By Cathy! - 12/9/2014
hey everybody,
we have two questions:
1. we are trying to create a trial element with the following properties:
we have a text element (instructions) which should be presented for 10 minutes. during the presentation, participants should have the opportunity to press the 't'-key in order to listen to a sound stimulus as often as they like. the text element should be visible the whole time, no matter if they press the key (once/more than once) or not. we want the frequency (number of times participants press the key) to be recorded.
2. for another experiment, we want a block with the following properties:
every time a specific sound stimulus appears, a surverypage should be presented. we want the sound+surverypage (the same every time) to appear three times within 15 minutes, the rest of the time the screen should be all black. the sound+surveypage should appear at three random points of time within the 15 minutes, but there should be at least three minutes in between (at least three minutes black screen) each sound+surveypage.
does anyone have an idea? thank you for helping!
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By Dave - 12/9/2014
Re. #1: Use /bgstim to display the <text> instructions element throughout the block. You need to make sure that no other stimulus displayed by your trials ever overwrites said <text> element (or else it will be gone). In your <trial>s, designate some response for the audio stimulus. If that response occurs in a <trial>, /branch to a dedicated <trial> that plays the audio.
Re. #2: Set up a <trial> that displays a black screen and accepts no response. Set up another <trial> that plays the audio file and upon completion does a /branch to the <surveypage>.
<block someblock>
/ trials = [1=sequence(blackscreentrial, audiotrial, blackscreentrial, audiotrial, blackscreentrial, audiotrial, blackscreentrial)]
...
</block>
Use <expressions>, <values>, etc. to calculate suitable durations for the blackscreen trials, such that the temporal distance between audio trials is >= 120000ms and the overall duration of the trial sequence approximates 15 mins.
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