Millisecond Forums

Ah, I apologize for the confusion on my part. I indeed mistook "redraw" to mean "render again to the screen". The alternative interpretation "sample another item" didn't even occur to me. Thanks for clarifying!

Dave, thanks a lot for responding. It's somewhat unfortunate but I guess I'll have to define 80 stimuli then.

My use of the term "redraw" was misleading. I realized that only after I posted. By "redrawing" I meant to "re-draw" an item from the counter, just like drawing in a lottery. Sorry for the confusion!

Best wishes,
  Malte

The /selectionrate on a counter or list determines the rate at which *sampling items* from it should occur, it has nothing to do with re-drawing stimuli within a trial. Consider

<block myblock>
/ trials = [1-3=mytrial]
</block>

<trial mytrial>
/ stimulusframes = [1=t1, t2, t3]
/ validresponse = (57)
</trial>

<list mylist>
/ poolsize = 3
/ selectionrate = always
</list>

<text t1>
/ items = myitems
/ position = (25%, 50%)
/ select = list.mylist.nextindex
</text>

<text t2>
/ items = myitems
/ position = (50%, 50%)
/ select = list.mylist.nextindex
</text>

<text t3>
/ items = myitems
/ position = (75%, 50%)
/ select = list.mylist.nextindex
</text>

<item myitems>
/ 1 = "A"
/ 2 = "B"
/ 3 = "C"
</item>

vs.


<block myblock>
/ trials = [1-3=mytrial]
</block>

<trial mytrial>
/ stimulusframes = [1=t1, t2, t3]
/ validresponse = (57)
</trial>

<list mylist>
/ poolsize = 3
/ selectionrate = trial
</list>

<text t1>
/ items = myitems
/ position = (25%, 50%)
/ select = list.mylist.nextindex
</text>

<text t2>
/ items = myitems
/ position = (50%, 50%)
/ select = list.mylist.nextindex
</text>

<text t3>
/ items = myitems
/ position = (75%, 50%)
/ select = list.mylist.nextindex
</text>

<item myitems>
/ 1 = "A"
/ 2 = "B"
/ 3 = "C"
</item>

Indeed, as you suggested, a stimulus element is evaluated *once* at the beginning of the trial (when it's prepared) -- redrawing repeatedly in the course of the trial it will not change what it displays. You are also correct in assuming this behavior is due to performance reasons. It cannot be changed, separate elements are needed.

In the meantime, I tried to manually sample a new item from the counter in the "/ onprepare" property of the text stimulus.



This does not work either. It appears that the stimulus is evaluated only once in each trial, regardless of how often the stimulus is shown during the trial. Probably this is due to efficiency reasons but can that behavior be changed?

Best wishes, Malte