Every trial comes with the same set of response categories. The example experiment has five of them. For each response category, you supply the area of the screen where a rectangle will be drawn. The whole screen measures from 0.0 (left) to 1.0 (right) and from 0.0 (bottom) to 1.0 (top). Thus, "0.2 0.3 0.7 0.8" means that a rectangle will be drawn somewhere in the top left quadrant of the screen. You also supply the text that will be drawn in this rectangle, for instance the text "h I d". After this you supply the font size for this text, for instance 40.
The second text that you supply for every response is a response key on the keyboard. In the above example this is "", i.e. the subject cannot press a key as a response. If you want the user to be able to press the "m" key instead of clicking in the "h I d" rectangle, the line in the experiment file would be:
0.2 0.3 0.7 0.8 "h I d" 40 "m" "i"
The third text that you supply for each rectangle is the response category as it will be reported by Praat to you when the user clicks it, e.g. the text "i". If you want Praat to ignore mouse clicks on this rectangle, specify an empty response category, i.e. "".
The border of the rectangles will be maroon, the background of the screen will be light grey. The colour of clickable rectangles will be yellow, that of non-clickable rectangles (those with empty category specifications) light grey.
You can have a picture instead of a text on a response button, by using \FI:
0.2 0.3 0.7 0.8 "\FIpictures/hello.jpg" 40 "m" "i"
In this example, the picture hello.jpg from the subdirectory pictures (i.e. a subdirectory of the directory where your experiment file is) will be drawn into the rectangle [0.2, 0.3] × [0.7, 0.8]. This currently (September 2011) works only on the Mac and Windows.
© ppgb, September 11, 2011