Gaze-contingency paradigm

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Within computer technology, 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.

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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 them. Because the display updates in response to the observer's eye movements, the gaze-contingency paradigm can be classified an interactive eye-tracking application. [1]

Background

Over the past century, the way the eyes move in human activities as diverse as playing sport, viewing works of art, piloting aircraft, exploring visual scenes, recognizing face or facial expressions, [2] [3] reading language, and sight-reading of music, [4] has revealed some of the ocular and psychological mechanisms involved in the visual system. The gaze-contingent techniques aim to overcome limitations inherent to simple eye-movement recording. Indeed, due to an imperfect coupling between overt and covert attention, [5] [6] [7] it is not possible to exactly know which visual information the viewer is processing based on the fixation locations. By controlling precisely the information projected in different parts of the visual field, the gaze-contingent techniques permit to disentangle what is fixated and what is processed.

The technical principle of the paradigm involves a computer interfaced with both an eye-movement tracking system (eye-tracker) and a display of the visual stimulus. Successful gaze-contingency requires a fast computer, a display with a high refresh rate, and an eye tracker with low latency. [8] [9] In gaze-contingent displays, the stimulus is continuously updated as a function of the observers' current gaze position; for instance, in the moving window paradigm, [10] [11] [12] observers can see the scene only through a central hole, giving the sensation of seeing through a telescope.

Therefore, the gaze-contingent technique is a powerful method to control for the visual information feeding the visual system and to isolate information use.

Techniques

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 [13] [14] 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 [15] 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, [16] [17] [18] 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. [19] [20] 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. [21] The parafoveal magnification paradigm [22] 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.

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. Parafoveal magnification paradigm.jpg
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.

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 [23] [24] ), the nature of the extrafoveal information extracted during a fixation, for instance orthographic and phonological information (boundary paradigm) [25] [26] [27] or the relative influence of attention versus visual acuity drop-off in the perceptual span (parafoveal magnification paradigm [28] ).

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, [29] [30] and others have made the entire task display disappear whenever the observers look away from a specific task-relevant area. [31]

Applications

The gaze-contingent technique has been adapted in other tasks than reading. The moving window paradigm has been used to study the effect of culture in face recognition for example. [32] The moving mask paradigm has been used in visual learning [33] or visual search of animals in natural visual scenes. [34]

The various gaze-contingent techniques has given eye-movement researchers the ability to observe the processing of visual input in much greater detail (particularly its temporal characteristics), the perceptual span, and the nature of central versus peripheral processing in reading.

See also

Related Research Articles

<span class="mw-page-title-main">Attention</span> Psychological process of selectively perceiving and prioritising discrete aspects of information

Attention is the concentration of awareness on some phenomenon to the exclusion of other stimuli. It is a process of selectively concentrating on a discrete aspect of information, whether considered subjective or objective. William James (1890) wrote that "Attention is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration, of consciousness are of its essence." Attention has also been described as the allocation of limited cognitive processing resources. Attention is manifested by an attentional bottleneck, in terms of the amount of data the brain can process each second; for example, in human vision, only less than 1% of the visual input data can enter the bottleneck, leading to inattentional blindness.

<span class="mw-page-title-main">Saccade</span> Eye movement

A saccade is a quick, simultaneous movement of both eyes between two or more phases of fixation in the same direction. In contrast, in smooth-pursuit movements, the eyes move smoothly instead of in jumps. The phenomenon can be associated with a shift in frequency of an emitted signal or a movement of a body part or device. Controlled cortically by the frontal eye fields (FEF), or subcortically by the superior colliculus, saccades serve as a mechanism for fixation, rapid eye movement, and the fast phase of optokinetic nystagmus. The word appears to have been coined in the 1880s by French ophthalmologist Émile Javal, who used a mirror on one side of a page to observe eye movement in silent reading, and found that it involves a succession of discontinuous individual movements.

In the study of vision, visual short-term memory (VSTM) is one of three broad memory systems including iconic memory and long-term memory. VSTM is a type of short-term memory, but one limited to information within the visual domain.

Iconic memory is the visual sensory memory register pertaining to the visual domain and a fast-decaying store of visual information. It is a component of the visual memory system which also includes visual short-term memory (VSTM) and long-term memory (LTM). Iconic memory is described as a very brief, pre-categorical, high capacity memory store. It contributes to VSTM by providing a coherent representation of our entire visual perception for a very brief period of time. Iconic memory assists in accounting for phenomena such as change blindness and continuity of experience during saccades. Iconic memory is no longer thought of as a single entity but instead, is composed of at least two distinctive components. Classic experiments including Sperling's partial report paradigm as well as modern techniques continue to provide insight into the nature of this SM store.

<span class="mw-page-title-main">Vision span</span> Arc of accurate visual perception

Vision span or perceptual span is a controversial concept referring to the angular span, within which the human eye has sharp enough vision to perform an action accurately. The visual field of the human eye spans approximately 120 degrees of arc. However, most of that arc is peripheral vision. The human eye has much greater resolution in the macula, where there is a higher density of cone cells. The macula has a diameter of about 16 degrees of the retina. The field of view that is observed with sufficient resolution to read text typically spans about 6 degrees of arc, which is wide enough to allow a clear view of about five words in a row when printed text at ordinary size is held about 50 centimeters from the eyes. Regarding face processing, the field of view with a sufficient amount of information in order to recognise faces accurately spans about 7° which represents about 45% of a face. The brain creates the illusion of having a greater visual span by automatically and unconsciously moving the center of vision into any area of interest in the field of view.

