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Goal-directed eye movements (saccades) bring peripheral objects of interest into high-acuity foveal vision. In preparation for the incoming foveal image, the perception of the saccade target may sharpen gradually before the eye movement is executed. Indeed, previous studies suggest that pre-saccadic attention shifts enhance sensitivity to high spatial frequencies (SFs) more than sensitivity to lower SFs. This pattern, however, was observed within a narrow frequency range and may reflect local changes in the shape of a broader underlying sensitivity profile. Depending on the development of the profile's shape, SFs above the previously examined range may profit less from saccade preparation. To assess the impact of saccade preparation on the shape of a broader sensitivity profile, we prompted observers to discriminate the orientation of a sinusoidal grating (the probe) presented briefly at the target of an impending saccade, at 10 dva (degree of visual angle) eccentricity. The probe's SF ranged from 1 to 5.5 cycles per dva (cpd) and was unpredictable on a given trial. We fitted observers' response accuracies across SFs with a log-parabolic, that is, inverted U-shaped function. Long before saccade onset, the profile peaked at .6 cpd and dropped off towards lower and higher SFs with broad bandwidth. During saccade preparation, the peak of the profile increased and shifted towards higher SFs while the bandwidth of the profile decreased. As a consequence of this reshaping process, pre-saccadic enhancement increased with SF up to 2.5 cpd, corroborating previous findings. Sensitivities to higher SFs, however, profited less from saccade preparation. We conclude that the extent of pre-saccadic enhancement to a particular SF is governed by its position on a broader sensitivity profile which reshapes substantially during saccade preparation. The shift of the profile's peak towards higher SFs increases resolution at the saccade target even when the features of relevant visual information are unpredictable.

In order to extract the relationship between head-eye movements and visual impressions while using Head-mounted displays (HMD) to view images, two types of response task experiments involving visual stimuli were conducted, using several visual angles. Both head movements and visual impressions increased with the visual angles during the observation of moving visual stimuli. Vestibulo-ocular reflex (VOR) gains as a ratio of eye and head movements decreased as the visual angle increased because the eye movement deviations were relatively small. When the viewer’s reaction required an action, such as rotating the head or aiming at a target, the strength of the viewer’s impression increased, though VOR gains remained at the same level.

While online experiments have shown tremendous potential to study larger and more diverse participant samples than is possible in the lab, the uncontrolled online environment has prohibited many types of psychophysical studies due to difficulties controlling the viewing distance and stimulus size. We introduce the Virtual Chinrest, a method that measures a participant’s viewing distance in the web browser by detecting a participant’s blind spot location. This makes it possible to automatically adjust stimulus configurations based on an individual’s viewing distance. We validated the Virtual Chinrest in two laboratory studies in which we varied the viewing distance and display size, showing that our method estimates participants’ viewing distance with an average error of 3.25 cm. We additionally show that by using the Virtual Chinrest we can reliably replicate measures of visual crowding, which depends on a precise calculation of visual angle, in an uncontrolled online environment. An online experiment with 1153 participants further replicated the findings of prior laboratory work, demonstrating how visual crowding increases with eccentricity and extending this finding by showing that young children, older adults and people with dyslexia all exhibit increased visual crowding, compared to adults without dyslexia. Our method provides a promising pathway to web-based psychophysical research requiring controlled stimulus geometry.

It is still unclear whether size constancy is an innate ability or whether it develops with age. As many developmental studies are limited to the child’s comprehension of the task instructions, here, an implicit measure of perceived size, namely, simple manual reaction time (RT), was opted for based on the assumption that perceptually bigger objects generate faster detection times. We examined size constancy in children (from 5 to 14 years of age) and adults using a simple RT approach. Participants were presented with pictures of tennis balls on a screen that was physically moved to two viewing distances. Visual stimuli were adjusted in physical size in order to subtend the same visual angle across distances, determining two conditions: a small-near tennis ball vs. a big-far tennis ball. Thanks to size constancy, the two tennis balls were perceived as different even though they were of equal size on the retina. Stimuli were also matched in terms of luminance. Participants were asked to react as fast as possible to the onset of the stimuli. The results show that the RTs reflected the perceived rather than the retinal size of the stimuli across the different age groups, such that participants responded faster to stimuli that were perceived as bigger than those perceived as smaller. Hence, these findings are consistent with the idea that size constancy is already present in early childhood, at least from the age of five, and does not require extensive visual learning.

In recent years, there have been many achievements in Mongolian studies. Scholars have carried out eye movement characteristics analysis and research from the aspects of reading gaze position effect, combined with the effect of high and low frequency words on gaze position and other aspects of Mongolian cognitive research. However, there is no systematic study on the influence of visual angle on Mongolian character recognition. This research addresses the above-mentioned problems, taking visual angle as the independent variable and reaction time as the dependent variable, selecting the commonly used Mongolian vowel consonants and divide them into seven visual angles of 2°, 4°, 7°, 10°, 13°, 16°, and 19°. Discussing the impact of the reaction time on the visual angle and the best recognition visual angle. The research showed that at 19°, the reaction time was the shortest and the recognition effect was better. Therefore, the best visual angle of Mongolian language could be identified in order to improve the efficiency of recognition, enrich the research in the field of Mongolian language study, and promote the development of Mongolian language research.

A patient suffering from visuo-spatial neglect was investigated as a special interest case during a study on the effectiveness of "restorative approaches" after visual field loss. This patient trained with our newly developed Virtual Reality (VR) system "Salzburg Visual Field Trainer" for 254 days. Perimetric results show a visual field expansion of 48.8% (left eye) and 36.8% (right eye) translating to an improvement of approximately 5.5° to 10.5° of visual angle. Further, subjective self-report shows improvements of up to 317% in visual field functionality. Our results indicate that patients suffering from visuo-spatial neglect could benefit from a VR-based restorative intervention.

