ORCID Profile
0000-0001-9042-5536
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University of Queensland
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Psychology | Sensory Processes, Perception And Performance | Sensory Systems | Cognitive Science Not Elsewhere Classified
Publisher: SAGE Publications
Date: 2009
DOI: 10.1068/P5860
Abstract: When two identical targets move toward one another from opposite sides of a display and continue past one another along collinear trajectories, they can be perceived to either stream past or bounce off of one another. Streaming is the dominant perception in motion displays free of additional transients, while bouncing predominates when a transient (eg auditory or visual) is presented at the point of coincidence. We investigated whether the auditory induced bias towards bouncing would persist as the probability of a motion reversal was reduced by introducing a spatial offset either vertically in a 2-D display or in depth in a 3-D display. Offset conditions were combined with two auditory conditions (tone or no-tone at the point of coincidence) in the presence or absence of a central occluder. In conditions with no sound, streaming was reported on a clear majority of trials, regardless of spatial offset. When a transient tone was presented, reported motion reversals dominated and persisted for increasing verbal offsets up to 17.9 min of arc and for 3-D trajectory offsets up to 25.6 min of arc. The bounce-promoting effect of an auditory tone at the point of coincidence in stream/bounce displays persists in spite of rendering the visual motion sequence unambiguous and more consistent with streaming.
Publisher: IEEE
Date: 12-2017
Publisher: Elsevier BV
Date: 10-2006
DOI: 10.1016/J.VISRES.2006.06.020
Abstract: Grove, Gillam, and Ono [Grove, P. M., Gillam, B. J., & Ono, H. (2002). Content and context of monocular regions determine perceived depth in random dot, unpaired background and phantom stereograms. Vision Research, 42, 1859-1870] reported that perceived depth in monocular gap stereograms [Gillam, B. J., Blackburn, S., & Nakayama, K. (1999). Stereopsis based on monocular gaps: Metrical encoding of depth and slant without matching contours. Vision Research, 39, 493-502] was attenuated when the color/texture in the monocular gap did not match the background. It appears that continuation of the gap with the background constitutes an important component of the stimulus conditions that allow a monocular gap in an otherwise binocular surface to be responded to as a depth step. In this report we tested this view using the conventional monocular gap stimulus of two identical grey rectangles separated by a gap in one eye but abutting to form a solid grey rectangle in the other. We compared depth seen at the gap for this stimulus with stimuli that were identical except for two additional small black squares placed at the ends of the gap. If the squares were placed stereoscopically behind the rectangle/gap configuration (appearing on the background) they interfered with the perceived depth at the gap. However when they were placed in front of the configuration this attenuation disappeared. The gap and the background were able under these conditions to complete amodally.
Publisher: Brill
Date: 2016
DOI: 10.1163/22134808-00002524
Abstract: The ‘stream/bounce’ illusion refers to the perception of an ambiguous visual display in which two discs approach each other on a collision course. The display can be seen as two discs streaming through each other or bouncing off each other. Which perception dominates, may be influenced by a brief transient, usually a sound, presented around the time of simulated contact. Several theories have been proposed to account for the switching in dominance based on sensory processing, attention and cognitive inference, but a universally applicable, parsimonious explanation has not emerged. We hypothesized that only cognitive inference would be influenced by the perceptual history of the display. We rendered the display technically unambiguous by vertically offsetting the targets’ trajectories and manipulated their history by allowing the objects to switch from one trajectory to the other up to four times before the potential collision point. As the number of switches increased, the number of ‘bounce’ responses also increased. These observations show that expectancy is a critical factor in determining whether a bounce or streaming is perceived and may form the basis for a universal explanation of instances of the stream/bounce illusion.
Publisher: American Psychological Association (APA)
Date: 06-2021
DOI: 10.1037/XHP0000916
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-07-2013
DOI: 10.1167/13.8.11
Abstract: In visual search, target detection times are relatively insensitive to set size when targets and distractors differ on a single feature dimension. Search can be confined to only those elements sharing a single feature, such as color (Egeth, Virzi, & Garbart, 1984). These findings have been taken as evidence that elementary feature dimensions support a parallel segmentation of a scene into discrete sets of items. Here we explored if relative depth (signaled by binocular disparity) could support a similar parallel segmentation by examining the effects of distributing distracting elements across two depth planes. Three important empirical findings emerged. First, when the target was a feature singleton on the target depth plane, but a conjunction search among distractors on the nontarget plane, search efficiency increased compared to a single depth plane. Second, benefits of segmentation in depth were only observed when the target depth plane was known in advance. Third, no benefit of segmentation in depth was observed when both planes required a conjunction search, even with prior knowledge of the target depth plane. Overall, the benefit of distributing the elements of a search set across two depth planes was observed only when the two planes differed both in binocular disparity and in the elementary feature composition of in idual elements. We conclude that segmentation of the search array into two depth planes can facilitate visual search, but unlike color or other elementary properties, does not provide an automatic, preattentive segmentation.
