Limits of visual communication: The effect of signal-to-noise ratio on the intelligibility of American Sign Language

M. Pavel, George Sperling, Thomas Riedl, August Vanderbeek

Research output: Contribution to journalArticle

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To determine the limits of human observers’ ability to identify visually presented American Sign Language (ASL), the contrast s and the amount of additive noise n in dynamic ASL images were varied independently. Contrast was tested over a 4:1 range; the rms signal-to-noise ratios (s/n) investigated were s/n = 1/4, 1/2, 1, and ∞ (which is used to designate the original, uncontaminated images). Fourteen deaf subjects were tested with an intelligibility test composed of 85 isolated ASL signs, each 2–3 sec in length. For these ASL signs (64 × 96 pixels, 30 frames/sec), subjects’ performance asymptotes between s/n = 0.5 and 1.0; further increases in s/n do not improve intelligibility. Intelligibility was found to depend only on s/n and not on contrast. A formulation in terms of logistic functions was proposed to derive intelligibility of ASL signs from s/n, sign familiarity, and sign difficulty. Familiarity (ignorance) is represented by additive signal-correlated noise; it represents the likelihood of a subject’s knowing a particular ASL sign, and it adds to s/n. Difficulty is represented by a multiplicative difficulty coefficient; it represents the perceptual vulnerability of an ASL sign to noise and it adds to log(s/n).

Original languageEnglish (US)
Pages (from-to)2355-2365
Number of pages11
JournalJournal of the Optical Society of America A: Optics and Image Science, and Vision
Issue number12
StatePublished - Dec 4 1987


ASJC Scopus subject areas

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

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