Millisecond Forums

> What function or syntax do I use to write that the first four stimuli are the same (but varied in size presentation) followed by a novel stimulus?

You define four stimulus elements (<text> or <picture>) with the requisite different sizes and have them all select the same item. You define one stimulus element for the novel stimulus. Then display them via a <trial>'s /stimulustimes at the desired intervals.

<values>
/ sameitem = 1
/ novelitem = 1
</values>

<block myblock>
/ trials = [1-4 = mytrial]
</block>

<trial mytrial>
/ ontrialbegin = [values.sameitem = list.itemnumbers.nextindex;
    values.novelitem = list.itemnumbers.nextindex;]
/ stimulustimes = [0=same1; 500=same2; 1000=same3; 1500=same4; 2000 = novel]
/ validresponse = (57)
</trial>

<text same1>
/ items = myitems
/ select = values.sameitem
/ fontstyle = ("Arial", 1%)
</text>

<text same2>
/ items = myitems
/ select = values.sameitem
/ fontstyle = ("Arial", 2%)
</text>

<text same3>
/ items = myitems
/ select = values.sameitem
/ fontstyle = ("Arial", 3%)
</text>

<text same4>
/ items = myitems
/ select = values.sameitem
/ fontstyle = ("Arial", 4%)
</text>

<text novel>
/ items = myitems
/ select = values.novelitem
/ fontstyle = ("Arial", 4%)
</text>

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

<list itemnumbers>
/ poolsize = 8
/ selectionrate = always
</list>

Thank you for your help.  I would like the first four items (all four of which randomly vary in size) to be the same and then the fifth face is new, though it's the same face repeated throughout the experiment and it does not run through the list of 75 faces.  Should I specify .nextvalue instead of .nextindex to rotate through the list or is there a command function to specify the first four faces are the same and the last face is different?

<trial facesequence>
/ ontrialbegin = [values.sameitem = list.itemnumbers.nextindex;
  values.novelitem = list.itemnumbers.nextindex;]
/ stimulusframes = [1 = bifaceitems1; 2 = bifaceitems2; 3 = bifaceitems3; 4 = bifaceitems4; 5 = bifaceitems_novel]
/ validresponse = (57)
/ trialduration = 1000
</trial>

You need to share the code of the <list> and <picture> elements for me to be able to answer that. The <trial> code is not relevant to your question. FWIW, if you have 75 items, the <list> ought to account for that, of course,

<list itemnumbers>
/ poolsize = 75
/ selectionrate = always
</list>

as does the number of trials you run per your <block>'s /trials attribute.

Great, here are the picture and lists properties.
<picture bifaceitems1>
/items = bifaceitems
/size = (50%, 50%)
/select = values.itemnumber
/ erase = false
</picture>

<picture bifaceitems2>
/items = bifaceitems
/size = (70%, 70%)
/select = values.itemnumber
/ erase = false
</picture>

<picture bifaceitems3>
/items = bifaceitems
/size = (90%, 90%)
/select = values.itemnumber
/ erase = false
</picture>

<picture bifaceitems4>
/items = bifaceitems
/size = (30%, 30%)
/select = values.itemnumber
/ erase = false
</picture>

<picture bifaceitems_novel>
/items = bifaceitems
/size = (90%, 90%)
/select = values.itemnumber
/ erase = false
</picture>

<list itemnumbers>
/ poolsize = 75
/ selectionrate = always
</list>

<picture bifaceitems_novel>
/items = bifaceitems
/size = (90%, 90%)
/select = values.itemnumber
/ erase = false
</picture>

this seems wrong. Given your <trial> code

<trial facesequence>
/ ontrialbegin = [values.sameitem = list.itemnumbers.nextindex;
  values.novelitem = list.itemnumbers.nextindex;]
/ stimulusframes = [1 = bifaceitems1; 2 = bifaceitems2; 3 = bifaceitems3; 4 = bifaceitems4; 5 = bifaceitems_novel]
/ validresponse = (57)
/ trialduration = 1000
</trial>

If <picture bifaceitems_novel> is supposed to display a different item than <picture bifaceitems1> to <picture bifaceitems4>, this ought to read

<picture bifaceitems_novel>
/items = bifaceitems
/size = (90%, 90%)
/select = values.novelitem
/ erase = false
</picture>

and /select = values.sameitem in

<picture bifaceitems1>
/items = bifaceitems
/size = (50%, 50%)
/select = values.sameitem
/ erase = false
</picture>

to

<picture bifaceitems4>
/items = bifaceitems
/size = (30%, 30%)
/select = values.sameitem
/ erase = false
</picture>

I don't know where you get values.itemnumber from -- it isn't used anywhere in your <trial>.

Thank you for your help.  I am having a hard time with randomizing the size of each image within each trial. The sizes are separately defined for each picture, ranging from 30% to 90%, and I would like these sizes to be randomly selected while maintaining the order of face presentation (the first four faces are old, the last face is new).  I tried to randomize the size elsewhere but an error message keeps propagating. Where do I define the randomization of face size?

<counter list>
/ select = sequence(bifaceitems1, bifaceitems2, bifaceitems3, bifaceitems4, bifaceitems_novel)
/ resetinterval = 0
</counter>

<picture bifaceitems1>
/items = bifaceitems
/size = (50%, 50%)
/ erase = false
</picture>

<picture bifaceitems2>
/items = bifaceitems
/size = (70%, 70%)
/select = values.sameitem
/ erase = false
</picture>

<picture bifaceitems3>
/items = bifaceitems
/size = (90%, 90%)
/select = values.sameitem
/ erase = false
</picture>

<picture bifaceitems4>
/items = bifaceitems
/size = (30%, 30%)
/select = values.sameitem
/ erase = false
</picture>

<picture bifaceitems_novel>
/items = bifaceitems
/size = (90%, 90%)
/select = values.novelitem
/ erase = false
</picture>

<list itemnumbers>
/ poolsize = 75
/ selectionrate = always
</list>

<values>
/itemnumber = 0
/category = 0
/block = 0
/responsekey = 57

/fixationduration = 500

/sameitem = 1
/novelitem = 1
</values>

<trial facesequence>
/ ontrialbegin = [values.sameitem = list.itemnumbers.nextindex;
  values.novelitem = list.itemnumbers.nextindex;]
/ stimulustimes = [0 = bifaceitems1; 167 = bifaceitems2; 333 = bifaceitems3; 500 = bifaceitems4; 667 = bifaceitems_novel]
/ validresponse = (57)
/ trialduration = 833
</trial>

You should put the different sizes in a <list> and then randomly assign a size to each picture element /ontrialbegin.

<list sizes>
/ items = (30%, 50%, 70%, 90%)
/ selectionrate = always
</list>

<trial facesequence>
/ ontrialbegin = [values.sameitem = list.itemnumbers.nextindex;
  values.novelitem = list.itemnumbers.nextindex;]
/ ontrialbegin = [picture.bifaceitems1.height = list.sizes.nextvalue;
    picture.bifaceitems1.width = list.sizes.currentvalue;

    picture.bifaceitems2.height = list.sizes.nextvalue;
    picture.bifaceitems2.width = list.sizes.currentvalue;

    picture.bifaceitems3.height = list.sizes.nextvalue;
    picture.bifaceitems3.width = list.sizes.currentvalue;

    picture.bifaceitems4.height = list.sizes.nextvalue;
    picture.bifaceitems4.width = list.sizes.currentvalue;
]
...
</trial>