Publisher: SAGE Publications
Date: 05-1999
DOI: 10.1068/P2908
Abstract: Two experiments were conducted to explore Gillam and Borsting's (1988, Perception17 603–608) report that uncorrelated monocular texture facilitates stereopsis by shortening the latency to see depth in random-dot stereograms. Experiment 1 used stereograms similar, in pattern but not disparity, to Gillam and Borsting's with monocular texture present or absent. A third condition, where monocular texture was dissimilar to the binocular panels and background, was also used. We were unable to generalize the findings of Gillam and Borsting for a depth step of 6 min of arc to a larger depth step of 24 min of arc. That is, we observed no significant difference in latencies between the conditions with monocular texture absent and present at a disparity of 24 min of arc. We found latencies to be significantly longer in the monocular-texture-different condition than the monocular-texture-absent condition, however. We account for this, ad hoc, by arguing that the monocular-texture-different stereogram depicts a rare or ‘accidental’ visual scenario. This account was supported by the results of experiment 2 which showed that stereograms depicting accidental views yielded longer latencies than those depicting generic views. We conclude that the ecological validity of monocular texture must also be considered when assessing the effects of monocular texture on stereopsis.
Publisher: Springer New York
Date: 15-08-2012
Publisher: SAGE Publications
Date: 03-10-2016
Abstract: The stream-bounce effect refers to a bistable motion stimulus that is interpreted as two targets either “streaming” past or “bouncing” off one another, and the manipulations that bias responses. Directional bias, according to Bertenthal et al., is an account of the effect proposing that low-level motion integration promotes streaming, and its disruption leads to bouncing, and it is sometimes cited either directly in a bottom-up fashion or indirectly under top-down control despite Sekuler and Sekuler finding evidence inconsistent with it. We tested two key aspects of the hypothesis: (a) comparable changes in speed should produce comparable disruptions and lead to similar effects and (b) speed changes alone should disrupt integration without the need for additional more complex changes of motion. We found that target motion influences stream-bounce perception, but not as directional bias predicts. Our results support Sekuler and Sekuler and argue against the low-level motion signals driving perceptual outcomes in stream-bounce displays (directly or indirectly) and point to higher level inferential processes involving perceptual history and expectation. Directional bias as a mechanism should be abandoned and either another specific bottom-up process must be proposed and tested or consideration should be given to top-down factors alone driving the effect.
Publisher: BMJ
Date: 19-02-2016
Publisher: SAGE Publications
Date: 20-07-2018
Abstract: We examined the attention and inference accounts of audiovisual perception using the stream/bounce display, a visual stimulus wherein two identical objects move toward each other, completely superimpose, then move apart. This display has two candidate percepts: stream past each other or bounce off each other. Presented without additional visual or auditory transients, the motion sequence tends to yield the streaming percept, but when coupled with a tone or flash at the point of coincidence, the response bias flips toward bouncing. We explored two competing accounts of this effect: the attentional hypothesis and the inference hypothesis. Participants watched a series of motion sequences where a transient, when present, occurred at the moment of coincidence either colocalised with the motion sequence (congruent presentation) or on the opposite side of the display (incongruent presentation). Assuming the spotlight or zoom lens metaphor, an attentional account predicts that incongruent presentations should be associated with a higher percentage of bouncing responses than congruent presentations, while the inferential account predicts the opposite effect. No effect was found for tone-only trials. However, in trials containing a visual transient, results showed higher proportions of bounce responses within congruent over incongruent presentations, favouring the inference hypothesis over a spotlight or zoom lens attentional account.
Publisher: Hindawi Limited
Date: 2014
DOI: 10.1155/2014/274803
Abstract: Hering reported that the area over which he could bifixate a target was smaller at near convergence distances than far convergence distances and predicted that in extreme horizontal gaze positions, the temporally directed eye lags behind the nasally directed eye. We tested these predictions using a subjective index of eye position. Experiment 1 confirmed that the bifixation field was significantly smaller at near convergence distances. When bifixation broke down at the near distance, the nasally directed eye lagged behind the temporally directed eye for all observers. At the far distance, the nasally directed eye preceded the temporally directed eye for four of six observers. Experiment 2 also confirmed that the bifixation field was smaller at near convergence distances but the nasally directed eye always lagged behind the temporally directed eye at the limits of the bifixation field. We confirmed Hering’s first prediction that the bifixation field is smaller at near convergence distances than at far ones. However, the majority of our results indicate that the nasally directed eye lags behind the temporally directed eye at the limits of the bifixation field, contrary to Hering’s prediction. We conclude that the eyes drift toward their tonic state of vergence when fusion breaks.
