Millisecond Forums » Millisecond Forums » Inquisit 4 » picture selection

picture selection

SimonaH. — Mon, 09 Mar 2015 08:11:11 GMT

Hi,

I have a question on how to best programm a random selection of pictures from one pool into separate picture pools that starts at the beginning of a trial.

I have a pool of 16 pictures and at the beginning of an experiment I want them to be randomly assigned into 4 separate pools: 4 pictures per pool. These picturs will then be drawn at and presented in 4 different within design conditions (reperesnted by trials), where also other characteristics are counterbalanced (e.g. picture position).

I tried to accomplish it by creating a central list of 16 pictures and programm a very first trial of the experiment so that it randomly draws 4 pictures into one list and erases them from the central list and the same should happen for the next 3 lists. Then the lists are used as a “selection” reference in picture elements, as lists cannot be really used as “item” elements in trials etc. However, it does not seem to work well, I keep getting these errors:
“Error evaluating ´100´/: Unknown error.”
“Unable to initialze <picture xy> item number 0. Verify the item exists and its correctly defined.”

Any ideas? Thanks!

Here is my script:

<item all_central>
/1=picture1
/2=picture2
/...
/16=picture16
</item>

<picture all_central>
/ items = all_center
/select = noreplace
/ position = (50, 50)
/size = (550,600)
</picture>

<list all_central>
/ items= (all_central)
</list>

<list congruent_a>
/ items= (list.all_central)
/poolsize= 4
/selectionmode = random
</list>

<trial remove1>
/ ontrialbeginning= [list.all_central.removeitem(list.congruent_a);]
/timeout = 1
</trial>

<list incongruent_a>
/ items= (list.all_central)
/poolsize= 4
/selectionmode = random
</list>

<trial remove2>
/ ontrialend= [list.all_central.removeitem(list.incongruent_a);]
/timeout = 1
</trial>

<list congruent_b>
/ items= (list.all_central)
/poolsize= 4
/selectionmode = random
</list>

<trial remove3>
/ ontrialend= [list.all_central.removeitem(list.congruent_b);]
/timeout = 1
</trial>

<list incongruent_b>
/ items= (list.all_central)
/poolsize= 4
/selectionmode = random
</list>

<picture xyz_left_congruent_a>
/select = list.congruent_a
/ position = (25, 50)
/size = (250,300)
</picture>

<picture xyz_left_congruent_b>
/select = list.congruent_b
/ position = (25, 50)
/size = (250,300)
</picture>

<picture xyz_right_congruent_a>
/select = list.congruent_a
/ position = (75, 50)
/size = (250,300)
</picture>

<picture xyz_right_congruent_b>
/select = list.congruent_b
/ position = (75, 50)
/size = (250,300)
</picture>

<picture xyz_left_incongruent_a>
/select = list.incongruent_a
/ position = (25, 50)
/size = (250,300)
</picture>

etc..

trial example:
<trial l_congruent_left_face_a>
/inputdevice=mouse
/validresponse = ("liking_button","disliking_button")
/stimulustimes = [500=fixation_cross; 1100=face_center; 1100=xyz_left_congruent_a; 2700=facegaze_left; 3500 = x_button, y_button]
</trial>

RE: picture selection

SimonaH. — Mon, 09 Mar 2015 08:11:11 GMT

Of course, makes sense. I confused the amount of pictures in a master list, with the amount of which were supposed to be selected per list.

Now it seems to work. Thanks!

RE: picture selection

Dave — Mon, 09 Mar 2015 07:59:35 GMT

The example in my response has only 4 items, hence the <list> only has a poolsize equal to 4. For more items, you need to adjust it as needed.

<list masterlist>
/ poolsize = 16
/ selectionrate = always
</list>

You need to adjust the /onexptbegin logic accordingly as well.

RE: picture selection

SimonaH. — Mon, 09 Mar 2015 07:54:26 GMT

Hi,

thanks for the answer.

I tried to implement what you suggested (exactly), however there is still one occurring problem: I keep being presented with only the first 4 pictures from the master list over and over again (so the rest of the 16 pics does not get selected). Where could be the problem?

Simona

RE: picture selection

Dave — Fri, 06 Mar 2015 03:26:28 GMT

Your idea is along the correct lines, your syntax is erroneous in various places.

(1) Have a master <list> containing the 16 item numbers for your 16 different pictures

(2) At the beginning of the experiment populate your 4 empty <lists> representing the 4 conditions with 4 random items from that masterlist each. There is no need to remove anything from the master list.

(3) Use the condition lists for item selection in your stimulus elements.

In a nutshell:

<expt>
/ onexptbegin = [list.a.appenditem(list.masterlist.nextindex); list.a.appenditem(list.masterlist.nextindex);
list.b.appenditem(list.masterlist.nextindex); list.b.appenditem(list.masterlist.nextindex); ]
/ blocks = [1=ablock; 2=bblock]
</expt>

<block ablock>
/ trials = [1-2=atrial]
</block>

<block bblock>
/ trials = [1-2=btrial]
</block>

<trial atrial>
/ stimulusframes = [1=atxt]
/ validresponse = (57)
</trial>

<trial btrial>
/ stimulusframes = [1=btxt]
/ validresponse = (57)
</trial>

<list masterlist>
/ poolsize = 4
/ selectionrate = always
</list>

<list a>
</list>

<list b>
</list>

<text atxt>
/ items = myitems
/ select = list.a.nextvalue
</text>

<text btxt>
/ items = myitems
/ select = list.b.nextvalue
</text>

<item myitems>
/ 1 = "Item 1"
/ 2 = "Item 2"
/ 3 = "Item 3"
/ 4 = "Item 4"
</item>