| ISLE | Chapter 9
| Scanning
Typically, we attend to a particular location in space by directing our gaze to that location. Thus, when reading, you are directing your gaze at the words on the page, and when you glance up at the baseball game, you direct your gaze to the television screen. In almost all situations, what is being represented in our foveae is what we are attending to. If our attention shifts, so does our gaze. When one changes one’s attention from the textbook to the baseball game, it is usually accompanied by a change in the direction of gaze. This movement of our eyes makes sense given that the best acuity is found on our foveae (recall Chapter 3). Even within a scene, we usually have to move our eyes around the scene, or scan the scene to take it all in. Let us try an example, find one of the authors in this photograph below. Unless you are modestly lucky you have to move your gaze around the picture to find this author. The main way you look around the image is to make saccades. Researchers use sophisticated methods to track eye movements. They look for where the eyes pause between saccades, the fixations, because during saccades, the eyes move too fast to see clearly (e.g., Zanos, Mineault, Guitton, & Pack, 2016).
Use this illustration to track your attempts to scan an image. Read the question, and then scan the image by moving your mouse or finger over the image. The computer will reveal what is below your mouse or finger. After a period of time, the computer will stop tracking and show you how you tracked the image.
Photo credit: Margaret Krantz.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
On the Illustration tab, you can adjust the parameters and start a simulation of dark adaptation.
Below is a list of the ways that you can use the illustration. The settings include the following:
Choose a Preselected Image: select from a pre-selected list of images.
Each will ask you a particular task to accomplish list above under the word 'Question'.
How long to sample: use this slider to determine how long
the sample period will be.
Show sample points select to have small red dots show each point in time
your position was sampled in addition to green dots showing your pauses as simulated fixations.
Use Your Own Image: allows you to upload your own image. You will
have to determine your own task to scan the image.
Start: start the sampling process.
Pressing this button restores the settings to their default values.