MATLAB Tutorial 7

These notes recap an introduction session to using PsychToolbox, a MATLAB toolbox commonly used in conducting experiments for stimulus display and recording responses. This first introduction includes a demo of drawing text and colours, teaching concepts of windows, rects and flips.

Initializing the PsychToolbox window

When running an experiment using PsychToolbox (PTB), there are a few initial lines of code that help set up stimulus display.

AssertOpenGL;       % 

screenID = max(Sreen(‘Screens’)); % Returns the screen number to display monitor Screen(‘Preference’,’SkipSyncTests’,1); % Set to 1 to skip any sync tests

[ptbWindow, winRect] = PsychImaging('OpenWindow', screenID, [], [], [], [], [], 6); 

[screenWidth, screenheight] = RectSize(winRect);
screenCentreX = round(screenWidth/2);
screenCentreY = round(screenHeight/2);
flipInterval = Screen('GetFlipInterval', ptbWindow);

Drawing text (DrawFormattedText)

In an experiment, text is often required when conducting an experiment, especially for instructions at the beginning, or when asking the participant for a response or informing the participant of a break. Firstly, let’s define the desired text to be shown:

text = ['Hello world!'];

To draw text, we simply use the DrawFormattedText function.