Gaze contingent fixation cross
Hi,
I would like to implement a gaze-contingent fixation cross for my experiment. I am using Eyelink2 and OpenSesame (fresh install) on Ubuntu.
INTENDED BEHAVIOUR: the fixation cross is shown and the computer waits for a keypress. The trial proceeds only when a key is pressed AND the participant's gaze is within some distance from the fixation cross.
ALTERNATIVELY: The trial proceeds anyway when a key is pressed, but in the log I can see whether the fixation distance was in a tolerable limit.
I don't need to record gaze after fixation, but I guess I would need to (and stop recording later) -- Eyelink usually needs some pause after starting/stopping recording, but I need to show some time critical sequence after the fixation cross. Does anyone have experiences with such implementation?
I have some experiences with Python, PsychoPy and Pylink, but I am pretty new to OpenSesame.
What is a correct way to implement this behaviour in OpenSesame and preferably maintain the compatibility with other OpenSesame elements (calibration etc.)?
I have seen there was a plugin for a similar task in previous version, but it is out-dated, right?
Thanks in advance for your help!
Comments
Hi,
What you describe here, is basically covered by the drift correction item alone. In the drift correction, participants focus on a centrally positioned dot and have to press the spacebar. The system then aligns the eye position coordinates at the time of the key press with the screen center. This also implies a potential problem for your setup; there is always going to be drift.
Cheers
Josh
Thanks @Josh, I will test it in my experiment.
I knew about drift correction and it is a handy solution because you can use it for an additional setup. However, I have bad experiences with drift correction as a fixation cross, because it is sometimes repeated and it attracts unnecessary attention and confuses participants.