Fig. 1. Elements of eye-tracking analysis.

In [37], Zics taken heed of two still significant and relevant claims concerning the relationship between attention and eye movements. Both of them indicate an importance of the eye in processing information and give significance to the underlying voluntary processes of the mind as the control mechanism of attention or imagination.



The first claim comes from Hermann von Helmholtz. He stated that the eye’s optical characteristics and information gathering is rather poor. Therefore, vision is only possible with some form of unconscious inference that makes sense of the information based on prior experiences of the world [9]. Studying the relationship between eye movements and visual attention, Von Helmholtz discovered the phenomena of “covert attention”, which explained that visual attention is not always where eye fixation is directed to. One can attend to stimuli without shifting visual focus. The second claim comes from William James. He provided an explanation of a different aspect of visual experience. He claims that attention and imagination are directly related. When attention does not regulate one’s sense organs it consists in imagining the things or actions that one is attending to, or looking for [13].



• In the analysis of eye-movements, the physiological capacities of the eye play an important role [37]. The size of the visual field is limited. It can be divided into:

• “parafoveal vision”, between 2 and 10 degrees off centre, responsible for low-resolution compressed information,



• “peripheral field”, more than 10 degrees off centre.

The visual field cannot be processed from one single fixation (lasting between 180 and 275 ms), as a result of the limited acuity of the retina. Therefore, rapid eye movements (saccades) are necessary to bring the retinal image of an object of interest to lie on the fovea (lasting between 10ms and 100ms). Attention initially assigns a target before saccade eye movements happen. During saccades, vision is dormant and new information is acquired only during fixation [12].



Zics in [37], takes notice that although there is a long history of research on the relationship between eye movement and aesthetic experience, the methods applied often reduce the viewer’s act to a mechanistic agency and, as such, makes the aesthetic claims of such work questionable. She critically assessed this fact and quoted some examples showing that psychological accounts have subsequently been popular in the study of eye movement research, among others, Alfred L. Yarbus who used a scanpath (a graph of saccades and fixations) and the visual recording of eye movements (fixations and saccades) to study complex scenes to identify mainly task-dependent patterns of fixations [35] and Daniel Berlyne who used a concept of “diversive-specific” behavioral patterns of the viewer [1]. According to Zics, it is argued that real-time dynamic processes allow a meaningful exploitation of eye movement for particular aesthetic production.



In [14], Josephson and Holmes taken heed of the significance of scanpath theory. Noton and Stark’s scanpath theory [24] predicts that a subject scans a new stimulus during the first exposure and stores the sequence of fixations in memory as a spatial model, so that a scanpath is established. When the subject is reexposed to the stimulus, the first few eye movements tend to follow the same scanpath established during the initial viewing of the stimulus, which facilitates stimulus recognition. Research also indicates that when a subject is presented with a blank screen and told to visualize a previously seen figure, the scanpath is similar to when he or she viewed the figure [32]. Noton and Stark claimed that the internal representation of a pattern in memory is a network of features and attention shifts, with a habitually preferred path through the network, corresponding to the scanpath. During recognition, this network is matched with the pattern, directing the eye or internal attention from feature to feature of the pattern [24].



In [30], Saarinen, Laine-Hernandez and Saarelma taken heed of the influence of image content levels and looking type on eye movements. Visual perception is based on the collaboration between the eyes and the brain. Eyes collect visual stimuli from a scene and the brain forms visual percepts and interprets eye movements. During observations of visual scenes, the gaze shifts from place to place with rapid voluntary eye movements (saccades) and vision collects information with static fixations, which occur between saccades. The most interesting areas of the scene are observed first and then the gaze goes through the same areas again. Hence, the least interesting areas are not observed at all and the most interesting areas get the attention over and over again [35]. According to Kahneman [17], eye movements can be classified into three categories with respect to viewing situation: spontaneous looking (free viewing of a visual scene), task-relevant looking (viewing with a certain task in mind), and orientation of thought looking (a person is concentrated on something else than the visual scene). Visual content consists of syntactic and semantic levels. Syntactic levels define the visual elements and are in close relation to visual perception. Semantic levels are concentrated on visual concepts and they define the meanings of the visual elements and of their arrangements. Factors that influence observation at the syntactic level include contrast, size, shape, color, and

movement. Interesting semantic level elements include different human and animal shapes, as well as figures that do not fit in the picture.



