8 People can miss changes in their visual field

Eye tracking is a technology that can track where someone is looking. 

More specifically, it tracks where the foveal or central gaze is.

Eye-tracking data can be misleading. 

Reason 1. It tells yo what people looked at, but that doesn't mean they paid attention to it.

Reason 2. Eye-tracking only measures central vision.

Reason 3. It's easy to accidentally skew the eye-tracking dat depending on what instructions you give them before and during the eye tracking study.