The constancy method is a method for determining the threshold for certain stimuli in human subjects . It was first described in 1860 by Gustav Theodor Fechner as the method of correct and incorrect cases .
The test person is very often stimulated in random order with stimuli of the same type of different strengths, with both clearly subliminal and clearly supra-threshold stimuli. The respondent always answers “Yes” when he thinks he has perceived a stimulus. Then the detection probability (proportion of “yes” answers) is plotted against the stimulus strength.
This method gives a psychometric function. This is sigmoid because clearly subliminal stimuli are never recognized and clearly supra-threshold stimuli are always recognized. The absolute threshold for this stimulus is - by convention - the stimulus strength at which recognition took place in 50 percent of cases ( point of subjective equality , PSE).
- Manuel Kühner, Heiner Bubb, Klaus Bengler and Jörg Wild: Adaptive methods in psychophysics - efficient determination of absolute and difference thresholds . In: Ergonomics up-to-date . Issue 13. 2012. ( direct link )
- Manuel Kühner: Haptic distinguishability of mechanical parameters in rotary control elements , dissertation, Technical University of Munich, 2014 ( Link )
- Jürgen Bortz, Christof Schuster: Statistics for human and social scientists . Springer Berlin Heidelberg; Edition: 7th, completely revised. u. updated edition (August 16, 2010). ISBN 978-3642127694 . Page 159
- Jürgen Bortz, Christof Schuster: Statistics for human and social scientists . Springer Berlin Heidelberg; Edition: 7th, completely revised. u. updated edition (August 16, 2010). ISBN 978-3642127694 . Page 163
- Psychophysical methods - presentation of various methods
- Psychophysics - project page of a dissertation with background information on psychophysical methods such as the staircase method, classic methods such as the constancy method and the boundary and manufacturing process can be found in the dissertation itself.