During saccades, the eye constantly darts around a scene pausing for a short period on different parts. The dwell time on each of these points can be measured. During evaluation, dwell time may be used as a measure of the interest of the location allowing a heat map to be drawn. Long dwell time can also be used to trigger actions when eye gaze is used as an interaction technique.
Heat map of eye tracking data. Source: Tschneidr, CC BY-SA 4.0, via Wikimedia Commons