Rationale: Among the serious consequences of alcohol use disorder (AUD) is the reduced ability to process visual information. It is also generally agreed that AUD tends to occur with disturbed excitation–inhibition (EI) balance in the central nervous system. Thus, a specific visual behavioral probe could directly qualify the EI dysfunction in patients with AUD. The tilt illusion (TI) is a paradigmatic example of contextual influences on perception of central target. The phenomenon shows a characteristic dependence on the angle between the inducing surround stimulus and the central target test. For small angles, there is a repulsion effect; for larger angles, there is a smaller attraction effect. The center-surround inhibition in tilt repulsion is considered to come from spatial orientational interactions between orientation-tuned neurons in the primary visual cortex (V1), and tilt attraction is from higher-level effects of orientation processing in the visual information processing.Objectives: The present study focuses on visual spatial information processing and explores whether chronic AUD patients in abstinence period exhibited abnormal TI compared with healthy controls.Methods: The participants are 30 male volunteers (20–46 years old) divided into two groups: the study group consists of 15 clinically diagnosed AUD patients undergoing abstinence from alcohol, and the control group consists of 15 healthy volunteers. The TI consists of a center target surround with an annulus (both target and annulus are sinusoidal grating with spatial frequency = 2 cycles per degree). The visual angle between center and surround is a variable restricted to 0°, ±15°, ±30°, or ±75°. For measuring the TI, participants have to report whether the center target grating orientation tilted clockwise or counterclockwise from the internal vertical orientation by pressing corresponding keys on the computer keyboard. No feedback is provided regarding response correctness.Results: The results reveal significantly weaker tilt repulsion effect under surround orientation ±15° (p < 0.05) and higher lapse rate (attention limitation index) under all tested surround orientations (all ps < 0.05) in patients with chronic AUD compared with health controls.Conclusions: These results provide psychophysical evidence that visual perception of center-contextual stimuli is different between AUD and healthy control groups.

Emotion processing has been a focus of research in psychology and neuroscience for some decades. While the evoked neural markers in human brain activations in response to different emotions have been reported, the temporal dynamics of emotion processing has received less attention. Differences in processing speeds, that depend on emotion type, have not been determined. Furthermore, behavioral studies have found that the right side of the human face expresses emotions more accurately than the left side. Therefore, accounting for both the content of the emotion and the visual angle of presentation from the perspective of the viewer, here we have investigated variability in the discrimination of happy and sad faces when the visual angle of presentation was Positive (right side of the face) compared to Negative (left side of the face). Furthermore, the temporal dynamics involved in processing happy and sad emotions have been compared. Regardless of visual angle, happy emotions were processed faster than sad emotions. However, the evoked response to sad emotions significantly increased in amplitude compared to that for happy emotions, when faces were presented at Positive visual angles only. Source reconstruction from sensor-level ERFs show localized activities in ventral and dorsal stream, including fusiform gyrus, lingual gyrus, putamen and Pre and Post central gyrus. Multivariate pattern analysis (MVPA) confirmed these findings – demonstrating successful decoding of happy and sad emotions only occurred when the facial expression was viewed from a positive visual angle, and that happy emotions were processed faster than sad emotions.

ObjectiveStudies on neuropsychological rehabilitation of visual field defects provide an inconsistent picture regarding the effectiveness of so-called “restorative approaches” in visual field recovery (VFR). During a current research project on the clinical evaluation of VFR - in combination with head mounted virtual reality displays (HMD) - a patient (“Patient 7”) suffering from visual neglect was investigated. Although the concept of VFR is originally not intended for patients suffering from higher cortical regions (as in neglect), we hypothesized that due to the strong attention-demanding training situation in HMDs, neglect patients might benefit from these intervention procedures based on restorative approaches.Methods and AnalysisPatient 7 was examined perimetrically using a “Humphrey Field Analyzer”, “Goldmann Perimetry” and our newly developed and validated eye-tracking supported perimetric methodology “Eye tracking based visual field analysis” (EFA). Based on these high resolution results from the EFA, the exact location of the transition area between intact and defect visual field of Patient 7 was assessed. Next, bright light stimuli were placed along this area in our newly developed HMD “Salzburg Visual Field Trainer” (SVFT). The aim was to stimulate neuroplasticity - according to the concept of restitutive approaches - in the corresponding cortical areas of the patient. Patient 7 trained with the SVFT for a time period of 254 days. In 6 appointments the objective and subjective rehabilitation progress was assessed.ResultsPerimetric assessment with the EFA shows an expansion of Patient 7’s visual field of 48.8% (left eye) and 36.8% (right eye) after 254 days of training with the SVFT. Individual areas in the patient’s visual field show a visual improvement of approximately 5.5° to 10.5° of visual angle. Subjective self-report of Patient 7 additionally shows improvements in self-evaluation of up to 317% in visual field functionality compared to self-evaluation on the first assessment date.ConclusionsThe results from Patient 7 indicate that patients suffering from visual neglect potentially benefit from a neuropsychological intervention with HMD based on the restorative concept of visual field recovery. However, further studies with large case numbers and a focus both on daily-life improvements and on a clear distinction between patients with lesions in earlier and higher cortical areas are needed to make empirically valid and generalizing statements about our findings.

Typical inherent properties of immersive Virtual Reality (VR) such as felt presence might have an impact on how well brand placements are remembered. In this study, we exposed participants to brand placements in four conditions of varying degrees of immersion and visual angle on the stimulus. Placements appeared either as poster or as puzzle. We measured the recall and recognition of these placements. Our study revealed that neither immersion nor the visual angle had a significant impact on memory for brand placements.

The aim of this study was to analyze the contrast sensitivity of spatial luminance and the color discrimination thresholds of the protan, deutan, and tritan axes of people with leprosy. This study included 8 subjects with leprosy (M = 4, W = 4, M = 33.38 ± 8.7) and 8 healthy subjects (M = 4, W = 4, M = 30.89 ± 5.8). The contrast sensitivity was evaluated by the Metropsis software version 11.0 with vertical sinusoidal grids of frequencies of 0.2, 0.5, 1, 5, 10, and 16 cycles per degree of visual angle (cpd) and color vision by the desaturated Lanthony D15 tests and the trivector and ellipse protocols of the Cambridge Color Test. The results showed significant differences between the groups in the processing of spatial frequencies of 0.2 (U = 14; p = .018); 5.0 (U = 45.0; p = .001); 10.0 (U = 45.0; p = .001), and 16.0 (U = 45.0; p = .001) cpd. The difference in color recognition through D15d (U = 4.0; p = .002). Ellipse 2 (U = 10.0; p = .012) and ellipse 3 (U = 9.0; p = .009) were discriminated against. Overall, the results indicate that leprosy changes the visual processing of low, medium, and high spatial frequencies, as well as the sensitivity of the short wavelength (tritan line of confusion) and long (protan line of confusion) cones.

We measured psychophysical thresholds for discriminating the speeds of two arrays of moving dots. The arrays could be juxtaposed or could be spatially separated by up to 10 degrees of visual angle, eccentricity being held constant. We found that the precision of the judgments varied little with separation. Moreover, the function relating threshold to separation was similar whether the arrays moved in the same, in opposite or in orthogonal directions. And there was no significant difference in threshold whether the two stimuli were initially presented to the same cerebral hemisphere or to opposite ones. How are human observers able to compare stimuli that fall at well separated positions in the visual field? We consider two classes of explanation: (i) Observers’ judgments might be based directly on the signals of dedicated ‘comparator neurons’, i.e. neurons drawing inputs of opposite sign from local regions of the visual field. (ii) Signals about local features might be transmitted to the site of comparison by a shared ‘cerebral bus’, where the same physical substrate carries different information from moment to moment. The minimal effects of proximity and direction (which might be expected to influence local detectors of relative motion), and the combinatorial explosion in the number of comparator neurons that would be required by (i), lead us to favor models of type (ii).

