/usr/share/psychtoolbox-3/PsychTests/QuestTest.m is in psychtoolbox-3-common 3.0.11.20140816.dfsg1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 | % 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
fprintf('beta mean sd reps\n')
reps=64;
for beta = [1.5:.5:5.5]
estimate=1:reps;
for i=1:reps
gamma = 0.03;
delta = .01;
tGuess=randn*6/20;
tGuessSd=12/20;
range = 3;
grain=0.5/20;
pThreshold=0.6370;
tActual=0;
trialsDesired=64;
wrongRight=char('wrong','right');
q=QuestCreate(tGuess,tGuessSd,pThreshold,beta,delta,gamma,grain,range);
qObserver=QuestCreate(tActual,tGuessSd,pThreshold,3.5,delta,gamma,grain,range);
%fprintf('Quest estimate of thresh after initialization is %g\n',QuestMean(q));
%fprintf('Initial value was %g\n',tGuess);
%fprintf('Quest estimate of sd after initialization is %g\n',QuestSd(q));
%fprintf('Initial value was %g\n',tGuessSd);
for k=1:trialsDesired
tTest=QuestMode(q); % 0.03 s
response=QuestSimulate(qObserver,tTest,tActual); % 0.10 s
q=QuestUpdate(q,tTest,response); % 0.10 s
end
t=QuestMode(q);
%fprintf('%4.1f\t%+6.3f\n',beta,t);
estimate(i)=t;
end
fprintf('%4.1f\t%+6.3f\t%5.3f\t%d\n',beta,mean(estimate),std(estimate),length(estimate));
end
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