[solved] Flashing stimuli & overlayed sketchpads?

jpg · February 2012

Hi Sebastian,

I've been enjoying OpensSesame so far, it's great to work with!

I was wondering if it is possible to have visual stimuli (something simple, a fixation dot will do) flash on and off a number of times (the number of times it flashes will be determined by a loop variable)

To complicate things, I need it to be flashing while other sketchpad items remain constant on the screen... I was thinking it might involve multiple canvases overlayed on each other?

Any advice?

Jamie

sebastiaan · February 2012

Hi Jamie,

Yes, sure. There are many ways to do this, but the easiest way (which will require minimal inline coding) is probably as follows:

Create a "template" sketchpad that contains the constant image and add it somewhere to the start of the experiment. You can give it a 0ms duration to make sure you don't notice it—it's only there to serve as a template.
Add a variable to the block_loop that contains the number of repetitions. Let's call it "repetitions".
Add the following to the run phase of an inline_script in the trial sequence. This will show a flashing display:

my_canvas1 = self.copy_sketchpad("template")
my_canvas2 = self.copy_sketchpad("template")
my_canvas2.fixdot()
for i in range(self.get("repetitions")):
    my_canvas1.show()
    self.sleep(100)
    my_canvas2.show()
    self.sleep(100)

I guess the code is fairly self explanatory. For more canvas functions, please refer to the documentation:

http://osdoc.cogsci.nl/python-inline-code/canvas-functions

Hope this gets you started!

Regards,
Sebastiaan

jpg · February 2012

Thanks Sebastian, that worked!

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[solved] Flashing stimuli & overlayed sketchpads?

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[solved] Flashing stimuli & overlayed sketchpads?

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