A wireless photovoltaic retinal prosthesis is currently being studied with the aim of providing prosthetic vision to patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD). The major challenge of a photovoltaic device is its limited power efficiency. Our retinal prosthetic design implements a unique divisional power supply scheme (DPSS) system that provides the electrical power generated by all of the solar cells to only a subset of electrodes at any moment in time. The aim of the present study was to systematically characterize the spatiotemporal integration performance of the system under various DPSS conditions using human subjects and a psychophysical approach. A 16x16 pixels LED array controlled by Arduino was used to simulate the output signal of the DPSS design, and human performance under different visual stimulations at various update frequencies was then used to assess the spatiotemporal capability of retinal prostheses. The results showed that the contrast polarity of the image, image brightness, and division number influenced the lower limit of the update frequency of the DPSS system, while, on the other hand, visual angle, ambient light level, and stimulation order did not affect performance significantly. Pattern recognition by visual persistence with spatiotemporal integration of multiple frames of sparse dots is a feasible approach in retinal prosthesis design. These findings provide an insight into how to optimize a photovoltaic retinal prosthesis using a DPSS design with an appropriate update frequency for reliable pattern recognition. This will help the development of a wireless device able to restore vision to RP and AMD patients in the future.

A single experiment required 40 younger and older adults to discriminate global shape as depicted by Glass patterns (concentric and radial organizations). Such patterns have been widely used for decades, because in order to successfully perceive the depicted shape, the visual system has to detect both locally oriented features (dipoles) and their alignments across extended regions of space. In the current study, we manipulated the number of constituent dipoles in the stimulus patterns (40 or 200), the noise-to-signal ratio (zero, 1.0, & 5.0), and the pattern size (6.0 & 25.0 degrees visual angle). The observers’ shape discrimination accuracies (d’ values) decreased markedly as the amount of noise increased, and there were smaller (but significant) effects of both overall pattern size and the number of stimulus dipoles. Interestingly, while there was a significant effect of age, it was relatively small: the overall d’ values for older and younger adults were 2.07 and 2.34, respectively. Older adults therefore retain an effective ability to visually perceive global shape, even for sparsely-defined patterns embedded in noise.

Pupillary responses and associated vergence eye movements were monitored during imagery of objects of differing sizes ("large" or "small") from varying distances ("near" or "far"). Objects' imagined size and distance affected oculomotor behavior. Objects visualized as "far" resulted in the larger pupil dilations and smaller visual angle, while small objects imagined "near" were associated with smaller pupils in contrast to relatively larger pupils when imagined as "far" away. Furthermore, near objects resulted in larger visual angle, and particularly, vergence adjustments were observed that were dependent on imagined size and distance of the small objects. The findings are consistent with the idea that imagery emulates perception, also at the embodied level of oculomotor behaviors.

Egocentric distance estimation has been shown to depend on wearing safety gear, which promotes compensatory behavior, and on target type, which regulates fight-or-flight responses. We hypothesized that the two factors interact, possibly in asymmetric fashion, and set out to uncover the limits of this interaction in a perceptual task where individuals wearing helmets or baseball caps estimated egocentric distance to non-threatening and threatening animals depicted on cards (i.e., safe and unsafe targets). We found that, compared to participants wearing caps, participants wearing helmets overshoot distance estimations and were able to distinguish not only between targets situated at two depth levels as participants wearing caps could, but also between safe targets situated at wide and narrow visual angles. Our findings help define the interaction between safety devices and target type, thereby contributing to the debate between advocates of prevention models and those who maintain that these are offset by compensatory strategies.

The basis for how we represent temporal intervals in memory remains unclear. One proposal, the mental time line theory (MTL), posits that our representation of temporal duration depends on a horizontal mental time line, thus suggesting that the representation of time has an underlying spatial component. Recent work suggests that the MTL is a learned strategy, prompting new questions of when and why MTL is used to represent temporal duration, and whether time is always represented spatially. The current study examines the hypothesis that the MTL may be a time processing strategy specific to centrally-located stimuli. In two experiments (visual eccentricity and prismatic adaptation procedures), we investigated the magnitude of the rightward bias, an index of the MTL, in central and peripheral space. When participants performed a supra-second temporal interval reproduction task, we observed a rightward bias only in central vision (within 3° visual angle), but not in the peripheral space (approximately 6–8° visual angle). Instead, in the periphery, we observed a leftward bias. The results suggest that the MTL may be a learned strategy specific to central space and that strategies for temporal interval estimation that do not depend on MTL may exist for stimuli perceived peripherally.

Electrically stimulating early visual cortex results in a visual percept known as a phosphene. Although phosphenes can be evoked by a wide range of electrode sizes and current amplitudes, they are invariably described as small. To better understand this observation, we electrically stimulated 93 electrodes implanted in the visual cortex of 13 human subjects who reported phosphene size while stimulation current was varied. Phosphene size increased as the stimulation current was initially raised above threshold, but then rapidly reached saturation. Phosphene size also depended on the location of the stimulated site, with size increasing with distance from the foveal representation. We developed a model relating phosphene size to the amount of activated cortex and its location within the retinotopic map. First, a sigmoidal curve was used to predict the amount of activated cortex at a given current. Second, the amount of active cortex was converted to degrees of visual angle by multiplying by the inverse cortical magnification factor for that retinotopic location. This simple model accurately predicted phosphene size for a broad range of stimulation currents and cortical locations. The unexpected saturation in phosphene sizes suggests that the functional architecture of cerebral cortex may impose fundamental restrictions on the spread of artificially evoked activity and this may be an important consideration in the design of cortical prosthetic devices.SIGNIFICANCE STATEMENT Understanding the neural basis for phosphenes, the visual percepts created by electrical stimulation of visual cortex, is fundamental to the development of a visual cortical prosthetic. Our experiments in human subjects implanted with electrodes over visual cortex show that it is the activity of a large population of cells spread out across several millimeters of tissue that supports the perception of a phosphene. In addition, we describe an important feature of the production of phosphenes by electrical stimulation: phosphene size saturates at a relatively low current level. This finding implies that, with current methods, visual prosthetics will have a limited dynamic range available to control the production of spatial forms and that more advanced stimulation methods may be required.

