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Thread: How do I determine a correct button press on the fly?

  1. #1
    Join Date
    Mar 2008
    Posts
    3

    How do I determine a correct button press on the fly?

    I have looked through the manual, tutorials, and forum but haven't quite found what I am looking for yet. I am designing a masked-priming, lexical decision experiment. I looked at the lexical decision example in the tutorial but that experiment seems to have word and nonword targets alternating every 4th trial or so. I would like to make sure that the order of word and nonword targets is random across trials. Ideally I'd like the experiment procedure to work as follows, but I am amenable to other suggestions to get it to work in DirectRT 2006.

    For each trial, I would like to randomly select a prime from a text file (called prime.txt). Each prime would then be paired with a predesignated word or nonword target taken from a different, single text file (called target.txt). It is critical that the prime and target are paired together based on the order in which they occur in their respective text files. I was able to get the random prime-target selection process to work in DirectRT. The trouble I am having is that in randomly selecting a prime and its designated target, I am not sure which key repsonse will be the correct one for each trial before hand because the target can either be a word or a nonword and would require a different key repsonse accordingly. Is there a way to set up the 'time' column in the directRT input file to determine the correct response on the fly (e.g. all word targets require the Z key and all nonwords targets require the / key)?
    I could create another text file with the correct key responses because it would reflect the same prime-target order determined by the prime.txt and target.txt files. However, I'm not sure if I could access that file from the time column. If that is not possible, are there other ways of addressing the issue?

    Thank you,
    Brandon

  2. #2
    Join Date
    Nov 2005
    Posts
    3,323
    I see you've already been through this thread on how to yoke pairs of stimuli:

    http://www.empirisoft.com/support/showthread.php?t=549

    Unfortunately, DirectRT does not have a function to determine "correct" on the fly. It would have to be calculated via post-test analysis.

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