<span class="mw-page-title-main">Eye tracking</span> Measuring the point of gaze or motion of an eye relative to the head

Eye tracking is the process of measuring either the point of gaze or the motion of an eye relative to the head. An eye tracker is a device for measuring eye positions and eye movement. Eye trackers are used in research on the visual system, in psychology, in psycholinguistics, marketing, as an input device for human-computer interaction, and in product design. In addition, eye trackers are increasingly being used for assistive and rehabilitative applications such as controlling wheelchairs, robotic arms, and prostheses. Recently, eye tracking has been examined as a tool for the early detection of autism spectrum disorder. There are several methods for measuring eye movement, with the most popular variant using video images to extract eye position. Other methods use search coils or are based on the electrooculogram.

Inattentional blindness or perceptual blindness occurs when an individual fails to perceive an unexpected stimulus in plain sight, purely as a result of a lack of attention rather than any vision defects or deficits. When it becomes impossible to attend to all the stimuli in a given situation, a temporary "blindness" effect can occur, as individuals fail to see unexpected but often salient objects or stimuli.

<span class="mw-page-title-main">Eye movement</span> Movement of the eyes

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<span class="mw-page-title-main">Change blindness</span> Perceptual phenomenon

Change blindness is a perceptual phenomenon that occurs when a change in a visual stimulus is introduced and the observer does not notice it. For example, observers often fail to notice major differences introduced into an image while it flickers off and on again. People's poor ability to detect changes has been argued to reflect fundamental limitations of human attention. Change blindness has become a highly researched topic and some have argued that it may have important practical implications in areas such as eyewitness testimony and distractions while driving.

Microsaccades are a kind of fixational eye movement. They are small, jerk-like, involuntary eye movements, similar to miniature versions of voluntary saccades. They typically occur during prolonged visual fixation, not only in humans, but also in animals with foveal vision. Microsaccade amplitudes vary from 2 to 120 arcminutes. The first empirical evidence for their existence was provided by Robert Darwin, the father of Charles Darwin.

Visual search is a type of perceptual task requiring attention that typically involves an active scan of the visual environment for a particular object or feature among other objects or features. Visual search can take place with or without eye movements. The ability to consciously locate an object or target amongst a complex array of stimuli has been extensively studied over the past 40 years. Practical examples of using visual search can be seen in everyday life, such as when one is picking out a product on a supermarket shelf, when animals are searching for food among piles of leaves, when trying to find a friend in a large crowd of people, or simply when playing visual search games such as Where's Wally?

<span class="mw-page-title-main">Eye movement in music reading</span> Role of the eyes in reading music

Eye movement in music reading is the scanning of a musical score by a musician's eyes. This usually occurs as the music is read during performance, although musicians sometimes scan music silently to study it. The phenomenon has been studied by researchers from a range of backgrounds, including cognitive psychology and music education. These studies have typically reflected a curiosity among performing musicians about a central process in their craft, and a hope that investigating eye movement might help in the development of more effective methods of training musicians' sight reading skills.

Eye movement in reading involves the visual processing of written text. This was described by the French ophthalmologist Louis Émile Javal in the late 19th century. He reported that eyes do not move continuously along a line of text, but make short, rapid movements (saccades) intermingled with short stops (fixations). Javal's observations were characterised by a reliance on naked-eye observation of eye movement in the absence of technology. From the late 19th to the mid-20th century, investigators used early tracking technologies to assist their observation, in a research climate that emphasised the measurement of human behaviour and skill for educational ends. Most basic knowledge about eye movement was obtained during this period. Since the mid-20th century, there have been three major changes: the development of non-invasive eye-movement tracking equipment; the introduction of computer technology to enhance the power of this equipment to pick up, record, and process the huge volume of data that eye movement generates; and the emergence of cognitive psychology as a theoretical and methodological framework within which reading processes are examined. Sereno & Rayner (2003) believed that the best current approach to discover immediate signs of word recognition is through recordings of eye movement and event-related potential.

<span class="mw-page-title-main">Foveated imaging</span>

Foveated imaging is a digital image processing technique in which the image resolution, or amount of detail, varies across the image according to one or more "fixation points". A fixation point indicates the highest resolution region of the image and corresponds to the center of the eye's retina, the fovea.

Visual perception is the ability to interpret the surrounding environment through photopic vision, color vision, scotopic vision, and mesopic vision, using light in the visible spectrum reflected by objects in the environment. This is different from visual acuity, which refers to how clearly a person sees. A person can have problems with visual perceptual processing even if they have 20/20 vision.

Perceptual learning is learning better perception skills such as differentiating two musical tones from one another or categorizations of spatial and temporal patterns relevant to real-world expertise. Examples of this may include reading, seeing relations among chess pieces, and knowing whether or not an X-ray image shows a tumor.

Chronostasis is a type of temporal illusion in which the first impression following the introduction of a new event or task-demand to the brain can appear to be extended in time. For example, chronostasis temporarily occurs when fixating on a target stimulus, immediately following a saccade. This elicits an overestimation in the temporal duration for which that target stimulus was perceived. This effect can extend apparent durations by up to half a second and is consistent with the idea that the visual system models events prior to perception.

<span class="mw-page-title-main">Parafovea</span>

Parafovea or the parafoveal belt is a region in the retina that circumscribes the fovea and is part of the macula lutea. It is circumscribed by the perifovea.

Visual spatial attention is a form of visual attention that involves directing attention to a location in space. Similar to its temporal counterpart visual temporal attention, these attention modules have been widely implemented in video analytics in computer vision to provide enhanced performance and human interpretable explanation of deep learning models.

Binocular switch suppression (BSS) is a technique to suppress usually salient images from an individual's awareness, a type of experimental manipulation used in visual perception and cognitive neuroscience. In BSS, two images of differing signal strengths are repetitively switched between the left and right eye at a constant rate of 1 Hertz. During this process of switching, the image of lower contrast and signal strength is perceptually suppressed for a period of time.

References

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