random stimulus fixed by participant

charlottebooth — Fri, 03 Nov 2017 10:39:24 GMT

Hey,

I'm having trouble randomizing my stimulus set.

Imagine you have three levels of reward (e.g. +£1, +£2, +£3) which are given according to different stimuli (e.g. square, circle, triangle) but you want to randomize this by participant so that e.g. participant 1 always has £1 for a square, but this is different for each participant. How would you go about this? Is there a type of selection that would work, or is there much more code involved that creates specific lists for each participant at the beginning of the experiment?

<picture shapes>
/erase = false
/items = ("square.png", "circle.png", "triangle.png")
/position = (50, 50)
/select = ???
</picture>

<trial reward1>
/stimulustimes = [0 = pointstotal, shape]
/trialduration = 3000
/correctresponse = (lbuttondown)
/validresponse = (noresponse)
/validresponse = (lbuttondown)
/ontrialend = [if (trial.reward.correct) values.pointstotal +=1;]
</trial>

RE: random stimulus fixed by participant

Dave — Fri, 03 Nov 2017 10:39:24 GMT

[quote]

[b]charlottebooth - Friday, November 3, 2017[/b]

[/quote]

Link a <list> containing three values to the <picture> element.

<picture shapes>
/erase = false
/items = ("square.png", "circle.png", "triangle.png")
/position = (50, 50)
/select = noreplace
</picture>

<list rewards>
/ items = (values.squarereward, values.circlereward, values.trianglereward)
/ selectionmode = picture.shapes.currentindex
</list>

with

<values>
/ squarereward = 0
/ circlereward = 0
/ trianglereward = 0
</values>

Set the three values randomly to either 1, 2 or 3 /onexptbegin

<list rewardamounts>
/ items = (1,2,3)
/ selectionrate = always
</list>

<expt>
/ onexptbegin = [values.squarereward = list.rewardamounts.nextvalue; values.circlereward = list.rewardamounts.nextvalue; values.trianglereward = list.rewardamounts.nextvalue; ]
...
</expt>

Then, in your <trial> you simply do:

<trial reward1>
/stimulustimes = [0 = pointstotal, shape]
/trialduration = 3000
/correctresponse = (lbuttondown)
/validresponse = (noresponse)
/validresponse = (lbuttondown)
/ontrialend = [if (trial.reward.correct) values.pointstotal +=list.rewards.nextvalue;]
</trial>

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random stimulus fixed by participant

RE: random stimulus fixed by participant