[vslist] (free) psychometric function software

[Felix Wichmann]

Announcing PSIGNIFIT: maximum-likelihood fitting and significance 
testing software for psychometric functions.

     http://www.bootstrap-software.org/psignifit

PSIGNIFIT is a multi-platform software tool for fitting sigmoidal 
psychometric functions to psychophysical data, taking into account 
possible "nuisance" parameters such as the observer's lapse rate, 
assessing goodness-of-fit by Monte-Carlo simulation, and providing 
confidence intervals via bootstrap methods.

Our methods were described in our Perception and Psychophysics papers:

Wichmann, F. A. & Hill, N. J. (2001a): The psychometric function I: 
fitting, sampling and goodness-of-fit. Perception and Psychophysics 
63(8), 1293-1313.

Wichmann, F. A. & Hill, N. J. (2001b): The psychometric function II: 
bootstrap based confidence intervals and sampling. Perception and 
Psychophysics 63(8), 1314-1329.

(N.B. in the papers we call our software "psychofit", but we have 
changed the name in order to avoid confusion with Lewis Harvey's 
software, also called "psychofit").

The software runs as a standalone command-line utility, but is easier to 
use when integrated with Matlab: a Matlab "mex-file" version of the 
engine is available, along with the PSIGNIFIT toolbox, a set of Matlab 
functions that can be used to view and assess the results.

With the latest version (2.5.4) we believe we have got out most of the 
significant bugs that were hindering the toolbox's cross-platform 
usefulness - confident enough, at least, to make this announcement at last.

The website also contains reports of some of our recent research into 
the factors affecting goodness-of-fit and confidence interval widths, 
and into the accuracy of these and other confidence interval methods.


Jeremy Hill, D.Phil.    http://www.kyb.tuebingen.mpg.de/~jez
Felix Wichmann, D.Phil. http://www.kyb.tuebingen.mpg.de/~felix

psignifit@bootstrap-software.org