page_title: Gaze-contingency paradigm
section_title: Techniques
hierarchical_section_title: Gaze-contingency paradigm / Techniques
caption_attribution_description: English: Graphical depiction of the parafoveal magnification (PM) paradigm. The location of each fixation is indicated with an arrow and the corresponding display for that fixation is represented. Consecutive lines represent the chronological order of fixations.
context_page_description: The gaze-contingency paradigm is a general term for techniques allowing a computer screen display to change in function depending on where the viewer is looking. Gaze-contingent techniques are part of the eye movement field of study in psychology.
  From a system analysis point of view, eye-tracking applications should be distinguished from diagnostic or interactive system. In diagnostic mode, the eye tracker provides data about the observer’s visual search and attention processes. In interactive mode, the eye-tracker is used as an input device. From a general point of view, an interactive system responds to the observer’s actions and interacts with him. Because the display updates in response to the observer's eye movements, the gaze-contingency paradigm can be classified an interactive eye-tracking application.
context_section_description: The gaze-contingent technique is the basis of various experimental paradigms, each of them allowing to investigate specific cognitive processes.
  In the moving window paradigm only the part of the visual field around the gaze location (foveal information) is displayed normally, the surrounding part of the visual field (extrafoveal and peripheral information) being altered (removed for visual scenes or replaced by chains of X in reading).
  The moving mask paradigm is a reverse technique in comparison with the moving window paradigm. It dynamically obscures central vision (or replaces letters with X in reading), permitting only extrafoveal information use. 
  In the boundary paradigm, an extrafoveal prime (a homophone in reading for example) is replaced by the target stimulus when the eyes cross an invisible boundary around the target area. In a related technique, the display can be updated when the gaze moves at a speed higher than a specified velocity threshold, ensuring that the display updates during a saccade. This velocity thresholding technique is used to prevent the observer from noticing the changes made to the display, because saccadic suppression blocks visual processing during saccades.
  The parafoveal magnification paradigm compensates for how visual acuity drops off as a function of retinal eccentricity. On each fixation and in real time, parafoveal text is magnified to equalize its perceptual impact with that of concurrent foveal text.
   
  In the language domain this method has been successfully used in natural reading. The study of eye movements in reading allowed researchers to map out the perceptual span (moving window paradigm), the nature of the extrafoveal information extracted during a fixation, for instance orthographic and phonological information (boundary paradigm) or the relative influence of attention versus visual acuity drop-off in the perceptual span (parafoveal magnification paradigm).
  Gaze-contingent techniques can also be used to ensure compliance with other aspects of a task. For example, some researchers have required that observers look at a specific location and press a button before the task begins, and others have made the entire task display disappear whenever the observers look away from a specific task-relevant area.
caption: Parafoveal magnification paradigm: Graphical depiction of the parafoveal magnification paradigm (Miellet et al., 2009).  The location of each fixation is indicated with an arrow and the corresponding display for that fixation is represented.  Consecutive lines represent the chronological order of fixations.
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