Hi,
I have an experiment where participants have to choose which of three images they have seen before. Each image has a number underneath (1,2 and 3 - always in the same locations) they enter the number on the keyboard that corresponds to the number underneath the correct image - but the location of the images is random.
I've done this by setting the image positions with a counter - see below
<picture D>
/ items = ("D.png")
/ hposition = counter.poscounter.selectedvalue
/ vposition = 50
</picture>
<picture D2>
/ items = ("D2.png")
/ hposition = counter.poscounter.selectedvalue
/ vposition = 50
</picture>
<picture Dcorrect>
/ items = ("Dcorrect.png")
/ hposition = counter.poscounter.selectedvalue
/ vposition = 50
</picture>
<counter poscounter>
/ items = (25, 50, 75)
/ select = noreplace
/ selectionrate = always
</counter>
So this means the correct response will vary on every trial depending on which location picture.Dcorrect is allocated to. I have tried to record the correct response based on location in an expression update in the trial. But I can't get this to work, the data records expressions.correctpos as 1 every time and always thinks the correct response is pressed even when it's not. The trial is below...
<trial doughnut>
/ ontrialbegin = [
values.category= "food"
]
/ ontrialbegin = [if (picture.Dcorrect.hposition= 25) expressions.correctpos = "1"
else if(picture.Dcorrect.hposition= 50) expressions.correctpos = "2"
else if(picture.Dcorrect.hposition= 75) expressions.correctpos = "3"]
/ stimulusframes = [1=D, D2, Dcorrect, no1, no2, no3]
/ validresponse = ("1", "2", "3")
/ iscorrectresponse = [expressions.correctpos]
/ ontrialend = [
if (trial.doughnut.correct) {
values.foodcorrect +=1
}
]
</trial>
- In addition two of the images seem to overlap sometimes - but not consistently?
Any help would be appreciated. I have attached a shortened version of the script too.
Thank you