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Group: Administrators
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The basic mechanics go like this (using <text> elements for the sake of example; it works the same with <picture> elements):
<block myblock>
/ trials = [1-10 = choicetrial]
</block>
<trial choicetrial>
/ inputdevice = mouse
/ stimulusframes = [1=safe, risky]
/ validresponse = (safe, risky)
/ branch = [if (trial.choicetrial.response == "safe") list.safechoice.nextvalue]
/ branch = [if (trial.choicetrial.response == "risky") list.riskychoice.nextvalue]
</trial>
<text safe>
/ items = ("SAFE")
/ position = (40%, 50%)
</text>
<text risky>
/ items = ("RISKY")
/ position = (60%, 50%)
</text>
<list safechoice>
/ items = (trial.20loss, trial.20gain, trial.10loss, trial.10gain)
/ itemprobabilities = (.10, .10, .40, .40)
/ poolsize = 10
/ replace = true
</list>
<list riskychoice>
/ items = (trial.20loss, trial.20gain, trial.10loss, trial.10gain)
/ itemprobabilities = (.40, .40, .10, .10)
/ poolsize = 10
/ replace = true
</list>
<trial 20loss>
/ stimulusframes = [1=20losstxt]
/ validresponse = (57)
</trial>
<trial 20gain>
/ stimulusframes = [1=20gaintxt]
/ validresponse = (57)
</trial>
<trial 10loss>
/ stimulusframes = [1=10losstxt]
/ validresponse = (57)
</trial>
<trial 10gain>
/ stimulusframes = [1=10gaintxt]
/ validresponse = (57)
</trial>
<text 20losstxt>
/ items = ("-20 points")
</text>
<text 20gaintxt>
/ items = ("+20 points")
</text>
<text 10losstxt>
/ items = ("-10 points")
</text>
<text 10gaintxt>
/ items = ("+10 points")
</text>
The two <list> elements are responsible for the varying probabilistic outcomes based on "safe" vs. "risyk" choice.
The 20gain, 20loss, etc. <trial> elements would be used to present the respective images instead of <text> elements; you would hanclle any scoring (if so desired) via /ontrialbegin or -end logic in those <trial> elements.
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