Varying dot numbers using random dot kinematogram

Builder
7

I am not very familiar with using this stimulus, perhaps @jon can advise. But if the Builder dot stimulus component doesn’t allow you to vary the number of dots across trials, you could presumably as an alternative create your stimulus via code (in a code component on the relevant routine). e.g. if you examine the Python script generated by Builder, you’ll see a section like this:

dots = visual.DotStim(
    win=win, name='dots',
    nDots=100, dotSize=2,
    speed=0.1, dir=0.0, coherence=1.0,
    fieldPos=(0.0, 0.0), fieldSize=1.0,fieldShape='circle',
    signalDots='same', noiseDots='direction',dotLife=3,
    color=[1.0,1.0,1.0], colorSpace='rgb', opacity=1,
    depth=-9.0)

You could add code like that to the “begin routine” tab of a code component, replacing the 100 value for nDots with your variable name, and altering other parameters as necessary.

See the API here for more information: http://www.psychopy.org/api/visual/dotstim.html