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What Do Eye Movements Tell Us About Objects and Scene Perception?
By William Schwieger

Modern, non invasive, eye tracking technology has allowed researchers to study eye movements in new and exciting ways. Scientists are able to study the way in which people scan an object and observe a scene. Eye trackers are able to detect saccades, or movements of the eye, that are marked by pauses in movement. These pauses are called fixations, and they mean that a person is attending that part of the object or scene. Saccades and fixations are mapped by eye trackers, and researchers can study how people scan objects and scenes for information.

When scanning an object, eye movements can tell us important things about an object. Since the human eye is designed to take in visual information in bits and pieces, via our high resolution fovea, scientists can study both the positions of the eye, and how long a particular fixation was held for. This information can help scientists to understand how objects are processed in our perceptual system. The Gestalt Laws of Organization, also called Pragnanz, indicate that we perceive objects as a whole by identifying features of the object. Studies of the brain have indicated that we have structures that are dedicated to identifying specific stimuli in the visual field. Recognition occurs in the brain only when we are able to match the observed parts of the object to a memory of that object. By having participants in a study visually scan and recognize an object with a head mounted eye tracker, scientists can determine what features are important for recognition of objects in space.

Scene perception is another area of research that is studied with the use of eye tracker devices. Scenes are made up of many objects within are visual field, and are observed in a very unique way through eye movements. Since our eyes are not designed to take in a “whole picture”, they must observe a scene by scanning it, and taking in the most important parts. Eye trackers are able to observe the scan path of our eyes in order to determine what the important parts are of that scene. Scientists have found that certain factors contribute to the perceived visual importance of elements of a scene. Bright colors, high contrast, and visible orientations all contribute to what is known as stimulus salience. Stimulus salience is a good predictor of the parts of a scene that will be fixated upon by an observer, and saliency maps can be created to describe this effect. When visually scanning a scene, fixation points are not random, and people often follow the same scan path as others.

Scene perception gets even more complex when we consider scene schemas. Once familiar with a scene, humans are able to distinguish unique features from a common scene. This means that people will not actively scan an entire scene when they are already familiar with it, instead they can focus on an object of interest (like a painting or a face), or pick out something that is out of place. Scene schemas are also important important in moving from one place to another because it helps people to recognize the similarities between common places.

Eye movements have been studied with eye trackers, and have given us a wealth of knowledge about how humans perceive the visual world around them.