Publisher: SAGE Publications
Date: 04-10-2016
Abstract: The audiovisual stream-bounce effect refers to the resolution of ambiguous motion sequences as streaming or bouncing depending on the presence or absence of a sound. We used a novel experimental design and signal detection theory (SDT) to determine its sensory or decisional origins. To account for issues raised by Witt et al. on the interpretation of SDT results, we devised a pure signal detection (as opposed to signal discrimination) paradigm and measured participants’ sensitivity and criterion when detecting a weak tone concurrent with objectively streaming or bouncing visual displays. We observed no change in sensitivity but a significant change in criterion with participants’ criterion more liberal with bouncing targets than for streaming targets with. In a second experiment, we tasked participants with detecting a weak tone in noise while viewing an ambiguous motion sequence. They also indicated whether the targets appeared to stream or bounce. Participants’ reported equivalent, mostly bouncing responses for hit and false alarm trials, and equivalent, mostly streaming responses for correct rejection and miss trials. Further, differences in participants’ sensitivity and criterion measures for detecting tones in subjectively streaming compared to subjectively bouncing targets were inconsistent with sensory factors. These results support a decisional account of the sound-induced switch from mostly streaming to mostly bouncing responses in audiovisual stream-bounce displays.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 22-07-2014
DOI: 10.1167/14.8.16
Abstract: We aimed to show that a single auditory tone crossmodally affects multiple visual events using a multiple stream/bounce display (SBD), consisting of two disk pairs moving toward each other at equal speeds, coinciding, and then moving apart in a two-dimensional (2-D) display. The temporal offsets were manipulated between the coincidences of the disk pairs (0 to ±240 ms) by staggering motion onset between the pairs. A tone was presented at the coincidence timing of one of the disk pairs on half of the trials. Participants judged whether the disks in each of two pairs appeared to stream through or bounce off each other. Results show that a tone presented at either of the disk pairs' coincidence points promoted bouncing percepts in both disk pairs compared to no-tone trials. Perceived bouncing persisted in the disk-pair whose coincidence was offset 60 ms before and up to more than 120 ms after the audiovisual coincidence timing of the other disk-pair. The temporal window of bounce promotion was comparable to that obtained with a conventional SBD. The interaction of a single auditory event and multiple visual events was also modulated by the kind of experimental task (the stream/bounce or simultaneity judgments). These findings suggest that, using a single auditory cue, the perceptual system resolves the ambiguity of the motion of multiple disk pairs presented within the conventional temporal window of crossmodal interaction.
Publisher: Springer Science and Business Media LLC
Date: 19-08-2016
DOI: 10.1007/S00423-016-1495-Z
Abstract: Surgeons conventionally assume the optimal viewing position during 3D laparoscopic surgery and may not be aware of the potential hazards to team members positioned across different suboptimal viewing positions. The first aim of this study was to map the viewing positions within a standard operating theatre where in iduals may experience visual ghosting (i.e. double vision images) from crosstalk. The second aim was to characterize the standard viewing positions adopted by instrument nurses and surgical assistants during laparoscopic pelvic surgery and report the associated levels of visual ghosting and discomfort. In experiment 1, 15 participants viewed a laparoscopic 3D display from 176 different viewing positions around the screen. In experiment 2, 12 participants (randomly assigned to four clinically relevant viewing positions) viewed laparoscopic suturing in a simulation laboratory. In both experiments, we measured the intensity of visual ghosting. In experiment 2, participants also completed the Simulator Sickness Questionnaire. We mapped locations within the dimensions of a standard operating theatre at which visual ghosting may result during 3D laparoscopy. Head height relative to the bottom of the image and large horizontal eccentricities away from the surface normal were important contributors to high levels of visual ghosting. Conventional viewing positions adopted by instrument nurses yielded high levels of visual ghosting and severe discomfort. The conventional viewing positions adopted by surgical team members during laparoscopic pelvic operations are suboptimal for viewing 3D laparoscopic displays, and even short periods of viewing can yield high levels of discomfort.
Publisher: American Psychological Association (APA)
Date: 2003
DOI: 10.1037/0096-3445.132.2.253
Abstract: Given Leonardo's constraint that 2 opaque objects cannot be seen in the same direction, how are the regions of objects occluded to 1 eye included in perception? To answer this question, the authors presented 3-dimensional stimuli, similar to the ones that concerned Leonardo, and measured the visual directions of their monocular and binocular regions. When the distance between near and far objects was large, the nonfixated object was seen as double and blurry. Leonardo's constraint was met by seeing the near object as double and transparent or the distant object as double and superimposed. When the distance between near and far objects was small, the constraint was met by a perceptual displacement and compression of parts of the nonfixated object.
