[open] Limit number of fixations for Open Sesame Eye link Exp

Olya

Hello!
For my face recognition experiment, I need to limit the number of fixations my participants are allowed to have while looking at a face. Is there a way to do so in Open Sesame? I have it connected to EyeLink already.

sebastiaan

Hi Olya,

This will require a bit of inline scripting, but not much. Basically, you can make use of the wait_for_fixation_start() function like so:

n_fixations = 5
print('Wating for %d fixations' % n_fixations)
for i in range(n_fixations):
    exp.eyelink.wait_for_fixation_start()
    print('Detected start of fixation %d' % i)
print('Done!')

See also:

• http://osdoc.cogsci.nl/devices/eyelink/#libeyelink.wait_for_fixation_start

Alternatively, if you don't like scripting, you could use the eyelink_wait plug-in, set the event to 'Fixation start', and put it in a loop to repeat it a few times. The inline_script way is a bit more straightforward, though.

Cheers!
Sebastiaan

Olya

Thank you Sebastian! So do I just type in the code above into the inline script Run window? The inline script is located above the sketchpad with all my face photos. Is that it?

sebastiaan

Hi Olya,

Yes, you can copy-paste the code into the run window of an inline_script. I suspect that you will have to place it below the sketchpad with the photo's though, because you want the fixation checks to occur after the photo's have appeared, right?

I would also recommend walking through some basic Python tutorials. Some knowledge of Python will be very convenient if you want to do online checks, gaze-contingency, etc, with the Eyelink. See:

• http://osdoc.cogsci.nl/python/about/#learning-python

Cheers!
Sebastiaan

Olya

Hi Sebastian,
I have switched to pygaze plug-ins, so the code above doesn't work anymore. Could you please post the pygaze equivalent of it?
Thank you very much.

Edwin

Hi Olya,

Replace exp.eyelink with exp.pygaze_eyetracker, and everything should work the same.

Good luck!