The eyetracking system in the JEL comprises two EyeLinkII head-mounted video-based eyetrackers. The official EyeLinkII site by SR Research is here.

Useful information regarding the use of the system (and problems, etc.) can be obtained from the SR Support Forum.

-- FrankKeller - 08 Nov 2005

Some tips for accurate tracking

In a scene description experiment I am currently running, I had a lot of problems with fixations always being recorded above the objects I would have expected participants to be looking at. The solution was scarily simple: for quite a while now, the screen has been tilted forward, rather than vertical. This means that the two lower head-markers are further away from the participant, which will be obvious in a non-rectangular head marker indication. Calibration values can still be fine!

So, before starting an experiment:

  • check that the screen is vertical,
  • check that the participant is sitting straight in front of it, roughly two arms' lengths' away,
  • check that the eyetracker is staight above their nose,
  • check that their gaze is roughly to the middle of the screen; otherwise adjust the height of the chair.
All of these points should lead to the IR head markers being in a close-to-perfect rectangle.

In addition, it's a good idea to

  • have instruction, calibration, and drift correction screens in the same luminance as the stimulus display,
  • remember to take the slack off the cord at the back of the head by pulling it through over the loop on the wooden stand.

Good luck!

-- HeleneK - 15 Oct 2007

Topic revision: r3 - 15 Oct 2007 - 12:01:25 - HeleneK
 
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