Ask participants for button press?

Hi guys,

I programmed an experiment and I am rather new to Psychtoolbox and Matlab and one thing is not quite working. I began to try to code the sequence by myself and then I just copied a piece of code from the psychtoolbox tutorial page and it is still not working. That's why assume there might be another problem I haven`t thought about?

I display two pictures in my experiment and I want participants to answer with the left respectively right arrow key before the next pair of pictures is shown.

Here is what I did:

leftKey=KbName('LeftArrow');
rightKey=KbName('RightArrow');
escape=KbName('ESCAPE');
resp==true;

while resp==true;
   [keyIsDown,secs,keyCode]=KbCheck;
   if keyCode (escapeKey)
      sca;
      return
   elseif keyCode(leftKey)
      response=1;
      resp=false;
   elseif keyCode(rightKey)
      response=2;
      resp=false
   end
end
Screen('Flip',window)

This works to escape but it does not register any answers :(.

I have also tried

while(~keyCode(leftKey))
    [keyisDown,sec,keyCode]=KbCheck;
end

which unforuntnately does not switch to the next screen either.

And just to check whether left button presses are registered in any way, I wrote:

while (~keyCode(leftKey))
    [keyisDown,sec,keyCode]=KbCheck;
end

... a left button press doesn't let me quit the loop either...

THANKS!!!!

[Geoff Hayes]

Laurie - your comments indicate that the first set of code works fine for when the user presses the escape key but not when he or she presses the left or right arrow keys. Is this correct? If so, then put a breakpoint at the line

 if keyCode (escapeKey)

and run your software. Press the left arrow key and check to see which element of keyCode is true. Does this match with

 leftKey=KbName('LeftArrow');

[Laurie Gerstenberger]

Yes,awesome! It worked. Thank you so much!

[Mihaela Duta]

I would also suggest you add as a standard at the top of your experiment scripts the command

KbName('UnifyKeyNames');

As the help for KbName function states, this will ensure that at least the names of special keys (like cursor keys, function keys and such) will be shared between operating systems.

When getting inspiration from other people's scripts, or when migrating your own scripts to a computer with a different operating system that the one originally used to debelop the scripts, you may encounter issues with key name mapping. The above command will avoid such issues.