Eye tracking is the measurement of eye movements. It precisely refers to recording the part of the face where the eyes are with an instrument or a camera that quantifies the movements of the eyes.
Modern eye trackers record eye position and movement based on optical tracking of corneal reflections, which allows the analysis of gaze positions or eye movements on two-dimensional screens or in three-dimensional environments.
It is implied that eye movements are translated on to what the participants are actually looking at wherefore special algorithms, that can map the eye movement onto a plain, usually a TV screen or computer monitor, are developed. This specific mapping is possible due to calibration processes where the respondents are asked to look at certain points to create a baseline. The system then understands that a certain position of the eye means that the respondent is looking at a specific point of a screen. With this information, a mathematical model can be built precisely describes where a person is looking at on the plane.
Most eye trackers utilize infrared measurements. Using the infrared spectrum rather than the visual spectrum allows for actual detection of the pupil of the eye. In this spectrum, contrast between the pupil and the iris of the eye is easily discerned. When illuminating a respondent’s face with infrared light, it will directly go through the pupil but bounce off of the iris of the eye, which makes it fairly easy to spot the center of the eye. The precise knowledge of the pupil’s center then allows the researcher to receive more accurate measurements. If researchers were to measure this in the visual spectrum, detecting the center of the pupil would be far more complicated.
In general, there is a difference between remote (or stationary/desktop) eye tracking and mobile eye tracking. For remote eye tracking, the tracker is placed near the object to be tracked. This object is essentially stationary and the respondent will be positioned in front of the system in a stationary position. This setup is especially practical and precise for any observations of two-dimensional structures. A mobile eye tracker is a head mounted system, which is fitted like glasses near the eyes of the respondents. They can be useful when observing an object that has a three-dimensional structure or when the respondent needs to freely move around.
Using eye tracking in human behavior research unlocks many interesting measures, such as attention, interest and arousal. What exactly do we find interesting in videos and pictures? What elicits our attention? These are only a few of many questions that can be answered by using eye tracking with the appropriate software.
More insights about measurements, differences and dis-/advantages of stationary and mobile eye tracking will be discussed in our next blog posts about eye tracking. Stay tuned! Contact the iMotions team to find out how you can get started.