Publisher: Public Library of Science (PLoS)
Date: 04-09-2019
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 07-08-2012
DOI: 10.1167/12.8.5
Abstract: With few exceptions, the sound-induced bias toward bouncing characteristic of the stream/bounce effect has been demonstrated via subjective responses, leaving open the question whether perceptual factors, decisional factors, or some combination of the two underlie the illusion. We addressed this issue directly, using a novel stimulus and signal detection theory to independently characterize observers' sensitivity (d') and criterion (c) when discriminating between objective streaming and bouncing events in the presence or absence of a brief sound at the point of coincidence. We first confirmed that sound-induced motion reversals persist despite rendering the targets visually distinguishable by differences in texture density. Sound-induced bouncing persisted for targets differing by as many as nine just-noticeable-differences (JNDs). We then exploited this finding in our signal detection paradigm in which observers discriminated between objective streaming and bouncing events. We failed to find any difference in sensitivity (d') between sound and no-sound conditions, but we did observe a significantly more liberal criterion (c) in the sound condition than the no-sound condition. The results suggest that the auditory-induced bias toward bouncing in this context is attributable to a sound-induced shift in criterion implicating decisional processes rather than perceptual processes determining responses to these displays.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 25-05-2007
DOI: 10.1167/7.7.7
Publisher: Elsevier BV
Date: 07-2002
DOI: 10.1016/S0042-6989(02)00104-9
Abstract: It is well known that inspecting a cyclopean grating causes threshold for detecting a subsequently presented test cyclopean grating to be elevated, and that the threshold elevation is greatest at the adapting frequency. We report here that spatial frequency discrimination threshold is also elevated, but the elevation is greatest at frequencies offset from the adapting frequency, and the elevation at the adapting frequency is near-zero. We conclude that discrimination threshold is determined by the relative activity of cyclopean frequency-tuned channels, and suggest that relative activity is computed at an opponent-frequency stage. Discrimination threshold for cyclopean gratings was 2.5-4% for two observers, and remained approximately constant over the range 0.16-2.0 cycles/ degrees. Discrimination threshold for luminance-defined gratings was only slightly lower. Discrimination threshold was approximately independent of the grating's peak-to-peak disparity over a range of 45:1 for one observer and 17:1 for another. This finding as well as the low value of discrimination threshold are consistent with an opponent-process model. The dot density of every cyclopean grating used was chosen bearing in mind our finding that three or more spatial s les per grating cycle are required before s ling effects can be ignored.
Publisher: SAGE Publications
Date: 2014
DOI: 10.1068/P7513
Abstract: The stereoscopic fusion limit denotes the largest binocular disparity for which a single fused image is perceived. Several criteria can be employed when judging whether or not a stereoscopic display is fused, and this may be a factor contributing to a discrepancy in the literature. Schor, Wood, and Ogawa (1984 Vision Research, 24, 661–665) reported that fusion limits did not change as a function of bar width, while Roumes, Plantier, Menu, and Thorpe (1997 Human Factors, 39, 359–373) reported higher fusion limits for larger stimuli than for smaller stimuli. Our investigation suggests that differing criteria between the studies could contribute to this discrepancy. In experiment 1 we measured horizontal and vertical disparity fusion limits for thin bars and for the edge of an extended surface, allowing observers to use the criterion of either diplopia or rivalry when evaluating fusion for all stimuli. Fusion limits were equal for thin bars and extended surfaces in both horizontal and vertical disparity conditions. We next measured fusion limits for a range of bar widths and instructed observers to indicate which criterion they employed on each trial. Fusion limits were constant across all stimulus widths. However, there was a sharp change in criterion from diplopia to rivalry when the angular extent of the bar width exceeded about twice the fusion limit, expressed in angular terms. We conclude that stereoscopic fusion limits do not depend on stimulus size in this context, but the criterion for fusion does. Therefore, the criterion for fusion should be clearly defined in any study measuring stereoscopic fusion limits.
Publisher: SAGE Publications
Date: 2008
DOI: 10.1068/P5771
Abstract: In previous psychophysical investigations it has been reported that the angular extent over which the human visual field is served by binocular neurons in the visual cortex is limited to the central 40°. However, these reports have been primarily based on data collected with static stimuli. Here we extend this investigation to include dynamic stimuli. Interocular transfer of the rotary motion aftereffect (rMAE) was measured for three stimulus diameters: 5, 30, and 62 deg. Interocular transfer, expressed as a percentage of monocular adapt/test rMAE duration was significantly reduced for stimulus diameter of 62 deg relative to 30 and 5 deg diameters. Nevertheless, interocular transfer durations still comprised a significant percentage of same-eye adapt/test durations (46.9%), comparable to previous reports of transfer MAE durations in near-central vision. The spatial extent of binocular interaction is likely stimulus specific and is still appreciable in the far periphery for complex-motion stimuli.