Although the feasibility of brain-computer interface (BCI) systems based on steady-state visual evoked potential (SSVEP) has been extensively investigated, only a few studies have evaluated its clinical feasibility in patients with locked-in syndrome (LIS), who are the main targets of BCI technology. The main objective of this case report was to share our experiences of SSVEP-based BCI experiments involving five patients with LIS, thereby providing researchers with useful information that can potentially help them to design BCI experiments for patients with LIS. In our experiments, a four-class online SSVEP-based BCI system was implemented and applied to four of five patients repeatedly on multiple days to investigate its test-retest reliability. In the last experiments with two of the four patients, the practical usability of our BCI system was tested using a questionnaire survey. All five patients showed clear and distinct SSVEP responses at all four fundamental stimulation frequencies (6, 6.66, 7.5, 10 Hz), and responses at harmonic frequencies were also observed in three patients. Mean classification accuracy was 76.99% (chance level = 25%). The test-retest reliability experiments demonstrated stable performance of our BCI system over different days even when the initial experimental settings (e.g., electrode configuration, fixation time, visual angle) used in the first experiment were used without significant modifications. Our results suggest that SSVEP-based BCI paradigms might be successfully used to implement clinically feasible BCI systems for severely paralyzed patients.

PURPOSE: It is more difficult to perceive the direction of motion of larger, high contrast patterns than smaller, low contrast patterns due to spatial suppression. Spatial suppression of motion is considered important to the segmentation of moving objects in the visual environment. Previous studies have shown that such spatial suppression of motion is reduced in older adults in central vision, to the extent that older adults can have better sensitivity than younger adults for foveally presented stimuli. Our study was designed to explore whether spatial suppression of motion is similarly reduced for older adults in parafoveal regions and whether divided attention impacts on suppression strength because attention is known to impact on spatial interactions. METHODS: Twenty younger (19-34 years) and 18 older (61-77 years) adults completed a single task, where observers identified the direction of a drifting Gabor patch of variable size (σ of the Gaussian envelope = 0.5, 1, 2, 3, 4°) presented at 10 degrees of visual angle while observing a central fixation marker, and a dual task, where observers were required to divide their attention across two stimuli, the peripheral drifting Gabor patch and a central rapid serial visual presentation (RSVP) stream. RESULTS: Older adults showed increased spatial suppression of motion relative to younger adults for both tasks (main effect of group: p

Abstract Background Edge plays a special role in spatial perception and as well as in determining the brightness of a surface within borders. The aim of our study was to measure threshold brightness in different levels of edges thickness. Methods Steven’s power law for circles modulating in luminance was estimated for 30 subjects (mean age 24 years, SD 3.3, 13 female). Stimuli were presented on the iMac display using the 11-bit graphic board and consisted of two circles of 3° of visual angle, separated by 10°. We tested 7 levels of Michelson contrast: 7, 8, 10, 15, 26, 50, and 100. Three edges filtering were tested (0.3, 0.8, and 1.5° of smoothing). The subjects’ task was to judge the brightness of the edge filtered circle compared with the circle of the hard edge which was considered the modulus and received an arbitrary level of 50, representing the amount of brightness perception. In each trial, the same contrast level was presented in both circles. Five judgments were performed for each contrast level in edge filtering. Results We found an increase in the power law exponent as the increase of the edge filtering (for sigma of 0.3 = 0.43, sigma of 0.8 = 0.73, and sigma 1.5 = 0.97). All power function fitting had high correlation coefficients (r2 = .94, r2 = .95, r2 = .97, respectively to sigma 0.3, 0.8, and 1.5) passing to the model’s adhesion criteria. Conclusions There was a progressive distortion on the figure brightness perception as increasing the edge filtering suggesting the control of edges on the polarity of the overall brightness. Also, perceived brightness was increasingly veridical with increased filtering, approaching 1:1 correspondence at 1.5 sigmas.

About 30-40% of stroke patients suffer from visual field defects following injury. These can interfere with the standard neuropsychological assessment and complicate the interpretation of tests that use visual materials. However, information about the integrity of a patient's central visual field is often unavailable. We, therefore, designed a screening tool, the computerized visual field test (c-VFT), specifically targeted at providing easily available, but rough, information about patients' central visual field. c-VFT was tested in two samples of stroke patients. Eleven patients were tested on c-VFT and on the Esterman test. Five patients were tested on c-VFT and the Humphrey Visual Field Analyzer (HFA), central 10-2. Criterion validity of the c-VFT was investigated by calculating quadrantwise intraclass correlation for both comparisons. For the HFA comparison, we also calculated point-to-point intraclass correlation, sensitivity, and specificity. Analyses revealed moderately good correspondence between c-VFT and the Esterman test, and between c-VFT and HFA 10-2, respectively. When looking specifically at test points within one degree of visual angle apart in the two tests, intraclass correlation increased. For these points, the sensitivity of c-VFT was 0.89 and specificity was 0.97. While the c-VFT is not designed to be diagnostic nor to replace the detailed visual field analysis, this study shows that it provides a reasonable screening of the central visual field. The test can easily be used and will be made freely available to neuropsychological clinicians and researchers.The open access test can be found here: https://tinyurl.com/ysz9b28c

Background: The ability to read is an important factor in the quality of life. Choroideremia is an inherited retinal degeneration presenting with gradual, progressive constriction of the central visual field, providing a useful disease model to investigate the impact of the visual field on reading ability.Objective: The aim of this study was to provide practical guidance on the usefulness of measuring reading ability in patients.Method: The Radner Reading Test was administered to 33 patients (65 eyes with choroideremia). To quantify the residual retinal area, the patients underwent microperimetry and imaging. The visual angle subtended by the largest letter read by each subject was calculated using Emsley’s Model Eye.Results: A minimum of 1 letter must be seen to allow the eye to read, with preservation of foveal sensitivity. The relationship between reading speed and acuity varies with the visual field. The reading speed is higher in eyes with an intact fovea (p < 0.001 right eye, p = 0.06 left eye). Qualitative analysis of the direction of the intact retina did not indicate any directional impact on measurements.Conclusions: In order to read, an eye must have enough retinal width close to the fovea to see at least 1 full letter. Direction of print does not impact the ability to read, allowing results from different languages to be combined in clinical trials.

The capacity to perceive color in the peripheral field has attracted research interest for more than a decade. There is evidence that sensitivity to red-green color variations is lower than for yellow-blue in peripheral vision. Whether, and to what extent, color vision affects the visual focus of attention, which is normally much smaller than the visual field, has not yet been examined. We used a sport-specific decision-making task to assess whether the color of the jersey worn by players appearing in the periphery influences decision making by affecting the attentional and perceptual capabilities. Pairs of players wearing chromatic (blue, yellow, red, and green) and achromatic (black, white) colored jerseys were briefly presented across a range of visual angles on a 6 m concave immersive screen. Participants were required to decide to whom to pass and recall relevant information. Findings indicate that color perception changes vary with increasing visual angle, but that the focus of attention is too small to be influenced by jersey color sensitivity. Decision-making performance decreases with increasing visual angle, but is not influenced by color. The implications for decision-making processes in sport and other professional domains are discussed.

