Version 3.0.19 17 February 2023

The Psychophysics Toolbox is a collection of Octave and Matlab functions
that extend the language to give you exquisite control of your computer
to test observers with research-grade dynamic stimuli. Parts of it are
also used as critical parts of Python toolkits like PsychoPy.

Every Psychtoolbox function has its own documentation available through
the Matlab HELP command, and, in the case of MEX files, through the
function itself. We’ve tried hard to make these individual bits of
documentation clear, accurate, and complete. We’re grateful to receive

We’ve mostly followed Mathworks’s help-text conventions, but note that in
our help text we designate optional arguments to function calls by
embracing them with square brackets. You’re not meant to include these
brackets when you actually call the function. For example, “help Snd
will tell you this:

err = Snd(command,[sig],[rate])

meaning that the “command” argument is required and the “sig” and “rate”
arguments are optional. A typical call to Snd looks like this:

Snd(‘Play’, mysoundsignal)

The most important and generally useful functions, especially Screen, are
in PsychBasic. The PsychDemos will show you how to do useful things in
Matlab with the Psychtoolbox. Try these:

help PsychDemos
help PsychBasic
help Screen
Screen OpenWindow?

The folder PsychDocumentation contains bits of documentation about
technical implementation details, how to solve specific tasks and how to
troubleshoot common problems.

To read more, look at the “intro” and “docs” pages at the web site. The
web site also has advice about getting help, the Psychtoolbox forum, and
the latest information about bugs and new releases:

Peter Scarfe has written a large set of nice and beginner friendly
Psychtoolbox tutorial scripts.

You can find them at

If you want to acknowledge use of this software when you publish your
research, you might say something like this, “We wrote our experiments in
Matlab, using the Psychophysics Toolbox extensions (Kleiner et al, 2007)”

Kleiner M, Brainard D, Pelli D, 2007, “What’s new in Psychtoolbox-3?”
Perception 36 ECVP Abstract Supplement.

Folders and their contents:

PsychAlpha - Under development. Experimental, risky, undocumented.
PsychAlphaBlending - OpenGL alpha-channel blending utilities and constants.
PsychBasic - Basic support routines for psychophysics.
PsychCal - Calibrate your video monitors.
PsychCalDemoData - Demo calibration data.
PsychColorimetric - Colorimetric calculations.
PsychColorimetricData - Standard colorimetric data.
PsychContributed - Contributed programs.
PsychDemos - Show how to use the Psychtoolbox.
PsychDocumentation - Documentation about specific topics.
PsychFiles - Process text files.
PsychGamma - Fit monitor gamma functions.
PsychGLImageProcessing - Built-in image processing via graphics hardware.
PsychGPGPU - General purpose accelerated computing on GPUs.
PsychHardware - Interface to plug-in hardware.
PsychInitialize - Initialize and deinitialize MATLAB
PsychMatlabTests - Document the few bugs in Matlab 5.2.1.
PsychObsolete - Obsolete routines, still present for compatibility.
PsychOpenGL - Routines for low-level access to OpenGL 3D graphics.
Psychometric - Psychometric function fitting.
PsychOneliners - Trivial, but handy, functions.
PsychOptics - Optics calculations, mostly for human optics.
PsychPriority - Priority and Rush. (formerly within PsychBasic))
PsychProbability - Probability and statistics.
PsychRadiometric - Radiometric/photometric calculations and conversions.
PsychRects - Manipulate rectangles for drawing.
PsychSignal - Signal processing and math routines.
PsychSound - Sound input and output routines.
PsychStairCase - Adaptive staircase procedure.
PsychTests - Evaluate performance of software and hardware.
PsychVideoCapture - Functions for realtime video capture.
Quest - Threshold estimation procedure.


You can now financially contribute to Psychtoolbox sustainability, upkeep
and continued improvement by buying a “Psychtoolbox Support Membership”, which
also includes some paid support for questions regarding its use, or issues
you may have with it. We also offer paid feature development and other
useful commercial services.

Please type ‘PsychPaidSupportAndServices’ to learn more.

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