Hello, I have a code from a book to generate a psychophysical experiment. But I need to change it to present the stimuli in two screens instead of one. Can someone help?

The idea is to measure contrast sensitivity using a two-alternative forced-choice paradigm. The problem is that the way it is programmed, the stimuli are presented in pairs (the test stimulus and then the neuter stimulus or vice-versa in a random fashion) at the same screen. I need it to be presented in pairs but in two screens at the same time. Can someone help me with what modifications will I need to make? It needs Psychtoolbox to run. Thank you all very much!

The code is this:

     % Copyright (c) 2013, Massachusetts Institute of Technology
    % This program was presented in the book "Visual Psychophysics:
    % From Laboratory to Theory" by Zhong-Lin Lu and Barbara Dosher.
    % The book is available at http://mitpress.mit.edu/books/visual-psychophysics

    %%%Program ContrastPsychometricFunction.m

    function ContrastPsychometricFunction

    %%Display Setup Module
    % Define display parameters
    whichScreen = max(Screen('screens'));
    p.ScreenDistance = 30;  % in inches
    p.ScreenHeight = 15;    % in inches
    p.ScreenGamma = 2;  % from monitor calibration
    p.maxLuminance = 100; % from monitor calibration
    p.ScreenBackground = 0.5; 

    % Open the display window, set up lookup table, and hide the 
    % mouse cursor
    if exist('onCleanup', 'class'), oC_Obj = onCleanup(@()sca); end  
            % close any pre-existing PTB Screen window
    % Prepare setup of imaging pipeline for onscreen window. 
    PsychImaging('PrepareConfiguration'); % First step in starting
                                          % pipeline
    PsychImaging('AddTask', 'General',  'FloatingPoint32BitIfPossible');  
            % set up a 32-bit floatingpoint framebuffer
    PsychImaging('AddTask', 'General', 'NormalizedHighresColorRange');   
            % normalize the color range ([0, 1] corresponds 
            % to [min, max])
    PsychImaging('AddTask', 'General', 'EnablePseudoGrayOutput'); 
            % enable high gray level resolution output with 
            % bitstealing
    PsychImaging('AddTask','FinalFormatting',  'DisplayColorCorrection','SimpleGamma');  
            % setup Gamma correction method using simple power 
            % function for all color channels 
    [windowPtr p.ScreenRect] = PsychImaging('OpenWindow', whichScreen, p.ScreenBackground);  
            % Finishes the setup phase for imaging pipeline
            % creates an onscreen window, performs all remaining  
            % configuration steps
    PsychColorCorrection('SetEncodingGamma', windowPtr, 1/ p.ScreenGamma);  
    % set Gamma for all color channels
    HideCursor;  % Hide the mouse cursor 

    % Get frame rate and set screen font
    p.ScreenFrameRate = FrameRate(windowPtr); 
            % get current frame rate
    Screen('TextFont', windowPtr, 'Times'); 
            % set the font for the screen to Times
    Screen('TextSize', windowPtr, 24); % set the font size 
                                       % for the screen to 24

    %%Experimental Module

    % Specify general experimental parameters
    nContrast = 7;    % number of contrast levels in experiment
    repeats = 100;    % number of trials to repeat for each contrast
    nTrials = repeats * nContrast; 
                      % compute total number of trials
    p.randSeed = ClockRandSeed;     
                      % use clock to set random number generator
    keys = {'1' '2' 'esc'};  % specify response keys for the 
                      % two intervals and to break
    % Specify the stimulus
    p.stimSize = 6;   % image diameter in visual degree
    p.sf = 1;         % spatial frequency in cycle/degree
    conRange = [0.0025 0.04]; 
                      % lowest and highest tested contrasts
    p.stimDuration = 0.1;  % stimulus duration in seconds
    p.interval = 1;   % seconds between two intervals of a trial
    p.ISI = 0.5;      % seconds between trials

    % Compute stimulus parameters
    ppd = pi/180 * p.ScreenDistance / p.ScreenHeight * ...
          p.ScreenRect(4); 
                      % compute pixels per degree from 
                      % p.ScreenDistance and p.ScreenHeight
    m = round(p.stimSize * ppd /2) * 2; % stimulus size 
                                        % in pixels
    fixRect = CenterRect([0 0 1 1] * 8, p.ScreenRect);  
                      % define an 8 x 8 pixel fixation 
    % create another fixation stimulus of horizontal and 
    % vertical cross hairs outside the area of the sine wave
    % pattern. Crosshairs will be displayed during display
    % intervals

    fixLen = 32; % length of fixation in pixels
    fixXY = [[-1 0 0 1]*fixLen + [-1 -1 1 1 ] * m/2 + ...
          p.ScreenRect(3)/2  [1 1 1 1]*p.ScreenRect(3)/2; ...
          [1 1 1 1]*p.ScreenRect(4)/2 [-1 0 0 1] *fixLen + ...
          [-1 -1 1 1 ] * m/2 + p.ScreenRect(4)/2]; 