Publisher: SAGE Publications
Date: 12-2003
DOI: 10.1068/P5054
Abstract: Häkkinen and Nyman (1997 Perception26 29–38) reported that perceived slant is reduced when occlusion is a possible interpretation for the visual system. We present data from three experiments that confirm and expand on their finding. Our stimuli consisted of four types of stereograms depicting white central rectangles flanked on either side by two grey rectangles. The central white rectangles varied in height, thus manipulating the polarity of the T-junction information between the central and flanking rectangles. Perceived slant was smallest or not apparent when T-junction information indicated the central rectangles were nearer than the flanking rectangles and greatest when T-junction information indicated a farther central rectangle. Slant estimates for a stimulus containing a subjective pacmen-induced central rectangle were biased towards a depth step when an occlusion interpretation was possible.
Publisher: SAGE Publications
Date: 09-2005
DOI: 10.1068/P5274
Abstract: A partially occluded contour and a slanted contour may generate identical binocular horizontal disparities. We investigated conditions promoting an occlusion resolution indicated by an illusory contour in depth along the aligned ends of horizontally disparate line sets. For a set of identical oblique lines with a constant width added to one eye's view, strength, depth, and stability of the illusory contour were poor, whereas for oblique lines of alternating orientations the illusory contours were strong, indicating a reliance on vertical size disparities rather than vertical positional disparities in generating perceived occlusion. For horizontal lines, occlusion was seen when the lines were of different lengths and absolute width disparity was invariant across the set. In all line configurations, when the additional length was on the wrong eye to be attributed to differential occlusion, lines appeared slanted consistent with their in idual horizontal disparities. This rules out monocular illusory contours as the determining factor.
Publisher: IEEE
Date: 05-2009
Publisher: Springer Science and Business Media LLC
Date: 14-05-2015
DOI: 10.3758/S13414-015-0924-3
Abstract: Many activities necessitate the deployment of attention to specific distances and directions in our three-dimensional (3D) environment. However, most research on how attention is deployed is conducted with two dimensional (2D) computer displays, leaving a large gap in our understanding about the deployment of attention in 3D space. We report how each of four parameters of 3D visual space influence visual search: 3D display volume, distance in depth, number of depth planes, and relative target position in depth. Using a search task, we find that visual search performance depends on 3D volume, relative target position in depth, and number of depth planes. Our results demonstrate an asymmetrical preference for targets in the front of a display unique to 3D search and show that arranging items into more depth planes reduces search efficiency. Consistent with research using 2D displays, we found slower response times to find targets in displays with larger 3D volumes compared with smaller 3D volumes. Finally, in contrast to the importance of target depth relative to other distractors, target depth relative to the fixation point did not affect response times or search efficiency.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-05-2019
DOI: 10.1167/19.5.7
Abstract: Previous research suggests that cognitive factors acting in a top-down manner influence the perceptual interpretation of ambiguous stimuli. To examine the temporal unfolding of these influences as a perceptual decision evolves, we have implemented a modified version of the stream-bounce display. Our novel approach allows us to track responses to stream-bounce stimuli dynamically over the entire course of the motion sequence rather than collecting a subjective report after the fact. Using a trackpad, we had participants control a cursor to track a stream-bounce target actively from start to end and measured tracking speed throughout as the dependent variable. Our paradigm replicated the typical effect of visual-only displays being associated with a streaming bias and audiovisual displays with a bouncing bias. Our main finding is a significant behavioral change preceding a perceptual decision that then predicts that decision. Specifically, for trials in which the sound was presented, tracking speeds were significantly slower starting 500 ms before the point of coincidence and presentation of the sound for bounce compared to stream responses. We suggest that behavioral response may reflect a cognitive expectation of a perceptual outcome that then biases action and the interpretation of sensory input to favor that forthcoming percept in a manner consistent with both the predictive-coding and common-coding theoretical frameworks. Our approach provides a novel behavioral corroboration of recent imaging studies that are suggestive of early brain activity in perception and action.
Publisher: Springer Science and Business Media LLC
Date: 29-01-2019
DOI: 10.3758/S13414-019-01668-W
Abstract: We tested the sensory versus decisional origins of two established audiovisual crossmodal correspondences (CMCs lightness itch and elevation itch), applying a signal discrimination paradigm to low-level stimulus features and controlling for attentional cueing. An audiovisual stimulus randomly varied along two visual dimensions (lightness: black/white elevation: high/low) and one auditory dimension (pitch: high/low), and participants discriminated either only lightness, only elevation, or both lightness and elevation. The discrimination task and the stimulus duration varied between subjects. To investigate the influence of crossmodal congruency, we considered the effect of each CMC (lightness itch and elevation itch) on the sensitivity and criterion of each discrimination as a function of stimulus duration. There were three main findings. First, discrimination sensitivity was significantly higher for visual targets paired congruently (compared with incongruently) with tones while criterion was unaffected. Second, the sensitivity increase occurred for all stimulus durations, ruling out attentional cueing effects. Third, the sensitivity increase was feature specific such that only the CMC that related to the feature being discriminated influenced sensitivity (i.e. lightness congruency only influenced lightness discrimination and elevation congruency only influenced elevation discrimination in the single and dual task conditions). We suggest that these congruency effects reflect low-level sensory processes.
