CORNELL
U N I V E R S I T Y 		17Food Science 430
Wine is chemistry, biology and psychology!

Calendar

Primer
Psychophysics

Reading: Jackson pp 564-590
Psychophysics
by Harry T. Lawless

PSYCHOPHYSICAL RELATIONSHIPS

    S = sensation intensity
    I = Physical stimulus intensity
    R = response or rating

  1. Weber's Law

    DI / I = K, where K is a constant percent change

    where DI = change in intensity needed to create a just-noticeable-difference (JND), and I is the level of the comparison or standard.

  2. Fechner's Law

    S = k1 log ( I ) + k2

    Fits category scales well and functions generated by indirect means, e.g. from accumulation of difference thresholds.

  3. Steven's Power Functions

    S = k2 ( I ) n

    or log ( S ) = n log ( I ) + log k2

    Fits magnitude estimation data well, and other open-ended scales.

  FS430 Revised 3.7.01