The visual search abilities of radiologists are systematically trained due to the specifics of their professional tasks. We investigated whether the visual-motor performance of radiologists, residents and students varied when searching non-medical targets on the volumetric display. As a result, no significant differences were found in the correct response rate among three groups. However, the total number of interactions was considerably higher for the resident radiologists and medical students comparing to the experienced radiologists. Our results suggest that the radiological experience does not interfere with the outcome in the developed visual search task, but may be reflected in motor behavior.
In natural viewing, numerous depth cues are available to the visual system, but their significance varies considerably depending on the viewing distance. How is it reflected in the outcome of depth judgements? We have designed a psychophysical experiment with a limited number of depth cues to examine distance-related changes in the correct response rate and time. Twenty young adults evaluated relative depth of stimuli in physical space. Each time four constant angular size achromatic stimuli were presented on a volumetric multi-planar display. One of these stimuli was demonstrated closer to the observer comparing to others. The experiment followed the four-interval forced-choice procedure. On any given trial, observers determined which one of four stimuli was located closest to them. The nine viewing distances ranged from 0.5 m to 2.5 m. Overall, the depth judgements were correct and fast at the close viewing distances. However, the correct response rate dropped markedly at 1.0 m distance and continued declining gradually at larger distances. The average response time experienced the linear growth with increasing distance. In total, we showed that the relative depth judgements based on binocular depth cues changed the most at the viewing distances that exceeded 1.0 m, as well as the response time and correctness were affected to varying degrees.
In diagnostics, radiologists search for anatomical abnormalities through generated three-dimensional data on flat displays. Professionals are required to scroll repeatedly through image stacks forth and back, as well as remember a broad amount of visual information. This process leads to working memory overload and decreased search outcome. In contrast, a volumetric multi-planar display includes many planes, which makes possible to visualize data in a true physical depth. Thus, theoretically, it can facilitate the visual search performance in diagnostics and lessen the necessity for repeated scrolling. Therefore, our work aims to explore practically the extent to which the visual search is effective, as well as deliver evidence on the scrolling strategy through image stacks when data are shown on many display planes. Visual search set consisted of constant angular size stimuli presented on ten out of twenty display planes in two depth segments. Participants searched for a target with varying target-distractor similarity within trials. All ten images were presented simultaneously in the beginning of each trial and participants scrolled freely through them. In the result, target discriminability affected significantly the correct response rate and time, as well as search behavior was consistent with the physical design of stimuli set. In more detail, the number of moves through image stack almost doubled when the target-distractor similarity increased and, overall, participants skipped searching repeatedly already seen images. The developed visual search task is suggested for implementation in studies of visual perception and search behavior in threedimensional displays.
In medical imaging, large sets of two-dimensional images are used for evaluating anatomical structures. Observers experience high cognitive load due to necessity of memorizing information and data is not seen in a real volume. A volumetric multi-planar display is a promising technology that can eliminate above mentioned issues by producing images in a real three-dimensional space. Therefore, the goal of our study was to investigate how well individuals perceived a difference in spatial localization of visual stimuli and describe its impact on visual search performance in three-dimensional digital space. Participants searched for a target stimulus which was located closer to the observer comparing to other stimuli in different depth segments of a display and provided subjective evaluation of the task difficulty. The results revealed that on average visual attention could be deployed without significant differences on all four depths segments in terms of response time and quality. But at the same time, eccentricity of stimuli influenced considerably the performance which can be related to higher cognitive load due to limitation of visual acuity and attention in the peripheral visual field. To be added, subjective evaluation of perceived task difficulty matched well response time and accuracy in visual search. The obtained results leaded to the conclusion that spatial layout of stimuli in horizontal and vertical dimension had a bigger impact on visual search performance comparing to the third dimension on a volumetric multi-planar display.
Instead of selecting arbitrary elements our visual perception prefers only certain grouping of information. There is ample
evidence that the visual attention and perception is substantially impaired in the presence of mental fatigue. The question
is how visual grouping, which can be considered a bottom-up controlled neuronal gain mechanism, is influenced. The
main purpose of our study is to determine the influence of mental fatigue on visual grouping of definite information –
color and configuration of stimuli in the psychophysical experiment. Individuals provided subjective data by filling in
the questionnaire about their health and general feeling. The objective evidence was obtained in the specially designed
visual search task were achromatic and chromatic isoluminant stimuli were used in order to avoid so called pop-out
effect due to differences in light intensity. Each individual was instructed to define the symbols with aperture in the same
direction in four tasks. The color component differed in the visual search tasks according to the goals of study. The
results reveal that visual grouping is completed faster when visual stimuli have the same color and aperture direction.
The shortest reaction time is in the evening. What is more, the results of reaction time suggest that the analysis of two
grouping processes compete for selective attention in the visual system when similarity in color conflicts with similarity
in configuration of stimuli. The described effect increases significantly in the presence of mental fatigue. But it does not
have strong influence on the accuracy of task accomplishment.