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Presenting a random number of dots

Lizzy — Sat, 25 Nov 2023 10:16:35 GMT

G'day,
I'm trying to set up a task where participants will see a cluster of dots on the left hand side of screen, and another cluster of dots on the right. The task is to indicate which cluster has more dots in it.
I want each trial to present a random number of dots (between 50 and 100) on one side. The other cluster will have x number of dots more or less than the first cluster (x will vary across trials to manipulate difficulty).
My problem is that I can't figure out how to present a random number of dots. I've tried a few things but always get stuck somewhere. My latest idea was to always present the maximum number of dots (i.e. 100), and then try to make a small subset of them the same colour as the background, essentially making them go away. I've attached the script I tinkered with, which presents 20 dots on the left. The bit of code I tried to use in the trial element to make some of the dots white isn't working because clearly I can't use the <%%> code in this way. I can't figure out another way though.

<trial dottrial>
/ ontrialbegin = [list.dotlist.reset();
var i = 0;
while (i < values.selectnumber) {
shape.<%list.dotlist.nextvalue%>.color = white;
i += 1;
};
]
/ stimulusframes = [1 = dot1, dot2, dot3, dot4, dot5, dot6, dot7, dot8, dot9, dot10, dot11, dot12, dot13, dot14, dot15, dot16, dot17, dot18, dot19, dot20]
/ validresponse = (57)
</trial>

Could I get there with this approach? Or is this never going to work?

RE: Presenting a random number of dots

Lizzy — Sat, 25 Nov 2023 10:16:35 GMT

Thank you Dave, that solved the issue. I hadn't thought of the 'insertstimulusframe' function. Thanks so much for your help!!

RE: Presenting a random number of dots

Dave — Fri, 24 Nov 2023 12:53:55 GMT

+x[quote]

[b]Lizzy - 11/24/2023[/b]
G'day,
I'm trying to set up a task where participants will see a cluster of dots on the left hand side of screen, and another cluster of dots on the right. The task is to indicate which cluster has more dots in it.
I want each trial to present a random number of dots (between 50 and 100) on one side. The other cluster will have x number of dots more or less than the first cluster (x will vary across trials to manipulate difficulty).
My problem is that I can't figure out how to present a random number of dots. I've tried a few things but always get stuck somewhere. My latest idea was to always present the maximum number of dots (i.e. 100), and then try to make a small subset of them the same colour as the background, essentially making them go away. I've attached the script I tinkered with, which presents 20 dots on the left. The bit of code I tried to use in the trial element to make some of the dots white isn't working because clearly I can't use the <%%> code in this way. I can't figure out another way though.

<trial dottrial>
/ ontrialbegin = [list.dotlist.reset();
var i = 0;
while (i < values.selectnumber) {
shape.<%list.dotlist.nextvalue%>.color = white;
i += 1;
};
]
/ stimulusframes = [1 = dot1, dot2, dot3, dot4, dot5, dot6, dot7, dot8, dot9, dot10, dot11, dot12, dot13, dot14, dot15, dot16, dot17, dot18, dot19, dot20]
/ validresponse = (57)
</trial>

Could I get there with this approach? Or is this never going to work?
[/quote]

You should put all dot shapes in a list, figure out how many you want to present /ontrialbegin (e.g. draw a random value between min dots and max dots), then add the requisite number of dots to the trial's stimulus presentation sequence by using the insertstimulusframe() function in a loop.

[code]<trial dottrial>
/ ontrialbegin = [
    trial.dottrial.resetstimulusframes();
    list.dotlist.reset();
    values.selectnumber = round(rand(5, 20));
    var i = 0;
    while (i < values.selectnumber) {
    trial.dottrial.insertstimulusframe(list.dotlist.nextvalue, 1);
    i += 1;
    };
]
/ stimulusframes = [1=clearscreen]
/ validresponse = (57)
</trial>

<list dotlist>
/ items = (shape.dot1, shape.dot2, shape.dot3, shape.dot4, shape.dot5, shape.dot6, shape.dot7, shape.dot8, shape.dot9, shape.dot10,
    shape.dot11, shape.dot12, shape.dot13, shape.dot14, shape.dot15, shape.dot16, shape.dot17, shape.dot18, shape.dot19, shape.dot20)
/ selectionmode = sequence
/ selectionrate = always
</list>[/code]