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Response window longer than stimuli presentation time

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  • Response window longer than stimuli presentation time

    Hi,

    This is probably quite simple but I can't see how present a stimulus for 500ms but allow a response window of 1000ms. If a key is pressed during stimulus presentation then the next trial should be initiated immediately.

    I've tried adding a blank screen event that is only displayed if no response is received during the presentation interval and this works but the data file gets messy with either one or two lines per trial being recorded depending on when people respond.

    Thanks.

  • #2
    Your idea of adding a blank screen event is correct. However, rather than presenting it if there is no response, the better approach is to always present it (i.e. link it to the trial), and then skip that blank event if there *is* a response. This way, the data will not look messy in the data file.

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    • #3
      Thanks. That helps a little but if the participant responds during the blank screen the data for that trial is still recorded in two separate rows. I can't simplify this by deleting the rows with NR as the error code as that row also contains details of the randomly allocated colour the word was presented in.

      As it stands, before the results can be analysed the colour attribute from one line has to be merged with the response data in the second line for every case where the participant responded during the blank screen.

      This is not going to be very convenient. Is there any way of improving this further?

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      • #4
        post-processing (data transformation) is one option

        Hi John,

        The dilemma you are describing sounds very similar to something discussed in this thread:

        http://community.cedrus.com/showthread.php?t=1907

        If so, then you have two options (as described on thread t=1907). The options are to: (1) create a list (usually a text list) for the "blank screen" event, or (2) copy-and-paste a simple spreadsheet formula down one new column that you create (after opening the saved data in Google spreadsheets or Excel or something similar).

        If you have questions (or doubts) about applying those options to your experiment, then please attach your experiment here and we'll continue to help.

        It's interesting that you mention a colour attribute, because that is exactly what is going on in our video demo on that prior thread. (this: http://www.screencast.com/t/mROe6OU3Vj ) In the video, cell G4 is compared to K4 (both on row 4). However, you could just as easily compare K5 to G4 (comparing across rows, from 5 to 4), and the formula would still be as quick to create and paste.

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