    p.contrasts = logspace(log10(conRange(1)), ...
               log10(conRange(2)), nContrast);
           % use logspace function to choose nContrast contrasts 
           % (7) at log intervals between the minimum and 
           % maximum specified contrasts
    sf = p.sf / ppd; % compute spatial frequency in 
                     % cycles per pixel
    tex = CreateProceduralSineGrating(windowPtr, m, m, [[1 1 1] ...
          *p.ScreenBackground 0], m/2, 0.5);
          % "CreateProceduralSineGrating" is a psychtoolbox 
          % function to create a procedural texture for drawing
          % sine grating stimulus patches on the GPU

    % Initialize a table to set up experimental conditions
    p.recLabel = {'trialIndex' 'contrastIndex' 'whichInterval' ...
             'respCorrect' 'respTime'};
          % labels the columns of the data recording array rec
    rec = nan(nTrials, length(p.recLabel)); 
          % matrix rec is initialized as an nTrials x 5 of NaN
    rec(:, 1) = 1 : nTrials;        
          % initialize trial numbers from 1 to nTrials
    contrastIndex = repmat(1 : nContrast, repeats, 1); 
          % use repmat to cycle thru contrast #s
    intervalIndex = ones(size(contrastIndex)) * 2; 
          % first set all trials to 2nd interval
    intervalIndex(1 : repeats / 2, :) = 1; 
          % change first half to 1
    [rec(:, 2) ind] = Shuffle(contrastIndex(:)); 
          % shuffle contrast indexes to randomize
    rec(:, 3) = intervalIndex(ind);  
          % shuffle interval indexes in the same order

    % Prioritize display to optimize display timing
    Priority(MaxPriority(windowPtr));

    % Start experiment with instructions
    str = sprintf('Press 1 or 2 for the first or second  interval.\n\nPress SPACE to start.');
    DrawFormattedText(windowPtr, str, 'center', 'center', 1);
          % Draw Instruction text string centered in window
    Screen('Flip', windowPtr);  
          % flip the text image into active buffer
    WaitTill('space'); % wait till space bar is pressed
    Screen('FillOval', windowPtr, 0, fixRect);   
          % create a black fixation dot
    Secs = Screen('Flip', windowPtr);   
          % flip the fixation image into active buffer
    p.start = datestr(now); % record start time

    % Run nTrials trials
    for i = 1 : nTrials
        con = p.contrasts(rec(i, 2));  
            % use contrast index from rec to set contrast 
            % for this trial
        flipSecs = Secs + p.ISI + [0 p.interval];  
             % define the start time of the two intervals

        for j = 1 : 2 % two intervals
            if rec(i, 3) == j 
                    % draw the grating in the interval defined 
                    % in rec(i,3) only
                Screen('DrawTexture', windowPtr, tex, [], [], ...
                      0, [], [], [], [], [], [180 sf con 0]);
            end     % draw the sine grating with phase 180, 
                    % spatial frequency, and contrast
            Screen('DrawLines', windowPtr, fixXY, 3, 0.3);  
                    % add the fixation crosshairs
            t0 = Screen('Flip', windowPtr, flipSecs(j)); 
                    % show the stimulus and return the time 
            Screen('Flip', windowPtr, t0 + p.stimDuration);
                    % turn off the stimulus by flipping to
                    % background image after p.stimDuration secs
        end

        Screen('FillOval', windowPtr, 0, fixRect); 
              % draw the smaller centered fixation
        Screen('Flip', windowPtr, t0 + 0.25 + p.stimDuration);
              % show small fixation briefly to cue the 
              % observer to respond with the interval

        [key Secs] = WaitTill(keys);   
              % wait for response, return key and response time
        if iscellstr(key), key = key{1}; end 
              % take the first response in case of multiple 
              % key presses
        if strcmp(key, 'esc'), break; end 
              % check if response is <escape> to stop experiment
        rec(i, 4 : 5) = [str2double(key)==rec(i, 3) Secs-t0]; 
              % record correctness and respTime
        if rec(i, 4), Beeper; end % beep if correct
    end

    p.finish = datestr(now); % record finish time
    save ContrastPsychometricFunction_rst.mat rec p;    
              % save the results

    %%System Reinstatement Module

    Priority(0);  % restore priority
    sca; % close window and textures, restore color lookup table

Answer 1

[Cedar Du]

Hi, do you have sample programs provided in this book? I have tried the website in the book, but I can't find the codes. Could you send the code to me or tell me the correct website? Thank you very much !!! (My email is [e-mail].)