By estarska - 1/12/2016
Sorry about this simple question but I want my trial to look like this: 1) fixation_cross presented for 500 ms, 2) study_board presented as long as a participant presses a spacebar, and 3) test_board presented for as long as a person presses either "B" or "N".
So I would need to define valid response for study_board and valid and correct response for test_board separately. Also latencies for both responses should be recorded in separate variables. What would be the most efficient way to do that?
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By Dave - 1/12/2016
You need two <trial> elements to do that:
<trial a>
/ stimulustimes = [0=fixation_cross; 500=study_board]
/ validresponse = (" ")
/ branch = [trial.b]
</trial>
<trial b>
/ stimulustimes = [0=test_board]
/ validresponse = ("B", "N")
...
</trial>
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By estarska - 1/12/2016
Dave, thank you very much for your reply! I thought it would probably solve the problem. But now I have 4 types of study boards and for each study board there are 6 possible types of test boards. I want counterbalancing to be based on test board types rather than study boards. Also, for a given test board there is a particular study board that needs to be presented before (they cannot be randomly drawn). Do you have any suggestions how blocks should be defined to take these into account?
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By Dave - 1/12/2016
> I want counterbalancing to be based on test board types rather than study boards.
I'm not sure what that means in concrete terms. Counter-balance what and how exactly? Between-subjects? Within-subjects? etc. A specific example would be helpful here.
> Also, for a given test board there is a particular study board that needs to be presented before (they cannot be randomly drawn).
You can pair your study- and testboard items as needed. See the "How to present stimulus pairs" topic in the documentation for details.
Also, I don't see why having a single <trial> element to display both study- and testboard would somehow avoid those two issues. If you have worked those out for the single -<trial>-element case, the solution should apply to the two-<trial>-case as well.
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By estarska - 1/12/2016
The problem is that stimulus pairing wouldn't work, would it? what I need is rather trial pairing - as both of the stimuli (study board and test board) require participant's response and thus two separate <trial> elements are needed. I could build a bunch of two-trial blocks and then build an experiment out of that but it does not seem to be a very neat solution as it would yield a lot of blocks...
By counterbalancing i meant within- subject design so the number of test boards of each type presented to a participant.
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By Dave - 1/13/2016
> The problem is that stimulus pairing wouldn't work, would it?
The stimulus pairing works the same -- regardless of whether you have both stimuli in a single <trial> or in two separate <trial> elements.
And for "trial"-pairing, you can use conditional branching (cf. /branch attributes) to invoke the proper "testboard" <trial> element from the respective "studyboard" <trial> element.
> I could build a bunch of two-trial blocks [...]
That seems entirely unnecessary.
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By estarska - 1/13/2016
Try to use conditional branching as you suggested. Thank you very much for your help!
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By Dave - 1/13/2016
If you get stuck, post a small concrete example [1] that illustrates your intended procedure here. Then I can give you a more specific response (including example code) on how to go about implementing it.
[1] I.e. using fewer items, types and/or categories; just enough to get a sense of your intended procedure and the stimulus interdependencies.
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