Eye gaze of is an informative social signal in interactions with other humans and also with virtual agents (VA). But for a successful communication, users have to accurately perceive the VA's point of gaze (POG). In our study, participants sitting opposite to a VA at a table indicated its POG by positioning a token on the table surface. We measured the perceptual accuracy within and between participants as well as the participants' response times and eye movements for five horizontally aligned gaze targets. We demonstrated that perceiving the VA met perceptual benchmarks from human lookers: a) variances within and between participants were only slightly larger, b) the VA's visual angle was linearly overestimated, and c) variances increased with the visual angle. Finally, participants showed large individual differences but were consistent in their own gaze behaviour and response times across trials and gaze targets.

Purpose The dorsal attention network (DAN) and the ventral attention network (VAN) are known to support visual attention, but the influences of ocular dominance on the attention networks are unclear. We aimed to explore how visual cortical asymmetry of the attention networks correlate with neurophysiological oscillation and connectivity markers of attentional processes. Methods An oddball task with concentric circle stimuli of three different sizes (i.e., spot size of 5°, 20°, or 30° of visual angle) was used to vary task difficulty. Event-related oscillations and interareal communication were tested with an electroencephalogram-based visual evoked components as a function of ocular dominance in 30 healthy subjects. Results Accuracy rates were higher in the dominant eyes compared with the nondominant eyes. Compared with the nondominant eyes, the dominant eyes had higher theta, low-alpha, and low-beta powers and lower high-alpha powers within the nodes of VAN and DAN. Furthermore, visual information processed by the dominant and nondominant eye had different fates, that is, the dominant eyes mainly relied on theta and low-alpha connectivity within both the VAN and the DAN, whereas the nondominant eyes mainly relied on theta connectivity within the VAN and high-alpha connectivity within the DAN. The difference in accuracy rate between the two eyes was correlated with the low-alpha oscillations in the anterior DAN area and low-alpha connectivity of the left DAN. Conclusions The ocular dominance processing and interareal communication reveal a cortical asymmetry underlying attention, and this reflects a two-way modulatory mechanism within attention networks in the human brain.

A number of virtual reality head-mounted displays (HMDs) with integrated eye trackers have recently become commercially available. If their eye tracking latency is low and reliable enough for gaze-contingent rendering, this may open up many interesting opportunities for researchers. We measured eye tracking latencies for the Fove-0, the Varjo VR-1, and the High Tech Computer Corporation (HTC) Vive Pro Eye using simultaneous electrooculography measurements. We determined the time from the occurrence of an eye position change to its availability as a data sample from the eye tracker (delay) and the time from an eye position change to the earliest possible change of the display content (latency). For each test and each device, participants performed 60 saccades between two targets 20° of visual angle apart. The targets were continuously visible in the HMD, and the saccades were instructed by an auditory cue. Data collection and eye tracking calibration were done using the recommended scripts for each device in Unity3D. The Vive Pro Eye was recorded twice, once using the SteamVR SDK and once using the Tobii XR SDK. Our results show clear differences between the HMDs. Delays ranged from 15 ms to 52 ms, and the latencies ranged from 45 ms to 81 ms. The Fove-0 appears to be the fastest device and best suited for gaze-contingent rendering.

Songbirds possess acute vision. How higher brain centers represent basic and parameterized visual stimuli to process sensory signals according to their behavioral importance has not been studied in a systematic way. We therefore examined how carrion crows (Corvus corone) and their nidopallial visual neurons process global visual motion information in dynamic random-dot displays during a delayed match-to-sample (DMS) task. The behavioral data show that moderately fast motion speeds (16 degrees of visual angle/second) result in superior direction discrimination performance. To characterize how neurons encode and maintain task-relevant visual motion information, we recorded the single-unit activity in the telencephalic association area ‘nidopallium caudolaterale’ (NCL) of behaving crows. The NCL is considered to be the avian analog of the mammalian prefrontal cortex. Almost a third (28%) of randomly-selected NCL neurons responded selectively to the motion direction of the sample stimulus, mostly to downward motions. Only few NCL neurons (7.5%) responded consistently to specific motion directions during the delay period. In error trials, when the crows chose the wrong motion direction, the encoding of motion direction was significantly reduced. This indicates that sensory representations of NCL neurons are relevant to the birds’ behavior. These data suggest that the corvid NCL, even though operating at the apex of the telencephalic processing hierarchy, constitutes a telencephalic site for global motion integration. This article is protected by copyright. All rights reserved.

Visual discomfort is predicted from a luminance map with a model based on the receptive field mechanism in the human eye. A centre-surround receptive field is described by a Difference of Gaussians. Eight commercially available office luminaires are assessed for visual discomfort in a paired comparison experiment. The correlation between the subjective data and the receptive field model is optimized for three factors: the centre Gaussian width, the surround Gaussian width and the centre-to-surround weighing factor (WF). A centre and surround visual angle of 0.53 and 2.19 min arc, respectively, and a WF of 0.87 result in a coefficient of determination of 0.77. The model is validated independently with magnitude estimation data obtaining a coefficient of determination of 0.82. Where the standard unified glare rating method fails (coefficient of determination of 0.45), the receptive field model ameliorates predictability for visual discomfort. The model based on receptive fields is promising to replace current standard glare metrics, specifically when non-uniform luminaires are to be evaluated.

Video-based eye tracking relies on locating pupil center to measure gaze positions. Although widely used, the technique is known to generate spurious gaze position shifts up to several degrees in visual angle because pupil centration can change without eye movement during pupil constriction or dilation. Since pupil size can fluctuate markedly from moment to moment, reflecting arousal state and cognitive processing during human behavioral and neuroimaging experiments, the pupil size artifact is prevalent and thus weakens the quality of the video-based eye tracking measurements reliant on small fixational eye movements. Moreover, the artifact may lead to erroneous conclusions if the spurious signal is taken as an actual eye movement. Here, we measured pupil size and gaze position from 23 human observers performing a fixation task and examined the relationship between these two measures. Results disclosed that the pupils contracted as fixation was prolonged, at both small (

The kappa effect is a spatiotemporal illusion where duration is overestimated with the increase of space. This effect is typically demonstrated with three successive stimuli marking two neighboring empty time intervals, and the classical imputed velocity model, in principle, does not help to predict any spatial effects when only two stimuli, marking single intervals, are presented on each trial. We thus conducted three experiments, examining requirements for the occurrence of the kappa effect with only two visual stimuli. An interstimulus interval between the two stimuli was 217 (short) or 283 ms (long), and participants categorized the presented interval as ‘short’ or ‘long’. The key finding is that participants tended to respond ‘short’ more frequently than ‘long’ when both stimuli were delivered from the same location, whereas the relative frequency of ‘long’ responses was increased when the two stimuli were delivered from different locations in most directions (i.e., horizontally, vertically, diagonally; Experiment 1). This kappa effect clearly occurred when each stimulus was located 8° apart from the fovea in visual angle, but it was reduced when each stimulus was further deviated from the fovea, regardless of whether the two stimuli were presented in the vertical or the horizontal direction (Experiments 2 and 3). Moreover, increasing the spatial distance between the two stimuli from 15 to 30 cm magnified the effect only in a limited condition (Experiment 3). Implications of these results were discussed in terms of the Bayesian model predicting the effects of spatial acuity.