Publisher: SAGE Publications
Date: 04-2001
DOI: 10.1068/P3091
Abstract: Three experiments were conducted to investigate whether a locus of binocular correspondence extends eccentrically from the vertical horopter. In experiment 1, we investigated whether the backward inclination of the vertical horopter was manifested in the angle at which readers prefer to orient the page. All observers preferred a page inclined backwards to any other orientation. This backward inclination was less than predicted from previous psychophysical reports, however. In experiment 2, we investigated the extent of binocular correspondence, defined by minimal apparent interocular horizontal motion, in the central 24 deg of the binocular field. Our data define a planar surface inclined top-away from the observer as a locus from which psychophysical corresponding points are stimulated. In experiment 3, we measured vertical adjustments required to eliminate apparent vertical motion. Together, the pattern of results from experiments 2 and 3 is most consistent with a planar surface, inclined top-away from the observer. This is consistent with Helmholtz's account of the backward inclination of the vertical horopter and expands the locus of zero horizontal disparity from a single line in the median plane to eccentric loci extending at least ±12 deg in the central binocular field.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2017
DOI: 10.1007/S00464-017-5449-5
Abstract: This is the first study to explore the effects of crosstalk from 3D laparoscopic displays on technical performance and workload. We studied crosstalk at magnitudes that may have been tolerated during laparoscopic surgery. Participants were 36 voluntary doctors. To minimize floor effects, participants completed their surgery rotations, and a laparoscopic suturing course for surgical trainees. We used a counterbalanced, within-subjects design in which participants were randomly assigned to complete laparoscopic tasks in one of six unique testing sequences. In a simulation laboratory, participants were randomly assigned to complete laparoscopic 'navigation in space' and suturing tasks in three viewing conditions: 2D, 3D without ghosting and 3D with ghosting. Participants calibrated their exposure to crosstalk as the maximum level of ghosting that they could tolerate without discomfort. The Randot® Stereotest was used to verify stereoacuity. The study performance metric was time to completion. The NASA TLX was used to measure workload. Normal threshold stereoacuity (40-20 second of arc) was verified in all participants. Comparing optimal 3D with 2D viewing conditions, mean performance times were 2.8 and 1.6 times faster in laparoscopic navigation in space and suturing tasks respectively (p< .001). Comparing optimal 3D with suboptimal 3D viewing conditions, mean performance times were 2.9 times faster in both tasks (p< .001). Mean workload in 2D was 1.5 and 1.3 times greater than in optimal 3D viewing, for navigation in space and suturing tasks respectively (p< .001). Mean workload associated with suboptimal 3D was 1.3 times greater than optimal 3D in both laparoscopic tasks (p< .001). There was no significant relationship between the magnitude of ghosting score, laparoscopic performance and workload. Our findings highlight the advantages of 3D displays when used optimally, and their shortcomings when used sub-optimally, on both laparoscopic performance and workload.
Publisher: Elsevier BV
Date: 07-2002
DOI: 10.1016/S0042-6989(02)00083-4
Abstract: Perceived depth was measured for three-types of stereograms with the colour/texture of half-occluded (monocular) regions either similar to or dissimilar to that of binocular regions or background. In a two-panel random dot stereogram the monocular region was filled with texture either similar or different to the far panel or left blank. In unpaired background stereograms the monocular region either matched the background or was different in colour or texture and in phantom stereograms the monocular region matched the partially occluded object or was a different colour or texture. In all three cases depth was considerably impaired when the monocular texture did not match either the background or the more distant surface. The content and context of monocular regions as well as their position are important in determining their role as occlusion cues and thus in three-dimensional layout. We compare coincidence and accidental view accounts of these effects.
Publisher: American Medical Association (AMA)
Date: 09-2016
Publisher: Elsevier BV
Date: 09-2004
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 24-08-2012
DOI: 10.1167/12.8.13
Abstract: Are objects moving in depth searched for efficiently? Previous studies have reported conflicting results, with some finding efficient search for only approaching motion (Franconeri & Simons, 2003), and others reporting that both approaching and receding motion are found more efficiently than static targets (Skarratt, Cole, & Gellatly, 2009). This may be due to presentation protocol differences and a confounding variable. We systematically tested the effect of the motion-in-depth presentation method and the effect of a confounding unique depth singleton on search performance. Simulating motion in depth using size scaling, changing binocular disparity, or a calibrated combination of these two depth cues, we found that search performance was affected by presentation method and that a combination of size scaling and changing disparity gives rise to the most compelling motion-in-depth perception. Exploiting this finding in Experiment 2, we found that removing the depth singleton does not affect motion-in-depth search performance. Overall, we found that search is more efficient for targets moving in depth than static targets. Approaching and receding motion had an equal advantage over static targets in target selection, shown through shallower search slopes. However, approaching motion had lower intercepts, consistent with an advantage over receding motion in later stages of processing associated with target identification and response.
