![]() A small camera at the base of the computer zooms in on one (or both) of the eyes as diodes emit near-infrared light (people cannot perceive light at that wavelength, so they experience no discomfort). In a typical experiment-say, to study reading or attention-a participant sits in front of a computer with her head on a chin rest. Nowadays researchers rely on the way the cornea reflects light to chart the rotation of the eyeballs. Other early contraptions used combinations of contact lenses, suction cups, embedded mirrors and magnetic field sensors to triangulate the focus of the viewer's attention. To minimize irritation, the eyeball was anesthetized with cocaine, and the head was held in place using clamps and a bite bar. A lever was attached to the eyecup and to the lever a pen, which made contact with a rotating drum as the participant read. It was a rather invasive apparatus, involving a plaster cup, worn on the eyeball, with a tiny hole through which the subject could see. Early in the 20th century psychologist Edmund Huey of the Western University of Pennsylvania (now called the University of Pittsburgh) created a device that could correlate eye movements with the words on a page as someone reads. Hence the quest for hardware that can track every movement of the eyes, no matter how fleet. ![]() That herky-jerky motion posed a puzzle for investigators: How, despite the constant movement, do we experience vision as stable? So we move our eyes constantly to bring new pieces of information into central focus. Indeed, the part of the visual field that delivers a sharp image is about the size of a dime held at arm's length, with quality falling off sharply toward the periphery. The main reason for the jerky behavior is that our visual sweet spot is very small. The short, still periods are known as fixations, and the quick jumps are called saccades. In most instances, our eyes stay relatively still for extremely short periods (usually around a third of a second), followed by rapid jerks until they alight on their next target. Despite our subjective experience of vision as a smooth sweep across a stable landscape, the movement of our eyes is anything but steady. The experimenter would sit across from a person and take notes about the behavior of the subject's eyes.Įarly findings were surprising. Initially eye tracking was a matter of simple observation. Clinicians were also interested in how eye movements relate to disorders involving vision problems, such as vertigo. Researchers developed eye tracking primarily to learn about basic visual processing (say, how we meld independent streams from each eye into a single mental image). Marketers are eager to tap into our gaze patterns, too, with implications for privacy. ![]() Our new understanding of eye movements is also spurring development in a host of industries, especially gaming, computers and health care. Eye tracking can reveal whether we are processing the things in front of us or are mentally adrift, whether we recognize a face or have never encountered it before-or whether we did encounter it but then forgot. Not so incidentally, as the technology advances, researchers are learning ever more about the workings of our eyes and unobservable aspects of the mind: our thoughts and mental focus and the pathways into our consciousness. Interactions with devices equipped with eye-tracking sensors and software can seem intuitive and effortless, as if our gadgets are reading our minds. ![]() Loosely defined, eye tracking refers to any technology that can monitor the direction of our gaze and the behavior of our eyes, in the process generating data that give clues to our intentions. It is the real-world spinoff from the burgeoning field of eye tracking. And from the time you sit down at your desk in the office until you make your final Xbox feint, you carry out most of these interactions without using your hands or even your voice but simply by moving your eyes.įar from being science fiction, the technology to support such a seamless merging of our digital and physical lives already exists. You assume an identity and traverse the virtual landscape, evading some characters, blasting others. When you get to your living room, you turn on your video game console. As you're driving home, something about the car in the next lane distracts you, but a gentle alert reminds you to pay attention to the road. You read your latest messages and write a few yourself, then log out. You log on to your computer, navigate the desktop, open a browser, sign in to your e-mail account. You're in your office near the end of the day, preparing to head home.
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