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reaction time counted from onset or offset

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  • reaction time counted from onset or offset

    Dear members,
    I have submitted a manuscript on Stroop interference (e.g. BLUE written in green colour) to a journal and one of the reviewers was surprised about the long reaction time latencies I found. The experiment involved an old Superlab program which as an aside I am very happy with. Actually, I now realize that I do not have a clue whether Superlab (a) reports reaction times from the onset **or** the offset of a target and (b) which information I should present in a paper. Example: Let's say I have a target displayed for 500ms and Superlab reveals mean reaction times of 800ms. Does this mean the real RT is 300 or 800 ms from offset of the target and should I present RT including stimulus duration.

    I would be happy for a reply.

    Kind regards, Steffen

  • #2
    Hi Steffen,

    In SuperLab 1.7x and 2.0, the RT timer is reset at the onset of each event in a trial. If you'd like, please post the experiment and a sample data file and I'll take a look at them. Or you can email them to me directly if you'd rather not post them publicly.

    Hisham.

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    • #3
      Hi Steffen,

      I got your experiment. Alas, I wasn't able to open the SuperLab 1.7x experiment because I'm currently on travel and have my Intel-based MacBook which cannot run SuperLab 1.75. We only have one machine left, I think, at the office that can run SuperLab 1.75.

      However, I took a look at the data files. Overall they look just fine to me. Every once in a while, there is an RT that takes longer, i.e. about 3-4 times the average. But they are a very small minority and can easily be attributed, e.g., to participant fatigue.

      IMO, I think that it would make sense to eliminate a few records. For example, you left the "instructions" RT, which is about 66+ seconds in two of the three files that you sent me. This alone will distort the mean greatly. In another file, you have an RT of 27150 milliseconds, which seems like the perhaps the participant had stopped to ask a question.

      But overall, the data looks fine to me.

      Cheers,

      Hisham.

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