The role of psychophysics in phytopathology: The Weber-Fechner law revisited

Forrest W. Nutter, Paul D. Esker

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

The accuracy and precision of disease severity assessment data might be improved if there was a better understanding of how the laws of psychophysics actually relate to the theory and practice of phytopathometry. In this regard, we utilized a classical method developed in the field of psychophysics (the method of comparison stimuli) to test Horsfall and Barratt's claim that raters cannot accurately discriminate disease severity levels between 25% and 50% because, according to the Weber-Fechner law, visual acuity is proportional to the logarithm of the intensity of the stimulus. We show for two pathosystems, wheat leaf rust and grapevine downy mildew, that raters can accurately discriminate disease severity levels between 25% and 50%, and that although Weber's law appears to hold true, Fechner's law does not. Furthermore, based upon our results, the relationship between actual (true) disease severity (X) and disease severity estimated by raters (F) is linear, not logarithmic as proposed by Horsfall and Barratt.

Original languageEnglish (US)
Pages (from-to)199-213
Number of pages15
JournalEuropean Journal of Plant Pathology
Volume114
Issue number2
DOIs
StatePublished - Feb 2006

All Science Journal Classification (ASJC) codes

  • Agronomy and Crop Science
  • Plant Science
  • Horticulture

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