Julie Harris

Julie Harris
University of St Andrews · School of Psychology and Neuroscience

BSc (hons) Physics, DPhil Physiology

About

189
Publications
17,470
Reads
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2,283
Citations
Additional affiliations
January 2005 - January 2016
University of St Andrews
Position
  • Professor (Full)

Publications

Publications (189)
Preprint
Employing a sensory conflict paradigm, previous research has found that vision and touch contribute, on average, equally to the visuo-tactile perception of surface texture. Our study aimed to, firstly, replicate the original findings using a comparable setup and stimulus set; secondly, examine whether equal modality contributions can also be observ...
Research
Full-text available
Research Culture Report 2021 at the University of St Andrews
Preprint
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Animal warning signals show remarkable diversity, yet subjectively appear to share visual features that make defended prey stand out and look different from more cryptic palatable species. Here we develop and apply a computational model that emulates avian visual processing of pattern and colour to Lepidopteran wing patterns to show that warning si...
Article
Full-text available
When we use virtual and augmented reality (VR/AR) environments to investigate behaviour or train motor skills, we expect that the insights or skills acquired in VR/AR transfer to real-world settings. Motor behaviour is strongly influenced by perceptual uncertainty and the expected consequences of actions. VR/AR differ in both of these aspects from...
Article
Full-text available
Two stereoscopic cues that underlie the perception of motion-in-depth (MID) are changes in retinal disparity over time (CD) and interocular velocity differences (IOVD). These cues have independent spatiotemporal sensitivity profiles, depend upon different low-level stimulus properties, and are potentially processed along separate cortical pathways....
Article
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The issue of whether visually-mediated, simple reaction time (VRT) is faster in elite athletes is contentious. Here, we examined if and how VRT is affected by gaze stability in groups of international cricketers (16 females, 28 males), professional rugby-league players (21 males), and non-sporting controls (20 females, 30 males). VRT was recorded v...
Article
Full-text available
Judging the speed of objects moving in three dimensions is important in our everyday lives because we interact with objects in a three-dimensional world. However, speed perception has been seldom studied for motion in depth, particularly when using monocular cues such as looming. Here, we compared speed discrimination, and speed change discriminati...
Article
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An apparent and common feature of aposematic patterns is that they contain a high level of achromatic (luminance) contrast, for example, many warning signals combine black spots and stripes with a lighter colour such as yellow. However, the potential importance of achromatic contrast, as distinct from colour contrast, in reducing predation has been...
Preprint
Full-text available
Judging the speed of objects moving in three dimensions is important in our everyday lives, because we interact with objects in a three-dimensional world. However, speed perception has been seldom studied for motion in depth, particularly when using monocular cues such as looming. Here, we compared speed discrimination, and speed change discriminat...
Preprint
Full-text available
Bisection tasks that require individuals to identify the midpoint of a line are often used to assess the presence of biases to spatial attention in both healthy and patient populations. These tasks have helped to uncover a phenomenon called pseudoneglect, a bias towards the left-side of space in healthy individuals. First identified in the tactile...
Article
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When we track an object moving in depth, our eyes rotate in opposite directions. This type of “disjunctive” eye movement is called horizontal vergence. The sensory control signals for vergence arise from multiple visual cues, two of which, changing binocular disparity (CD) and inter-ocular velocity differences (IOVD), are specifically binocular. Wh...
Article
Pseudoneglect is the presence of a left-ward asymmetry in spatial cognition in neurotypical individuals (Bowers & Heilman, Neuropsychologia, 18(4):491, 1980). This effect is commonly demonstrated using bisection tasks that show participants are more likely to perceive the left-side of a line as longer than in reality (Jewell & McCourt, 2000). Curre...
Conference Paper
We used an obstacle-avoidance paradigm to investigate how surface properties of obstacles affect hand movements in a reaching task. The obstacles' surfaces were made from five different materials (wood, sandpaper, sugar granules, rock salt, Astro Turf). All obstacles had the same shape, size and colour, but their surface textures differed in granul...
Article
Full-text available
Motion in depth (MID) can be cued by high-resolution changes in binocular disparity over time (CD), and low-resolution interocular velocity differences (IOVD). Computational differences between these two mechanisms suggest that they may be implemented in visual pathways with different spatial and temporal resolutions. Here, we used fMRI to examine...
Article
