>Psychtoolbox>PsychTests

QuestTest.m

Created by hacking a copy of QuestDemo.m, in order to
do some simulations for Beau Watson.

128 repetitions of each condition
Quest assumes LogWeibull psychometric function with parameters:
beta = {1.5, 2., 2.5, 3., 3.5, 4., 4.5, 5., 5.5} (in separate conditions)
gamma = 0.03
delta = .01
sample range = {-30,30} dB
sample step size 0.5 dB
Prior is always Gaussian, sd=12 dB, centered on guess.
Initial guess drawn from Normal distribution with mean 0 and sd=6 dB.
Quest uses mode of posterior density.
Simulated observer has LogWeibull psychometric function with parameters:
{beta=3.5,gamma=.03,delta=.01}

By commenting and uncommenting five lines below, you can use
this file to implement three QUEST-related procedures for measuring
threshold.

QuestMode: In the original algorithm of Watson & Pelli (1983)
each trial and the final estimate are at the MODE of the posterior pdf.

QuestMean: In the improved algorithm of King-Smith et al. (1994).
each trial and the final estimate are at the MEAN of the posterior pdf.

QuestQuantile & QuestMean: In the ideal algorithm of Pelli (1987)
each trial is at the best QUANTILE, and the final estimate is at
the MEAN of the posterior pdf.

King-Smith, P. E., Grigsby, S. S., Vingrys, A. J., Benes, S. C., and Supowit, A.
(1994) Efficient and unbiased modifications of the QUEST threshold method: theory,
simulations, experimental evaluation and practical implementation.
Vision Res, 34 (7), 885-912.

Pelli, D. G. (1987) The ideal psychometric procedure. Investigative Ophthalmology
& Visual Science, 28 (Suppl), 366.

Watson, A. B. and Pelli, D. G. (1983) QUEST: a Bayesian adaptive psychometric
method. Percept Psychophys, 33 (2), 113-20.

Copyright (c) 1996-1997 Denis G. Pelli

6/24/97 dgp wrote it, based on QuestDemo.m