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keyboard response 1 key only

edited May 2016 in OpenSesame

In experiment with 2 stimuli I have 2 possibility responses (i.e. "a" or "b" keys). In my practice I create a table with "letter" (i.e. "H" and "X") and "correct_response ("a" "b").
I would like one possible response per stimuli only. But when X appears I can use "a" or "b". In fact I would like that a participant may not be able make mistakes.
Do you have idea(s)?
Thanks very much,


  • edited 12:13PM

    Hi Guillqume,

    You'll need to place 2 keyboard_response items in your trial sequence for this. As allowed response, you indicate only 'a' and only 'b' respectively. Clicking on the trial sequence item, you can indicate a run-if statement. Here you indicate run-if [letter] = "H" and [letter] = "X" for the two respective keyboard items.

    Hope this helps.



  • edited 12:13PM

    Also, beware that participants may find out about this and just press both buttons simultaneously every trial, to get super fast RT's and no errors. But if you only do it like this in the practice phase it's fine I guess.


  • edited 12:13PM

    Great !
    Thank you Josh.

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