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Recording responses


I am trying to design an experiment whereby participants will be shown a series of stimuli ((target phase) images in one condition, and words in another)). After seeing the stimuli, participants will be given an interference task. They will then be presented with a further set of stimuli (test phase), containing a handful of previously shown stimuli, amongst various foils. All stimuli shown shall ideally be randomised.
During the test phase, participants are requested to indicate whether they have seen any one stimulus in the previous phase (by pressing Z or M on their keyboard).
I have little - to no knowledge of Python or coding, how do I get OS to record correct responses?

Many thanks,


  • Hi Rob,

    Have you followed the beginner's tutorial? Defining correct responses is part of it. Basically, in the loop table of the test phase, you can set what trial type you have (foil vs. memory) and depending on that you can set a correct_response variable.

    Does that make sense?


  • Hello,

    That makes sense, thank you.

    Might I also ask how you go about assigning random participants so that half view a certain message, and half do not? As far as I am aware you need to edit the 'run if' section, however I am unsure how to re-write python so that it only runs to one of two groups

  • Hi Rob,

    you can use the variable `var.subject_parity` for that purpose. It will have the values odd and even, depending on the participant number.

    Does that help?


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