Objective The Navon effect (Navon, 1977) is an automatic tendency to process the global picture prior to local details when processing compound patterns. However, several recent studies have reported that this effect is lacking in attention-deficit/hyperactivity disorder (ADHD). Although previous research has shown that the Navon effect is strongly affected by visual angles, whether this phenomenon will also be observed in ADHD is yet to be understood. We examine the lack of the Navon effect in ADHD under various visual angles to ensure that this phenomenon is not an artifact of saliency. Method By employing three different visual angles for the local stimuli, global and local processing of Navon-type hierarchical letters was examined in participants with ADHD (n = 15) and a comparison group (n = 17). Results ADHD participants presented with a lack of the Navon effect without local processing deficit regardless of visual angle, in comparison to non-ADHD participants. Conclusion A lack of global precedence and global-to-local interference without local processing deficit can be generalized in ADHD. This suggests that people with ADHD experience difficulties in processing the "whole picture," and it also challenges the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; American Psychiatric Association, 2013) criteria of ADHD in which the failure to pay close attention to details was emphasized. Moreover, the current results have important implications for understanding ADHD and could also have significant clinical value.

What we see influences our emotions. Technology often mediates the visual content we perceive. Visual angle is an essential parameter of how we see such content. It operationalizes visible properties of human–computer interfaces. However, we know little about the content-independent effect of visual angle on emotional responses to audiovisual stimuli. We show that visual angle alone affects emotional responses to audiovisual features, independent of object perception. We conducted a 2 × 2 × 3 factorial repeated-measures experiment with 143 undergraduate students. We simultaneously presented monochrome rectangles with pure tones and assessed valence, arousal, and dominance. In the high visual angle condition, arousal increased, valence and dominance decreased, and lightness modulated arousal. In the low visual angle condition, pitch modulated arousal, and lightness affected valence. Visual angle weights the affective relevance of perception modalities independent of spatial representations. Visual angle serves as an early-stage perceptual feature for organizing emotional responses. Control of this presentation layer allows for provoking or avoiding emotional response where intended.

The Moon often appears larger near the perceptual horizon and smaller high in the sky though the visual angle subtended is invariant. We show how this illusion results from the optimization of a projective geometrical frame for conscious perception through free energy minimization, as articulated in the Projective Consciousness Model. The model accounts for all documented modulations of the illusion without anomalies (e.g., the size-distance paradox), surpasses other theories in explanatory power, makes sense of inter- and intra-subjective variability vis-a-vis the illusion, and yields new quantitative and qualitative predictions., Main 10 pages, 3 figures, Supplement 19 pages

The spontaneity and ease with which we point understates the gesture’s significance to understanding cognition. Onset of pointing in infancy predicts early word acquisition and signals a capacity for shared intentionality. Yet, notwithstanding its importance, there is little research on the perception of pointing and its referents. Here we show that perceptual acuity for discerning where another person is pointing is remarkably accurate. Thresholds, as low as 0.5° of visual angle across an interpersonal distance of ∼2 m, are modulated by the referent’s location in space and the hand used to point and remain constant when the pointer’s eyes are occluded from view and when ‘embodiment’ cues are enhanced or minimized. Pointing with the index finger not only directs attention toward a general region of space but the morphology of arm, hand and finger can be used to discern the location of the pointer’s attention with precision.

The influence of visual experience on spatial imagery is still not fully understood. Although numerous experiments have been interpreted as showing considerable limitations in the functioning of imagery processes in people who are totally blind, especially those who were born blind or had early onset of blindness, there are studies suggesting that no significant differences in this area can be detected between blindfolded sighted and nonsighted individuals. There are claims that in some cases persons deprived of visual experience perform better than blindfolded sighted individuals (for a review, see Cattaneo et al., 2008). The differences in the results of the experiments reported in this and in other sources seem to follow from the specificity of the imagery task rather than from the imagery operation (mental imagery activity) being tested (see, for example, Cornoldi & Vecchi, 2003). Testing imagery scaling operations may serve as an example. Mental scaling transformation is an operation that involves changing the size of an image found, for example, when sighted persons compare objects (Larsen & Bundesen, 1978). The reaction time increased with the size ratio of objects (see also Bennett & Warren, 2002; Craddock & Lawson, 2009). Some research suggests that adults without prior visual experience do not understand that the size of an object imagined to be moving away must be reduced in accordance with the principle of perspective (Arditi, Holtzman, & Kosslyn, 1988; Vanlierde & Wanet-Defalque, 2005). There is, however, research providing evidence that it is unlikely that these difficulties result from an inability to perform the operation of mental scaling (Kennedy, 1993; Wnuczko & Kennedy, 2014). For clarity of argumentation, it is important to distinguish between linear size (which can, for example, be measured in centimeters), and angular size. The linear size of a particular object is an objective property that does not change over time. The ability to evaluate the linear size can therefore be treated as an indication of conceptual knowledge related to typical sizes of objects encountered in the real world. These sizes may change only in fantasy (for example, in Alice in Wonderland). In visual perception, the angular size--that is, the angle at which the observed object subtends at the eye--changes with the distance between the object and the observer. Angular size is usually measured in degrees of the arc, although in some research it was shown by pointing to the ends of the imagined object. In those cases the pointing span indicated the angular size (see, for example, Arditi et al., 1988). In visual perception, identical objects placed at different distances from the observer create images on the retina that differ in size. It is also possible to determine the changing pointing span for these objects. The size differences are reflected in verbal descriptions: a lake observed from an airplane may be compared to a puddle, and a dog observed from a distance may seem as small as an ant. We get this impression despite being aware that the linear size of these objects does not change (this is the mechanism of size constancy). Visual angular size has its analogy in imagery. Kosslyn (1978) defines angular size as the visual angle of the mind's eye, and provides empirical evidence that sighted persons imagine objects as being a certain distance away from the mind's eye. Sighted persons first experience size constancy in infancy (Slater, Mattock, & Brown, 1990). This constancy, functioning as automatic inference, makes it possible to assess the linear size of an object on the basis of its optical size and the distance. The accuracy of the inference involved in the process of visual perception improves gradually, and at early school age is not yet fully developed (Granrud & Schmechel, 2006). Developmental progress in understanding the relationship between angular and linear size can be observed in drawings made by sighted children. …