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Motion at constant speed in the world maps into retinal motion very differently for lateral motion and motion in depth. The former is close to linear, for the latter, constant speed objects accelerate on the retina as they approach. Motion in depth is frequently studied using speeds that are constant on the retina, and are thus not consistent with...
Data
The moving line stimulus in a standard interval of the World-Fast condition. (M4V)
Data
Psychometric functions from a representative individual participant. Dots represent participant data and the line is the psychometric fit. (A) Shows the World Fast condition fit. (B) Is the fit for the World Slow condition. (C) Is the fit for the World Control Fast condition. (D) Shows the World Control Slow condition fit. (E) Shows the Retina Fast...
Data
The moving line stimulus in a speed change interval of the World-Fast condition. (M4V)
Article
Full-text available
Motion-in-depth can be detected by using two different types of binocular cues: change of disparity (CD) and inter-ocular velocity differences (IOVD). To investigate the underlying detection mechanisms, stimuli can be constructed that isolate these cues or contain both (FULL cue). Two different methods to isolate the IOVD cue can be employed: anti-...
Article
Full-text available
Purpose: Two binocular sources of information serve motion-in-depth (MID) perception: changes in disparity over time (CD), and interocular velocity differences (IOVD). While CD requires the computation of small spatial disparities, IOVD could be computed from a much lower-resolution signal. IOVD signals therefore might still be available under con...
Article
Full-text available
An ability to predict the time-to-contact (TTC) of moving objects that become momentarily hidden is advantageous in everyday life and could be particularly so in fast-ball sports. Prediction motion (PM) experiments have sought to test this ability using tasks where a disappearing target moves toward a stationary destination. Here, we developed two...
Article
Full-text available
Countershading is a pattern of coloration thought to have evolved in order to implement camouflage. By adopting a pattern of coloration that makes the surface facing towards the sun darker and the surface facing away from the sun lighter, the overall amount of light reflected off an animal can be made more uniformly bright. Countershading could hen...
Article
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Virtual reality presents a new set of challenges and opportunities for both engineers and neuroscientists. Here we provide an overview of a programme designed by a group of psychologists, neuroscientists and VR specialists to address some of the most outstanding issues in the field ranging from the very low-level (for example, how the brain process...
Article
Full-text available
Background: Parents tend to visually assess children to determine their weight status and typically underestimate child body size. A visual tool may aid parents to more accurately assess child weight status and so support strategies to reduce childhood overweight. Body image scales (BIS) are visual images of people ranging from underweight to over...
Article
Full-text available
Background The importance of optimal and/or superior vision for participation in high-level sports remains the subject of considerable clinical research interest. Here, we examine the vision and visual history of elite/near-elite cricketers and rugby-league players. Methods Stereoacuity (TNO), colour vision, and distance (with/without pinhole) and...
Article
Full-text available
Countershading is a ubiquitous patterning of animals whereby the side that typically faces the highest illumination is darker. When tuned to specific lighting conditions and body orientation with respect to the light field, countershading minimizes the gradient of light the body reflects by counterbalancing shadowing due to illumination, and has th...
Article
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There is a growing body of evidence pointing to the existence of modality-specific timing mechanisms for encoding sub-second durations. For example, the duration compression effect describes how prior adaptation to a dynamic visual stimulus results in participants underestimating the duration of a sub-second test stimulus when it is presented at th...
Article
Full-text available
The misallocation of driver visual attention has been suggested as a major contributing factor to vehicle accidents. One possible reason is that the relatively high cognitive demands of driving limit the ability to efficiently allocate gaze. We present an experiment that explores the relationship between attentional function and visual performance...
Article
Countershading, the widespread tendency of animals to be darker on the side that receives strongest illumination, has classically been explained as an adaptation for camouflage: obliterating cues to 3D shape and enhancing background matching. However, there have only been two quantitative tests of whether the patterns observed in different species...
Article
Full-text available
Deciding what constitutes an object, and what background, is an essential task for the visual system. This presents a conundrum: averaging over the visual scene is required to obtain a precise signal for object segregation, but segregation is required to define the region over which averaging should take place. Depth, obtained via binocular dispari...
Article
Full-text available