Publisher: SAGE Publications
Date: 2012
DOI: 10.1068/P7091
Abstract: O'Shea and Crassini (1982, Perception & Psychophysics32 195–196) demonstrated that fusion persists for vertical lines with an orientation disparity of 8°, but diplopia is experienced in simultaneously presented horizontal lines with the same disparity. They concluded that the neural fusion process fuses larger horizontal disparities than vertical disparities. Kertesz criticised their demonstration because it did not quantify the possible motor component associated with fusing their counter-rotated images. Krekling and Blika argued that the demonstrated anisotropy is due to a disparity bias in the visual system, owing to the temporalward tilt of corresponding vertical meridians. We addressed these criticisms with a novel stimulus and presentation protocol, that rendered compensatory cyclovergence eye movements unlikely and explored a wide range of orientation disparities. We confirmed O'Shea and Crassini's vertical/horizontal anisotropy in orientation fusion limits. In addition, our measurements of vertical lines showed that the distributions of fused responses as a function of orientation disparity in the upper and lower visual fields were shifted relative to each other. Therefore, the distributions of fusible orientation disparities are wider for vertical lines than horizontal lines and are relatively shifted as predicted if the fusional range is centred around the vertical horopter.
Publisher: SAGE Publications
Date: 2012
DOI: 10.1068/P6808
Abstract: We generalised the stream/bounce effect to dynamic random element displays containing luminance- or disparity-defined targets. Previous studies investigating audio-visual interactions in this context have exclusively employed motion sequences with luminance-defined disks or squares and have focused on properties of the accompanying brief stimuli rather than the visual properties of the motion targets. We found that the presence of a brief sound temporally close to coincidence, or a visual flash at coincidence significantly promote bounce perception for motion targets defined by either luminance contrast or disparity contrast. A brief tone significantly promoted bouncing of luminance-defined targets above a no-sound baseline when it was presented at least 250 ms before coincidence and 100 ms after coincidence. A similar pattern was observed for disparity-defined targets, though the tone promoted bouncing above the no-sound baseline when presented at least 350 ms before and 300 ms after coincidence. We further explored the temporal properties of audio-visual interactions for these two display types and found that bounce perception saturated at similar durations after coincidence. The stream/bounce illusion manifests itself in dynamic random-element displays and is similar for luminance- and disparity-defined motion targets.
Publisher: SAGE Publications
Date: 09-07-2019
Abstract: Previous research has demonstrated that Panum’s fusional range increases in the periphery, and this increase is usually attributed to eccentricity. However, it is unclear whether the increase in the periphery is driven by eccentricity or separation between the stimulus and the central fixation marker. In Experiment 1, we independently measured the effects of eccentricity and stimulus separation on Panum’s fusional range for horizontal disparities. We observed significant increases in Panum’s range as eccentricity increased independently of stimulus separation. Experiment 2 revealed that the extent of Panum’s fusional range for vertical disparities increased with eccentricity independently of stimulus separation. Taken together, these results strongly support previously held conclusions that Panum’s fusional range for both horizontal and vertical disparities increases with increasing eccentricity and is little impacted by stimulus separation.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 26-06-2015
DOI: 10.1167/15.8.12
Abstract: Binocular disparities underlie precise stereoscopic depth perception but only over a finite range. At large disparities, objects appear diplopic, and depth perception is degraded. Measurements of the range of horizontal disparities for which single vision is experienced have previously been restricted to the horizontal plane of regard. We extended these mappings, in two experiments, to the upper and lower visual fields and eccentric meridians. In Experiment 1, we measured empirical corresponding points and fusional limits at identical elevations in the median plane for 20 participants. We observed a vertical shear in binocular correspondence consistent with a backward inclined empirical vertical horopter and the fusional range centered upon it. In Experiment 2, we mapped the vertical horopter and fusional limits for a second set of elevations in the median plane and at two additional eccentricities and found a similar pattern of results as in Experiment 1. For 23 of 25 participants in this study, we found that the relationship between measurements of the vertical horopter and fusional range is similar to the established relationship between Panum's fusional range and the horizontal horopter. Our data replicate previous findings that the vertical horopter is inclined top back. We are the first to illustrate that the fusional range of horizontal disparities is approximately centered upon the vertical horopter in the median plane and along eccentric meridians.