Theories of lightness, like theories of perception in general, can be categorized as high-level, low-level, and mid-level. However, I will argue that in practice there are only two categories: one-stage mid-level theories, and two-stage low-high theories. Low-level theories usually include a high-level component and high-level theories include a low-level component, the distinction being mainly one of emphasis. Two-stage theories are the modern incarnation of the persistent sensation/perception dichotomy according to which an early experience of raw sensations, faithful to the proximal stimulus, is followed by a process of cognitive interpretation, typically based on past experience. Like phlogiston or the ether, raw sensations seem like they must exist, but there is no clear evidence for them. Proximal stimulus matches are postperceptual, not read off an early sensory stage. Visual angle matches are achieved by a cognitive process of flattening the visual world. Likewise, brightness (luminance) matches depend on a cognitive process of flattening the illumination. Brightness is not the input to lightness; brightness is slower than lightness. Evidence for an early (< 200 ms) mosaic stage is shaky. As for cognitive influences on perception, the many claims tend to fall apart upon close inspection of the evidence. Much of the evidence for the current revival of the ‘new look’ is probably better explained by (1) a natural desire of (some) subjects to please the experimenter, and (2) the ease of intuiting an experimental hypothesis. High-level theories of lightness are overkill. The visual system does not need to know the amount of illumination, merely which surfaces share the same illumination. This leaves mid-level theories derived from the gestalt school. Here the debate seems to revolve around layer models and framework models. Layer models fit our visual experience of a pattern of illumination projected onto a pattern of reflectance, while framework models provide a better account of illusions and failures of constancy. Evidence for and against these approaches is reviewed.

The cancellation task is a visual search task requiring rapid and accurate placement of a mark through each occurrence of a specific target displayed in an array of distractors on a sheet of paper. This study of 30 university students was conducted to examine the effects of visual field constriction on visual search in the cancellation task. Participants administered the orderly array cancellation task and the random array cancellation task while their visual fields were unrestricted (full vision), or restricted to 5°, 10°, or 15° by tunnel vision simulation goggles. The number of errors, time to completion, and the performance score as an index of cancelling efficiency were calculated. Results showed that the time to completion and the performance score were significantly greater in the random array cancellation task than in the structured array cancellation task, and in the narrowest visual field condition (5°) than in other visual field conditions (10°, 15°, and full vision). These results suggest that the visual search efficiency was degraded when the visual field was restricted to be less than 5° in the orderly and random array cancellation tasks used for this study.

Infants show facility for discriminating between individual faces within hours of birth. Over the first year of life, infants' face discrimination shows continued improvement with familiar face types, such as own-race faces, but not with unfamiliar face types, like other-race faces. The goal of this meta-analytic review is to provide an effect size for infants' face discrimination ability overall, with own-race faces, and with other-race faces within the first year of life, how this differs with age, and how it is influenced by task methodology. Inclusion criteria were (a) infant participants aged 0 to 12 months, (b) completing a human own- or other-race face discrimination task, (c) with discrimination being determined by infant looking. Our analysis included 30 works (165 samples, 1,926 participants participated in 2,623 tasks). The effect size for infants' face discrimination was small, 6.53% greater than chance (i.e., equal looking to the novel and familiar). There was a significant difference in discrimination by race, overall (own-race, 8.18%; other-race, 3.18%) and between ages (own-race: 0- to 4.5-month-olds, 7.32%; 5- to 7.5-month-olds, 9.17%; and 8- to 12-month-olds, 7.68%; other-race: 0- to 4.5-month-olds, 6.12%; 5- to 7.5-month-olds, 3.70%; and 8- to 12-month-olds, 2.79%). Multilevel linear (mixed-effects) models were used to predict face discrimination; infants' capacity to discriminate faces is sensitive to face characteristics including race, gender, and emotion as well as the methods used, including task timing, coding method, and visual angle. (PsycINFO Database Record

Spatial frequency refers to the number of cycles per degree of visual angle in a pattern. When low spatial frequency gratings are moving quickly, we see flicker at lower contrasts than we see pattern but we experience the reverse at high spatial frequencies. The possibility of a visual deficit in dyslexics has recently been investigated within the theoretical framework of spatial frequency analysis. Visible persistence is one measure of temporal processing in spatial frequency channels and refers to the continued perception of a stimulus after it has been physically removed. Lovegrove and colleagues attempted to predict from Breitmeyer's theory the effect that different types of spatial context may have on reading accuracy in dyslexics and controls. The results with different modes of visual presentation and with the effects of wavelength on reading in dyslexics and controls will be further investigated in our laboratory and are encouraging.

The issue of information pollutions have become more and more serious these days among which the ones produced by academic cheating has the most catastrophic consequence. Academic cheating is rooted in abandon of integrity; the pursuit of individual interests over academic value, and fabrication of fake innovation with repeat or made up facts

Perceptual organization refers to constraints on what is perceived (e.g., with visual angle held constant, apparent size and apparent distance covary; apparent figural quality varies with apparent simplicity of configuration). Three major classes of organizational phenomena (space, shape/form, and movement) have been important to perceptual theory. Theories of organization differ in the roles assigned to stimulus structure (intrastimulus constraints) and to mental structure (interresponse constraints) and on the degree of wholism posited (i.e., the size of the structure within which constraints are strong). The major perceptual theories are analyzed in these terms. Phenomena are reviewed that very sharply limit the tenability of any theory to which spatial or temporal wholism is important and that clearly demonstrate mental structure in the absence of stimulus structure. The class of theory proposed by J. S. Mill and Helmholtz—that we perceive by fitting the most likely or expected (global) object or event to the sampled (local) sensory components—remains the one best suited to the widest range of organizational phenomena (including the Gestalt phenomena). Mental structure does not simply reflect physical (stimulus) structure, however, and the different levels of organization must be separated before such theories can be seriously considered and developed.

Patients with central vision loss obtain visual information by fixating on an object eccentrically with a preferred retinal locus of fixation (PRL). Patients do not always choose the most efficient PRL position, and as a consequence, visual performance is not always fully exploited. This study investigates whether PRLs can be induced by applying systematic stimulus relocations. The PRL was trained using a central scotoma simulation in 15 healthy subjects. They performed different visual tasks during four sessions, after which their reading performance was evaluated. In five subjects the stimulus was relocated to the left hemifield whenever a saccade would place the stimulus on the opposite hemifield. In five different subjects the relocation was inversed: The stimulus was located in the right hemifield. The relocation was 7.5° of visual angle and it was applied horizontally. Five additional subjects naturally chose the PRL location. They were used as the control group to evaluate the development of a PRL. After training, subjects performed visual search tasks on static stimuli. Evaluation after training showed that systematic stimulus relocations can be used to influence the development of the PRL. These results might be significant for the development of training strategies for the visually impaired.