4. From a layman to a connoisseur of art





The eyes can be trained to seek out aesthetic qualities of visual compositions and that this aspect of formal art training can directly influence a trained viewer's perceptual analysis and appreciation of visual compositions [24]. In [15], Jung claimed that in general, the significance and beauty of art are only apparent to those who can see and are trained in viewing. According to this claim, different questions on the relationship between training and the perception of art can be posed [24]. For example, how does formal art training influence perception? Does such art training result in changes in how visual compositions are scanned and what type of information is processed during perceptual analysis? How does the scanned information contribute to the formation of aesthetic judgments? The use of eye-movement recording as a method of studying the role that the eyes play in analyzing and interpreting visual compositions is one of research topics. Buswell [5] and Brandt [4] indicated important differences in eye-fixation patterns between art-trained and untrained viewers. A number of researches tried to quantify the nature of these differences, for example, Yarbus [35], Molnar [22], Locher and Nodine [20], [21].

Fig. 2. Comparison on scanpaths: (a) expert – connoisseur,

(b) expert – teacher of art, (c) novice - student

​

Picture perception in artists and laymen has been compared in several studies on the assumption that artists view the world differently from others, for example, Putko found that artists employed different cognitive interpretations of 16 well-known paintings [27], Nodine, Locher, and Krupinski found that artistically untrained viewers tended to spend more time viewing individual objects than relationships among elements in paintings [24]. Mentioned authors used descriptive eye-movement data. Other authors have examined different eye-fixation patterns in artists and non-artists viewing pictures, for example, Antes and Kristjanson found that eye-movement parameters alone could differentiate artists from non-artists by fixation densities on less important aspects of paintings [1], Zangemeister, Sherman and Stark found that artists and sophisticated viewers used a more global scanning strategy than artistically untrained participants when viewing abstract pictures [36]. 

​

In [24], Nodine, Locher, and Krupinski concluded that compositional design influences how trained viewers look at paintings by supplementing the viewer's perceptual strategy in guiding attention to structural relationships among pictorial elements that express narrative themes. An individual's aesthetic judgments are based on the perceived structure among pictorial elements (lines, shapes, colors, surfaces) and the interpreted narrative theme.





4. The characteristics of didactic computer systems based on eye-tracking technology



The eye-tracking system constitutes one of the main parts of didactic interactive computer systems. A principle of operation is based on the optical measurement. The infrared rays come from the system to eyes for tracing the eye-movements. Next, the infrared rays are reflected to the system from eyes and the data of eye-movements are recorded. The eyes are controlled by human brain where cognitive processes are produced. 

​

The eye-movement data can be recorded using two most common formats such as Heat Map and Sequenced Gazing with circle of concentration. In case of Heat Map, the track of eye is recorded as illumination and intensity of infrared light rays. In case of Sequenced Gazing, the eye tracks are recorded as numbered circles with their areas indicating the time duration of eye’s gazing in those areas, respectively. The measurement of eye-movements is now common in many diverse areas of cognitive psychology. In general, the measurements consider each eye movement event independently. However, the pattern of inspection can only be revealed by considering a sequence of successive fixations. These patterns are sometimes referred to as scanpaths or scan patterns [10]. Functioning of the module of didactic correction is based on real-time supervision of deviations of scanpaths of a learning person from pattern scanpaths (artist-expert’s scanpaths of image analysis). Several different basic methods for comparing scanpaths are reviewed in [33]. The main criteria for evaluating methods for comparing scanpaths take into consideration whether they appropriately capture the degree of similarity between different scanpaths and the ease of testing this statistically.

Figure 3. A system structure [1]



​5. Conclusions



Interactive computer systems based on eye-tracking technology are only the first step towards modernizing the means supporting didactics of visual art perception. Conducted research indicates functional and topographical differences between two groups, artists and non-artists, during the performances of visual perception and imagery of paintings were presented by means of EEG (Electroencephalography) phase synchrony analysis (cf. [1]). EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain [23]. The analysis of phase synchrony from EEG signals yields new information about the dynamical co-operation between neuronal assemblies during the cognition of visual art. Therefore, it is necessary to equip interactive computer systems with additional correction loops, which functionality is based on analysis of the EEG biosignals. Combining eye-tracking and EEG is one of the most fascinating and challenging problems (cf. [7]). Scientists are dealing with this problem to close the gap between the psychological mental processes leading to the sensations we experience in everyday life and their underlying physiological biochemical processes. They are trying to understand perception, the process by which our brain makes sense out of the signals coming from our senses. Eye-tracking alone is not sufficient because provides only psychophysical data. It provides valuable information about the gaze location, but does not provide any information about neuronal activity. On the other hand, EEG, measuring neuronal activity in humans, does not directly provide information about the gaze position. For this reason, projects combining EEG and eye-tracking into one common setup have been started by scientists. 



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