Journal of Vision最新文献

In order to fully process items of interest, we use information from outside the fovea to plan the target of the next saccadic eye movement. There is growing evidence that our initial preview of the identity and features of the saccade target, prior to bringing it to the fovea using the saccade, is used to make our subsequent post-saccadic processing more efficient. However, the mechanisms underlying trans-saccadic previews remain unknown. We investigated this in a gaze-contingent preview paradigm in which a face stimulus either remained the same ("valid preview") or changed ("invalid preview") during the saccadic eye movement. On some trials, a brief blank gap was added at the beginning of the new fixation, before the face was presented at the fovea. Although the expected preview benefit was found when the face stimulus was present after the saccade, the addition of the blank period eliminated the preview effect. Our results suggest that the preview effect relies on a sensorimotor prediction about both "what" will be present at the fovea after the saccade and "when" the new fixation will begin. These findings provided further evidence for an active, predictive mechanism for trans-saccadic perception.

Previous research has shown that observers can make reliable judgments about the relative mass of moving objects that collide in animated displays. One popular explanation of this is that observers' judgments are based on an internal model of Newtonian dynamics. An alternative explanation is that these judgments are based on measurable optical properties that are correlated with relative mass. To better understand this issue, the present investigation reanalyzed the data from three previous studies by Mitko and Fischer (2023), Sanborn et al. (2013), and Todd and Warren (1982), and it replicated an additional study by Hamrick et al. (2016). These new analyses demonstrate that observers' judgments of relative mass are most likely based on the post-collision optical velocities of objects without having to invoke an implausible mental representation of Newtonian dynamics as has been argued by several previous investigators.

The low prevalence effect, which posits that people are more likely to miss a present target when its prevalence rate is low, has important implications for real-world scenarios such as cancer screening and bomb detection. This effect has primarily been studied under full visibility; however, real-world scenarios often come with incomplete visibility. Occlusion and poor visibility introduce perceptual uncertainty, potentially altering how people decide whether a target is present. Here, we applied Bayesian decision theory to a visual search paradigm with partial occlusion, examining how target prevalence (prior) and the degree of occlusion (likelihood information) affect search decisions. Participants made target present/absent responses to target/distractor stimuli. In Experiment 1, all items were invisible, forcing participants to rely on trial feedback to learn the target's prevalence. Experiment 2 also provided trial feedback, but allowed either a small or large portion of the display to be visible. Target prevalence varied between blocks (high, 50%; low, 25%). Results showed that, when items were entirely hidden, participants learned to probability match the target's prevalence. However, when some items were visible, participants rarely responded present when the target was in the occluded region. Comparing the data with models (e.g., probability matching, Bayesian maximizing) revealed mixed strategies. This study introduces a novel method for investigating visual search under occlusion and suggests that, although people integrate prevalence and sensory input, their decisions are not fully Bayesian.

Density information is a possible primitive for the perception of numerosity. It has been argued, however, that the perception of numerosity is more precise than density perception at low numbers, whereas density is more precise for high numbers. An interpretive problem with the stimuli used to make those claims is that actual stimulus density was often mis-specified owing to an ambiguity regarding the idealized versus actual filled area. This ambiguity had the effect of underestimating density precision at low numerosities. Here we used a novel method of stimulus generation that allows us to accurately specify stimulus density independent of patch size and number, while varying patch size from trial to trial to dissociate numerosity and density. For both numerosity discrimination and density discrimination, we presented single stimuli in central vision for comparison with an internal standard. Feedback was given after each judgment. Using well-defined densities, density discrimination was more precise than numerosity perception at all densities and showed no evidence of varying as a function of density, as previously hypothesized. This was found with 8 practiced observers, and then replicated in a pre-registered study with 32 observers. As expected, feedback nullified size biases on number judgments, showing that observers were adaptively combining density and size. Reanalysis of data from a recent investigation of downward sloping Weber fractions for numerosity showed that the square root-like effects in those sorts of studies were most likely owing to reductions in patch size variance that were correlated with increases in density.

Cortically induced blindness (CB) resulting from stroke damage to the early visual cortex leads to extensive, typically extrafoveal visual deficits and is known to alter large-scale oculomotor behavior. Here, we show that even with preserved foveal acuity, fixational oculomotor behavior is subtly altered in CB patients. Using high-precision eye tracking, we observed a small but consistent gaze offset toward the blind field during passive fixation, which disappeared during a high-acuity central task. Despite this offset, fixation precision in both tasks was comparable, and it was similar between CB patients and age-matched controls. Curiously, the underlying oculomotor dynamics were also similar across the two task conditions: Microsaccades exhibited nonsignificant directional tendencies, while ocular drift was biased away from the blind field. Our findings indicate that the adult oculomotor system dynamically adapts to asymmetric visual injury and/or input. We speculate that the small fixational offsets observed in CB may reflect an attentional pointer toward the blind field and/or a compensatory oculomotor rebalancing that counteracts an asymmetric visual drive following cortical damage. Together, these results reveal a surprising preservation of context-dependent fixation control following early visual cortex damage in adulthood.

