Running Experiments on LookIt
How to Run an Experiment on LookIt
Last updated
How to Run an Experiment on LookIt
Last updated
Are you covered by the IRB?
Are all of your surveys online? (either in LookIt, or in Qualtrics)
Do you have written / video instructions? (remember: no experimenter!)
Do you have a pipeline to code the data? Is there sufficient metadata with every trial?
Do you have a way to compensate participants?
Do you know how you are going to recruit participants? If using RPAD remotely, do you have VPN access and appropriate permission?
Generating Video Assets In Experiment Builder
All of our existing eyetracking experiments are composited in Experiment Builder (EB): we specify image and audio assets, as well as a timeline and a randomization scheme, but then EB actually draws the frames of the video. To avoid having to write our own compositing code (ie drawing frames programmatically as images in R or Python and then concatenating them into a video with ffmpeg), we can instead use Experiment Builder in “Dummy mode” to preview the experiment; we can then capture this output with a screen and audio recorder (OBS), then slice it into individual trials that can be used on LookIt. Note that this approach may be less fun if you have many conditions with trials of varying lengths, in that this will take a lot of time to slice and save the individual trials (vs. programmatic composition, where this wouldn’t be a problem)
There are three major hurdles with the above approach: 1) getting a licensed version of Experiment Builder 2) getting the right video settings so that Experiment Builder will play the preview 2) capturing the audio from the dummy experiment in Experiment Builder.
#1) Get a licenced version of Experiment Builder. Generally this is hard and requires a hardware token, but SR Research is giving away 150-day temporary licences so that researcher can keep running during COVID. Fill out the form on their website and they will send you one.
#2) Get the right video settings so that Experiment Builder will preview the experiment in “Dummy mode.” To activate Dummy Mode, click the eyetracker in the Devices panel and find the Dummy mode button. Running the experiment will fail, however, unless your screen is in the precise Display configuration format in the Experiment Builder properties. Rather than change these properties (which may require changing x and y positions of stimuli on the screen), the easier thing to do is to make your machine match these properties. On a Mac, this is mostly easily achieved by installing SwitchResX and adding a custom resolution (1280*1024)
Choose the display profile on the left panel, and go to the “Custom resolutions” tab, and add a new scaled resolution
You should then be able to select that and then hit “Activate immediately.” Your screen will decrease in resolution and areas to the left and right will turn black. Not great, but now Experiment Builder can run.
#3. Capturing audio from Experiment Builder. For some reason, OBS can’t capture system sound unless you install a plugin called IShowU Audio Capture Once installed, this will show up as an option in the audio output menu (like Headphones or Internal speakers). Note that if you select it, you will no longer hear audio from your Mac (it is getting routed to the audio capture as a device, not to speakers or headphones). To fix this, follow the instructions to make a “multi output device” here
With these three things in place, you should be ready to record the experiment in OBS. Under the sources for the scene, you will want a Display Capture for Display 0, and an Audio Input Capture with IShowU as the source. Turn the gain on the internal mic (associated with the Display capture) to 0 so that you don’t record through the microphone.
