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Probabilistic Feedback

wessa — Fri, 13 Nov 2015 05:49:28 GMT

Hi,
in a learned helplessness task I would like to insert a probabilistic feedback after a response is given by the subject, i.e. a feedback that is not contingent to the accuracy of the response. More precisely, the subject should receive a "punishment" feedback (in our case waiting for 12 sec until the next trial starts) in 75% of the trials and a "reward" feedback (waiting for only 2 sec until the next trial starts) on 25% on the trials but always irrespective of the correct or incorrect answer the subject has given.

Any idea on how I could implement that in the script? Is there any option by using the select attribute? Or by using a counter? If yes, how would I concretely write it in the script?

Thanks a lot for your help and looking forward to hopefully quick answers,
Michèle

RE: Probabilistic Feedback

wessa — Fri, 13 Nov 2015 05:49:28 GMT

Thanks a lot Dave, that helped a lot.

Best,
Michèle

RE: Probabilistic Feedback

Dave — Fri, 13 Nov 2015 04:53:18 GMT

You can, for example, enter your "punish" and "reward" trials into a <list> in the desired proportions and then /branch from your "main" trial(s):

<block myblock>
/ trials = [1-100=mytrial]
</block>

<trial mytrial>
/ stimulusframes = [1=mytext]
/ validresponse = ("d", "k")
/ correctresponse = ("k")
/ branch = [list.feedbacklist.nextvalue]
</trial>

<trial punishment>
/ stimulusframes = [1=punishtext]
/ validresponse = (0)
/ trialduration = 12000
</trial>

<trial reward>
/ stimulusframes = [1=rewardtext]
/ validresponse = (0)
/ trialduration = 2000
</trial>

<list feedbacklist>
/ items = (trial.punishment, trial.reward)
/ poolsize = 100
/ itemprobabilities = (.75, .25)
</list>

<text mytext>
/ items = ("Press D or K")
</text>

<text punishtext>
/ items = (":( Wait for 12 seconds.")
</text>

<text rewardtext>
/ items = (":) Wait for 2 seconds.")
</text>