Meese (2012) suggested using noise that is localized as a function of all dimensions, namely "0D noise," which basically consists in randomly jittering the target contrast (and, for blank intervals or catch trials, jittering the contrast of an identical zero-contrast signal). Here we argue that contrast thresholds in extended noise are not contaminated by noise-induced cross-channel suppression because contrast gains affect signal and noise by the same proportion leaving the signal-to-noise ratio intact. We also review empirical findings showing that detecting a target in 0D noise involves a different processing strategy than detecting in absence of noise or in extended noise. Given that internal noise is extended as a function of all dimensions, we therefore recommend using external noise that is also extended as a function of all dimensions when assuming that the same processing strategy operates in low and high noise.
authors: INSERM, U968, Paris France ; Institut de la Vision, Sorbonne Universités - University Pierre and Marie Curie, UMR_S 968, Paris France ; CNRS, UMR_7210, Paris France.
authors: Rémy
authors: R
authors: Allard
authors: Visual Psychophysics and Perception Laboratory, Université de Montréal, Montréal, QC Canada ; NSERC-Essilor Industrial Research Chair, Montréal, QC Canada.
authors: Jocelyn
authors: J
authors: Faubert
keywords: 0D noise; contrast detection; contrast discrimination; extended noise; external noise paradigm