What is eye-tracking? (1 hour)

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Eye-tracking is a technique that has many uses. In this module we'll talk about two of them. First, though, we need to see what eye-tracking actually is. Do the activities below to learn about what the eye-tracking method is.

(I recommend you complete the exercises about self-paced reading in the "Reaction times" module before completing this task.)

You probably have already learned about one way we can study how people read: self-paced reading.

Think about how a self-paced reading experiment works. (If you don't remember, you can go back to the "Reaction times" module and do the self-paced reading garden path experiment again.) Then answer the following two questions:

  1. Describe what a self-paced reading experiment is—how it works, and what it measures.
  2. Can you think of any reasons why results from a self-paced reading experiment might not be realistic, or might not be a good measure of how people naturally read? e.g., are there any important differences between how natural reading works and how self-paced reading works?

Here are a couple potential problems with self-paced reading that I could think of:

  1. Button-pressing is unnatural. In normal reading in real life, you don't have to press a button to read each next word. When you do self-paced reading, maybe the act of constantly pressing the button distracts you a little bit and changes the way you read.
  2. No backtracking. When you read normally in real life, you can look back and re-read things (for example, maybe you read a few sentences and then realize you hadn't fully understood something from earlier, so you look back to read it again). But in the self-paced reading experiment we did, there's no way to go back; once you click the button and go to the next word, the previous words are gone.

These are two possibly important ways that self-paced reading is different than regular reading. There are probably other important differences, too; did you think of any other ones that I didn't mention here?

In any case, because of these issues, you might be skeptical about self-paced reading: do results from self-paced reading experiments really teach us about how normal reading happens?

One way to address that question is to use eye-tracking. Eye-tracking is a special method that uses some special software and a special camera to figure out where people are looking on a screen. In an eye-tracking experiment, you show the whole sentence on the screen (instead of showing one word at a time like you do in self-paced reading) and let a person read it. While the person reads it, a camera (usually just under the screen, or on a special hat that a person wears to hold a camera near their eye) records the person's eyeball. Using math (especially trigonometry—because the space between the screen, the camera, and the person's eye makes a triangle) the camera can figure out what place on the screen the person's eyes are looking at. Using this, the eye-tracker can figure out how long a person takes to read each word.

As I mentioned, there are two kinds of eye-tracking cameras: cameras that sit on the table usually below the screen (these are sometimes called "remote" eye-trackers), and cameras that a person wears on a special kind of hat (these are sometimes called "head-mounted" eye-trackers). Search online (using Google Images or something similar) and find a picture of what a remote eye-tracker looks like and a picture of what a head-mounted eye-tracker looks like.

To get a sense for how people's eyes move when they are reading, watch three brief videos on YouTube:

After having watched those, please describe how people's eyes move when they read. Some things you can address in your description:

When you have finished these activities, continue to the next section of the module: "Using eye-tracking to study how people read".


by Stephen Politzer-Ahles. Last modified on 2021-05-14. CC-BY-4.0.