Dwell Time

Comments

• cesco

  August 2019 edited August 2019

  Yes, definitely possible! To get started, see the PyGaze aoi plugin.

  Since running a timer AND checking each gaze sample during this timer can be computationally heavy, what I tend to do is the following. I present a sketchpad with for example a gaze-contingent fixation cross for a set duration (e.g. 495 ms). At the beginning of my experiment I would have defined the aoi in an inline script; for example:

  FixAOI = AOI('circle', (my_center_hor, my_center_ver), 100) # "my centers" are defined previously. 100 is the size I picked since you need some tolerance.
  

  After the sketchpad, I have another inline script that checks if a fixation occurs in your aoi. It's also handy to build in a key-escape, in case of eyetracking drama.

  while True:
    key, timestamp = my_keyboard.get_key()
    time, gazepos = eyetracker.wait_for_fixation_start()
    if key == 'x': 
      break
      # Press X to exit the loop so you can abort the experiment for example
    elif FixAOI.contains(gazepos):
      break
      # Exits the loop and thus continues to the next screen if a fixation is detected in your aoi
  

  
  

  In my example, a fixation cross always appears for a fixed duration of 500ms followed by establishing a brief fixation (default = 5 stable samples I believe). In practice, participants will just look at the fixation cross all the time as instructed -you could always check this offline-. I find this to be a stable method. You still need good tracking and a good calibration though.

  Hope this helps!

  (Edit: standard commands are very dark grey in markdown for me; highlight the code blocks for better visibility 🙂)
• cesco

  August 2019