Adaptation to the duration of a visual stimulus causes the perceived duration of a subsequently presented stimulus with a slightly different duration to be skewed away from the adapted duration. This pattern of repulsion following adaptation is similar to that observed for other visual properties, such as orientation, and is considered evidence for the involvement of duration-selective mechanisms in duration encoding. Here, we investigated whether the encoding of duration - by duration-selective mechanisms - occurs early on in the visual processing hierarchy. To this end, we investigated the spatial specificity of the duration after-effect in two experiments. We measured the duration after-effect at adapter-test distances ranging between 0 and 15° of visual angle and for within- and between- hemifield presentations. We replicated the duration after-effect: the test stimulus was perceived to have a longer duration following adaptation to a shorter duration, and a shorter duration following adaptation to a longer duration. Importantly, this duration after-effect occurred at all measured distances, with no evidence for a decrease in the magnitude of the after-effect at larger distances or across hemifields. This shows that adaptation to duration does not result from adaptation occurring early on in the visual processing hierarchy. Instead, it seems likely that duration information is a high-level stimulus property that is encoded later on in the visual processing hierarchy.

The Mona Lisa effect describes the phenomenon when the eyes of a portrait appear to look at the observer regardless of the observer's position. Recently, the metaphor of a cone of gaze has been proposed to describe the range of gaze directions within which a person feels looked at. The width of the gaze cone is about five degrees of visual angle to either side of a given gaze direction. We used functional magnetic resonance imaging to investigate how the brain regions involved in gaze direction discrimination would differ between centered and decentered presentation positions of a portrait exhibiting eye contact. Subjects observed a given portrait's eyes. By presenting portraits with varying gaze directions-eye contact (0°), gaze at the edge of the gaze cone (5°), and clearly averted gaze (10°), we revealed that brain response to gaze at the edge of the gaze cone was similar to that produced by eye contact and different from that produced by averted gaze. Right fusiform gyrus and right superior temporal sulcus showed stronger activation when the gaze was averted as compared to eye contact. Gaze sensitive areas, however, were not affected by the portrait's presentation location. In sum, although the brain clearly distinguishes averted from centered gaze, a substantial change of vantage point does not alter neural activity, thus providing a possible explanation why the feeling of eye contact is upheld even in decentered stimulus positions.

The aim of our study was to investigate whether different circle sizes, in conditions of pure size judgment and in a simple contextual judgment with an interfering depth suggesting background, produce different size perceptions. We used the magnitude estimation to obtain the apparent size of circles under two different experimental conditions: with a neutral black background and with a convergent gradient to generate an artificial horizon to evoke depth cues. Twenty-two subjects with normal or corrected-to-normal visual acuity (mean age = 21.3 yrs; SD = 1.6) were tested. The procedure consisted of two gray circles at luminance of 40 cd/m2, separated 10 degrees of visual angle apart from each other. On the left side was always present the reference circle (visual angle of 1.1 degree) in which was assigned an arbitrary value of 50 was assigned. The subjects' task was to judge the size of the circles appearing in the right side of the monitor screen assigning a number proportional to the perceived altered size, relative to the reference circle. Seven different sizes (0.6, 0.8, 1.0, 1.1, 1.3, 1.4, 1.5 degrees) were presented in each condition. Our results have shown a high correlation for circle size and depth conditions (R = 0.987 and R = 0.997) between the logs of the stimuli and the subjective magnitude estimated values. The exponents obtained by the Power Law were 0.79 and 1.09, respectively to each condition. Additionally, a gender effect was observed in which males had showed an expansive perception of size with no dependence on the background. We concluded that in the induced depth condition, the perception of the circle sizes were judged subjectively closer to their respective physical size than in the condition of free visual cues. Our data reinforces the integrative manner of perceptual system when working with the sensory information

The focus here is on the paradoxical finding that whereas visually perceived egocentric distance is proportional to physical distance out to at least 20 m under full-cue viewing, there are large distortions of shape within the same range, reflecting a large anisotropy of depth and frontal extents on the ground plane. Three theories of visual space perception are presented, theories that are relevant to understanding this paradoxical result. The theory by Foley, Ribeiro-Filho, and Da Silva is based on the idea that when the visual system computes the length of a visible extent, the effective visual angle is a non-linear increasing function of the actual visual angle. The theory of Durgin and Li is based on the idea that two angular measures, optical slant and angular declination, are over-perceived. The theory of Ooi and He is based on both a default perceptual representation of the ground surface in the absence of visual cues and the “sequential surface integration process” whereby an internal representation of the visible ground surface is constructed starting from beneath the observer’s feet and extending outward. Keywords: visual space perception, vision, depth perception.

In studies of postural control, a control task is often used to understand significant effects obtained with experimental manipulations. This task should be the easiest task and (therefore) engage the lowest behavioral variability and cognitive workload. Since 1983, the stationary-gaze task is considered as the most relevant control task. Instead, the authors expected that free looking at small targets (white paper or images; visual angle: 12°) could be an easier task. To verify this assumption, 16 young individuals performed stationary-gaze, white-panel, and free-viewing 12° tasks in steady and relaxed stances. The stationary-gaze task led to significantly higher cognitive workload (mean score in the National Aeronotics and Space Administration Task Load Index questionnaire), higher interindividual body (head, neck, and lower back) linear variability, and higher interindividual body angular variability-not systematically yet-than both other tasks. There was more cognitive workload in steady than relaxed stances. The authors also tested if a free-viewing 24° task could lead to greater angular displacement, and hence greater body sway, than could the other tasks in relaxed stance. Unexpectedly, the participants mostly moved their eyes and not their body in this task. In the discussion, the authors explain why the stationary-gaze task may not be an ideal control task and how to choose this neutral task. 49

The ability to simultaneously attend to multiple objects declines with increases in the visual angle separating distant objects. We explored whether these laboratory-measured limits on visual attentional spread generalize to a real life context: offside calls by soccer assistant referees. We coded all offside calls from a full year of first division German soccer matches. By determining the x-y coordinates of the relevant players and assistant referee on the soccer field we were able to calculate how far assistant referees had to spread their visual attention to perform well. Counterintuitively, assistant referees made fewer errors when they were farther away from the action due to an advantageous (smaller) visual angle on the game action. The pattern held even when we accounted for individual differences in a laboratory-based attentional spread measure of ten of the assistant referees. Our finding that errors are linked to smaller visual angles may explain the complaints of fans in some situations: Those seated directly behind the assistant referee, further from the players, might actually have it easier to make the right call because the relevant players would form a smaller visual angle.