Millisecond Forums

<block myblock>
/ trials = [1-5 = mytrial]
</block>

<trial mytrial>
/ ontrialend = [list.imagelist.reset(); ]
/ stimulusframes = [1=img1, img2, img3, img4]
...
</trial>

<picture img1>
/ items = imageitems
/ select = list.imagelist.nextindex
...
</picture>
...
<picture img4>
/ items = imageitems
/ select = list.imagelist.nextindex
...
</picture>

<list imagelist>
/ poolsize = 10
/ selectionrate = always
</list>

<item imageitems>
/ 1 = "circle1.jpg"
...
/ 10 = "circle10.jpg"
</item>

It looks fine, but there is one problem.The onscreen position of each image is not set within the jpg file.It is set in the picture element for each object, this is:

< picture circle_1>
/ items = ("circle_1.jpg")
/ vposition = 5
/ hposition = 5
</picture>

<picture circle_1>
/ items = ("circle_2.jpg")
/ vposition = 10
/ hposition = 10<
/picture>
...
<picture circle_10>
/ items = ("circle_10.jpg")
/ vposition = 95
/ hposition = 95
</picture> 

How should I implement these picture elements in item element in order to use it in the list element?
Is it possible?
If no, is there any other way I can get 4 random pictures out of 10 pictures (such as presented just above) in each trial?

You can define two additional list elements (one for hposition, one for vposition) and link them to the 1st list. EDITED Here's a full example with <text> elements (it works the same for <picture>s):

<block myblock>
/ trials = [1-10 = mytrial]
</block>

<trial mytrial>
/ ontrialend = [list.mylist.reset(); ]
/ stimulusframes = [1=txt1, txt2, txt3, txt4]
/ validresponse = (57)
</trial>

<text txt1>
/ items = myitems
/ select = list.mylist.nextindex
/ hposition = list.hpos.nextvalue
/ vposition = list.vpos.nextvalue
</text>

<text txt2>
/ items = myitems
/ select = list.mylist.nextindex
/ hposition = list.hpos.nextvalue
/ vposition = list.vpos.nextvalue
</text>

<text txt3>
/ items = myitems
/ select = list.mylist.nextindex
/ hposition = list.hpos.nextvalue
/ vposition = list.vpos.nextvalue
</text>

<text txt4>
/ items = myitems
/ select = list.mylist.nextindex
/ hposition = list.hpos.nextvalue
/ vposition = list.vpos.nextvalue
</text>

<item myitems>
/ 1 = "A"
/ 2 = "B"
/ 3 = "C"
/ 4 = "D"
/ 5 = "E"
/ 6 = "F"
/ 7 = "G"
/ 8 = "H"
/ 9 = "I"
/ 10 = "J"
</item>

<list mylist>
/ poolsize = 10
/ selectionrate = always
</list>

<list hpos>
/ items = (5%,10%,15%,20%,25%,75%,80%,85%,90%,95%)
/ selectionmode = list.mylist.currentindex
/ selectionrate = always
</list>

<list vpos>
/ items = (5%,10%,15%,20%,25%,75%,80%,85%,90%,95%)
/ selectionmode = list.mylist.currentindex
/ selectionrate = always
</list>

Works perfectly!
Thank you very much Dave.