How Does Eye Tracking Detect the Object of Visual Attention?
A recent Eye Tracking Update post detailed the basic anatomy of the eye and the two primary types of vision, foveal and peripheral. To continue the discussion on eye biology and how it relates to eye tracking technology, let’s take a look at the behavior that brings the two together: eye movement. The majority (about 94%) of our vision falls in the peripheral region, which is only good for producing a blurred image of surroundings for detecting movement and contrast. Detailed visual data about surroundings cannot be completely registered by the brain unless it is observed through the foveal region of the visual field, which only constitutes about 6% of our vision. Shifting the foveal region over various points of interest is the reason eyes move.
When something that warrants further examination is detected in the peripheral vision, our eyes will move to place the foveal region over the object or location, bringing it into focus and allowing for more detailed mental processing. In other words, we move the central focusing region of our eyes to the object that catches our visual attention in order to get a clearer, higher resolution image of the point of interest. This is called a fixation; the eye pauses on a specific spot in the visual field so that it can be processed more clearly by the brain. The rapid eye movements in between fixations are called saccades, and both can be detected by eye tracking devices.
Eye tracking technology monitors and traces pupil movement, which consequently allows for the identification of the object of visual attention by locating the direction of gaze. This can be very useful information and is the primary function of eye tracking for many research applications. For instance, using eye tracking to identify the objects that attract visual attention in advertisements can indicate to advertisers whether the intended elements are receiving the desired level of interest. Another example could be using eye tracking during a driving simulation to monitor visual attention while talking on a cell phone. Being able to identify an object of visual attention is the reason eye tracking has been said to give an observer a view into the mind of the user.
An Introduction to Eye Tracking : Part 2 – Why do our eyes move?