Publisher: Oxford University Press (OUP)
Date: 20-04-2017
DOI: 10.1002/BJS.10528
Abstract: This study compared precision of depth judgements, technical performance and workload using two-dimensional (2D) and three-dimensional (3D) laparoscopic displays across different viewing distances. It also compared the accuracy of 3D displays with natural viewing, along with the relationship between stereoacuity and 3D laparoscopic performance. A counterbalanced within-subjects design with random assignment to testing sequences was used. The system could display 2D or 3D images with the same set-up. A Howard–Dolman apparatus assessed precision of depth judgements, and three laparoscopic tasks (peg transfer, navigation in space and suturing) assessed performance (time to completion). Participants completed tasks in all combinations of two viewing modes (2D, 3D) and two viewing distances (1 m, 3 m). Other measures administered included the National Aeronautics and Space Administration Task Load Index (perceived workload) and the Randot® Stereotest (stereoacuity). Depth judgements were 6·2 times as precise at 1 m and 3·0 times as precise at 3 m using 3D versus 2D displays (P & 0·001). Participants performed all laparoscopic tasks faster in 3D at both 1 and 3 m (P & 0.001), with mean completion times up to 64 per cent shorter for 3D versus 2D displays. Workload was lower for 3D displays (up to 34 per cent) than for 2D displays at both viewing distances (P & 0·001). Greater viewing distance inhibited performance for two laparoscopic tasks, and increased perceived workload for all three (P & 0·001). Higher stereoacuity was associated with shorter completion times for the navigating in space task performed in 3D at 1 m (r = − 0·40, P = 0·001). 3D displays offer large improvements over 2D displays in precision of depth judgements, technical performance and perceived workload.
Publisher: American Psychological Association (APA)
Date: 2011
DOI: 10.1037/A0021920
Abstract: Figure-ground perception is typically described as seeing one surface occluding another. Figure properties, not ground properties, are considered the significant factors. In scenes, however, a near surface will often occlude multiple contours and surfaces, often at different depths, producing alignments that are improbable except under conditions of occlusion. We thus hypothesized that unrelated (high entropy) lines would tend to appear as ground in a figure-ground paradigm more often than similarly aligned ordered (low entropy) lines. We further hypothesized that for lines spanning a closed area, high line entropy should increase the hole-like appearance of that area. These predictions were confirmed in three experiments. The probability that patterned rectangles were seen as ground when alternated with blank rectangles increased with pattern entropy. A single rectangular shape appeared more hole-like when the entropy of the enclosed contours increased. Furthermore, these same contours, with the outline shape removed, gave rise to bounding illusory contours whose strength increased with contour entropy. We conclude that figure-ground and hole perception can be determined by properties of ground in the absence of any figural shape, or surround, factors.
Publisher: Brill
Date: 16-06-2021
DOI: 10.1163/22134808-BJA10054
Abstract: We examine whether crossmodal correspondences (CMCs) modulate perceptual disambiguation by considering the influence of lightness itch congruency on the perceptual resolution of the Rubin face/vase (RFV). We randomly paired a black-and-white RFV (black faces and white vase, or vice versa) with either a high or low pitch tone and found that CMC congruency biases the dominant visual percept. The perceptual option that was CMC-congruent with the tone (white/high pitch or black/low pitch) was reported significantly more often than the perceptual option CMC-incongruent with the tone (white/low pitch or black/high pitch). However, the effect was only observed for stimuli presented for longer and not shorter durations suggesting a perceptual effect rather than a response bias, and moreover, we infer an effect on perceptual reversals rather than initial percepts. We found that the CMC congruency effect for longer-duration stimuli only occurred after prior exposure to the stimuli of several minutes, suggesting that the CMC congruency develops over time. These findings extend the observed effects of CMCs from relatively low-level feature-based effects to higher-level object-based perceptual effects (specifically, resolving ambiguity) and demonstrate that an entirely new category of crossmodal factors (CMC congruency) influence perceptual disambiguation in bistability.
Publisher: IEEE
Date: 12-2013
Publisher: SAGE Publications
Date: 2010
DOI: 10.1068/P6446
Abstract: Perceived occlusion at T-junctions or illusory contours at implicit T-junctions are often modelled by using edge information without surface context. We explored the effect of closure on perceived occlusion at T-junctions. Two vertical lines separated by a gap each had six abutting horizontal lines on opposite sides forming T-junctions. These lines were either closed or not closed into pairs at the stem ends of the Ts. In experiment 1, closed T-junction stems gave a much stronger sense of occlusion at the vertical lines than unclosed ones, even though closure information was remote from the putative occlusion and local T-junction information remained constant. When the outer two T-junctions were converted to L-junctions, perceived occlusion considerably diminished. The effect of closure on illusory-contour strength for stimuli like those of experiment 1 but with the vertical lines omitted was explored in experiment 2. The two sets of horizontal lines, separated by a gap, were either closed or not closed into pairs at their outer ends. Illusory-contour strength along the vertical alignments was much greater for closed pairs. Line terminations on both sides of the gap enhanced illusory-contour strength, but whether they were collinear or not had little effect.
Start Date: 2009
End Date: 01-2011
Amount: $50,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2008
End Date: 12-2011
Amount: $181,000.00
Funder: Australian Research Council
View Funded Activity