Counter element and sequential selection

Zooahh — Mon, 27 Oct 2014 06:38:47 GMT

Hi,

I am trying to set up a AX-CPT task where, during the practice block, participants are supposed this serie of letters :
W X A P T A X A Z A X B X A X
(in this order)

With the following script I get a serie of 15 letters but randomly chosen from the list of items axletters and I can't figure out why...

<values>
/ resttime = 120000
/ cresp = 0
/ stimtype = 0
</values>

<item axletters>
/ 1 = "A"
/ 2 = "B"
/ 3 = "C"
/ 4 = "D"
/ 5 = "E"
/ 6 = "F"
/ 7 = "G"
/ 8 = "H"
/ 9 = "I"
/ 10 = "J"
/ 11 = "K"
/ 12 = "L"
/ 13 = "M"
/ 14 = "N"
/ 15 = "O"
/ 16 = "P"
/ 17 = "Q"
/ 18 = "R"
/ 19 = "S"
/ 20 = "T"
/ 21 = "U"
/ 22 = "V"
/ 23 = "W"
/ 24 = "X"
/ 25 = "Y"
/ 26 = "Z"
</item>

<text stimi>
/items = axletters
</text>

<text errormessage>
/ items = (" ERROR ")
/ txcolor = (255,0,0)
</text>

<text correctmessage>
/ items = (" CORRECT ")
/ txcolor = (0,255,0)
</text>

<shape blank>
/ shape = rectangle
/ color = white
/ size = (50%, 50%)
</shape>

<counter practicelettersstimtype>
/ items = (23,24,1,16,20,1,24,1,26,1,24,2,24,1,24)
/ select = sequence
</counter>

<counter practiceletterscresp>
/ items = (50,50,50,50,50,50,44,50,50,50,44,50,50,50,44)
/ select = current(practicelettersstimtype)
</counter>

<trial practiceletters>
/ stimulustimes = [1 = stimi; 500 = blank]
/ ontrialbegin = [values.stimtype=counter.practicelettersstimtype.selectedvalue;
values.cresp=counter.practiceletterscresp.selectedvalue]
/ trialduration = 1000
/ validresponse = (44,50)
/ iscorrectresponse = [trial.practiceletters.response==values.cresp]
/ responsetime = 1000
</trial>

<block prac>
/ trials = [1-15= noreplace(practiceletters)]
/ errormessage = (errormessage, 400)
/ correctmessage = (correctmessage, 400)
</block>

Thank you for your help!

RE: Counter element and sequential selection

Zooahh — Mon, 27 Oct 2014 06:38:47 GMT

Thank you!

RE: Counter element and sequential selection

Dave — Fri, 24 Oct 2014 15:02:14 GMT

<text stimi>
/items = axletters
</text>

If you don't specify its /select attribute otherwise, any stimulus element (such as a <text>) defaults to random selection without replacement. That's the expected behavior.

If you want it to use e.g. a <counter> for selection, you need to specify that explicitly.

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Counter element and sequential selection

RE: Counter element and sequential selection

RE: Counter element and sequential selection