Visual ensemble perception involves the rapid global extraction of summary statistics (e.g., average features) from groups of items, without requiring single-item recognition and working memory resources. One theory that helps explain global visual perception is the principle of feature diagnosticity. This is when informative bottom-up visual features are preferentially processed to complete the task at hand by being consistent with one's top-down expectations. Past literature has studied ensemble perception using groups of objects and faces and has shown that both low-level (e.g., average color, orientation) and high-level visual statistics (e.g., average crowd animacy, object economic value) can be efficiently extracted. However, no study has explored whether summary statistics can be extracted from stimuli higher in visual complexity, necessitating global, gist-based processing for perception. To investigate this, across five experiments we had participants extract various summary statistical features from ensembles of real-world scenes. We found that average scene content (i.e., perceived naturalness or manufacturedness of scene ensembles) and average spatial boundary (i.e., perceived openness or closedness of scene ensembles) could be rapidly extracted within 125 ms, without reliance on working memory. Interestingly, when we rotated the scenes, average scene orientation could not be extracted, likely because the perception of diagnostic edge information (i.e., cardinal edges for typically encountered upright scenes) was disrupted when rotating the scenes. These results suggest that ensemble perception is a flexible resource that can be used to extract summary statistical information across multiple stimulus types but also has limitations based on the principle of feature diagnosticity in global visual perception.

Our visual system usually provides a unique and functional representation of the external world. At times, however, there is more than one compelling interpretation of the same retinal stimulus; in this case, neural populations compete for perceptual dominance to resolve ambiguity. Spatial and temporal context can guide this perceptual experience. Recent evidence shows that ambiguous retinal stimuli are sometimes resolved by enhancing either similarities or differences among multiple ambiguous stimuli. Although rivalry has traditionally been attributed to differences in stimulus strength, color vision introduces nonlinearities that are difficult to reconcile with luminance-based models. Here, it is shown that a tuned, divisive normalization framework can explain how perceptual selection can flexibly yield either similarity-based "grouped" percepts or difference-enhanced percepts during binocular rivalry. Empirical and simulated results show that divisive normalization can account for perceptual representations of either similarity enhancement (so-called grouping) or difference enhancement, offering a unified framework for opposite perceptual outcomes.

Binocular rivalry occurs when two eyes are presented with two conflicting stimuli. Although the physical stimulation stays the same, the conscious percept changes over time. This property makes it a unique paradigm in both vision science and consciousness research. Two key parameters, contrast and attention, were repeatedly shown to affect binocular rivalry dynamics in a similar manner. This was taken as evidence that attention acts by enhancing effective stimulus contrast. Brief transition periods between the two clear percepts have so far been much less investigated. In a previous study we demonstrated that transition periods can appear in different forms depending on the stimulus type and the observer. In the current study, we investigated how attention and contrast affect transition appearance. Observers viewed binocular rivalry and reported their perception of the four most common transition types by a button press while either the stimulus contrast or the locus of exogenous attention was manipulated. We show that contrast and attention similarly affect the overall binocular rivalry dynamics, but their effects on the appearance of transitions differ. These results suggest that the effect of attention is different from a simple enhancement of stimulus strength, which becomes evident only when different transition types are considered.

Online vision testing enables efficient data collection from diverse participants, but often requires accurate fixation. When needed, fixation accuracy is traditionally ensured by using a camera to track gaze. That works well in the laboratory, but tracking during online testing with a built-in webcam is not yet sufficiently precise. Kurzawski, Pombo, et al. (2023) introduced a fixation task that improves fixation through hand-eye coordination, requiring participants to track a moving crosshair with a mouse-controlled cursor. This dynamic fixation task greatly reduces peeking at peripheral targets relative to a stationary fixation task, but does not eliminate it. Here, we introduce a crowded dynamic fixation task that further enhances fixation by adding clutter around the fixation mark. We assessed fixation accuracy during peripheral threshold measurement. Relative to the root mean square gaze error during the stationary fixation task, the dynamic fixation error was 55%, whereas the crowded dynamic fixation error was only 40%. With a 1.5° tolerance, peeking occurred on 7% of trials with stationary fixation, 1.5% with dynamic fixation, and 0% with crowded dynamic fixation. This improvement eliminated implausibly low peripheral thresholds, likely by preventing peeking. We conclude that crowded dynamic fixation provides accurate gaze control for online testing.

This study examines the temporal and spatial components of microsaccade dynamics in homonymous hemianopia (HH) after ischemic stroke, and their association with patients' visual impairments. The eye position data were recorded during visual field testing in 15 patients with HH and 15 controls. Microsaccade rate (temporal) and direction (spatial) dynamics in HH were analyzed across visual field sectors with varying defect depth and compared with controls. Support vector machines were trained to characterize the visual field defects in HH based on microsaccade dynamics. Patients exhibited stronger microsaccadic inhibition in the sighted areas, postponed and stronger microsaccadic inhibition in areas of residual vision (ARVs) compared to controls. Meanwhile, a rebound was evident in the sighted areas but absent in the ARVs and blind areas. Microsaccades surviving the inhibition were more attracted toward the stimulus, whereas microsaccades after the inhibition were directed away from the stimulus in controls. Such pattern was not observed in HH. Dissociated temporal and spatial impairments of microsaccade dynamics suggest multi-fold impairments of the visual and oculomotor networks in HH. Based on the microsaccadic phase signature underlying microsaccade rate dynamics, we characterized patients' visual field defects and discovered regions with residual function inside both the blind and sighted hemifields. These findings suggest that monitoring microsaccade dynamics may provide valuable supplementary information beyond that captured by behavioral responses.