Accurately encoding the duration and temporal order of events is essential for survival and important to everyday activities, from holding conversations to driving in fast-flowing traffic. Although there is a growing body of evidence that the timing of brief events (< 1 s) is encoded by modality-specific mechanisms, it is not clear how such mechani...
Article
Countershading (darker coloration on the part of the body exposed to a greater light intensity) is widespread in the animal kingdom and has received constant attention by evolutionary biologists since the 19th century. It may serve several different functions, camouflage being one. Here, the gradient of coloration on the body compensates the gradie...
Article
Full-text available
Differences in eye movement patterns are often found when comparing passive viewing paradigms to actively engaging in everyday tasks. Arguably, investigations into visuomotor control should therefore be most useful when conducted in settings that incorporate the intrinsic link between vision and action. We present a study that compares oculomotor b...
Article
One of the most widespread patterns of colouration in the animal kingdom is countershading, a gradation of colour in which body parts that face a higher light intensity are darker. Countershading may help counterbalance the shadowing created by directional light, and, hence, reduce 3D object recognition via shape-from-shading. There is evidence tha...
Article
Depth from binocular disparity is an important cue for segregating an object from its background, and potentially breaking camouflage. In this study we explored whether depth from disparity is hindered by luminance 'camouflage', where luminance edges on an object are not coincident with disparity-defined edges. We presented participants with random...
Data
Appendix S1. Independence of the results on the choice of reference orientation. Appendix S2. Compatibility of the three selective pressures for animals limited to horizontal orientations. Appendix S3. Studies showing non‐random orientation with respect to the sun.
Conference Paper
In driving, the misallocation of visual attention has been suggested as a major contributing factor to vehicle accidents. One possible reason for this misallocation of attention is that the relatively large cognitive demands of driving limits the ability to efficiently allocate gaze. Knowing more about how these cognitive demand characteristics inf...
Article
Many animals have a gradation of body color, termed “countershading,” where the areas that are typically exposed to more light are darker. One hypothesis is that this patterning enhances visual camouflage by making the retinal image of the animal match that of the background, a fundamentally two-dimensional theory. More controversially, countershad...
Article
Full-text available
Orientation with respect to the sun has been observed in a wide range of species and has generally been interpreted in terms of thermoregulation and/or ultraviolet (UV) protection. For countershaded animals, orientation with respect to the sun may also result from the pressure to exploit the gradient of coloration optimally to enhance crypsis. Here...
Conference Paper
In many areas, experts often exhibit specialised eye movement behaviour which allows for more efficient task execution than novices. In some areas (e.g. Radiology), showing this pattern of eye movement behaviour to novices can help cue overt visual attention to more relevant areas; which allows for more efficient task completion. We present a study...
Article
Our sensitivity to binocular disparity is exquisite under the best conditions, typically in uncluttered scenes with few small objects. Yet binocular vision can deliver a very strong impression of depth for complex, cluttered scenes with lots of objects and overlaps. How good is disparity processing under these conditions? Here we explored a novel t...
Article
Adapting to a spatially localized drifting dot stimulus results in the duration of a subsequent stimulus in the same location being underestimated. This duration compression effect is direction contingent (Curran & Benton, 2012), and likely driven by adaptation of cortical timing mechanisms. What is unclear is whether the adapted mechanisms are at...
Article
Full-text available
We present two pieces of research in the area of visual behaviour and driving. Our first study investigated if there are differences in eye movement behaviour when viewing movies of driving passively, as if one were a passenger, and driving where one controls the action via steering. One group of participants was asked to complete a passive hazard...
Article
Full-text available
Animal camouflage is a paradigmatic example of evolution by natural selection, and can only be understood in terms of adaptation to deceive the brains of potential predators and to the environment. Counter-shading is a very common pattern of coloration in the animal kingdom. Countershaded animals are darker on the side that faces a greater light in...
Conference Paper
We have developed a tablet computer game app for low vision users that can be used to introduce a platform for gaming, internet and visual rehabilitation to older users who have not had prior experience with information communication technology (ICT). Our target user group is people diagnosed with Age Related Macular Degeneration (AMD). The primary...
Conference Paper
Full-text available
Research into driving skill, particularly of hazard perception, often involves studies where participants either view pictures of driving scenarios or use movie viewing paradigms. However oculomotor strategies tend to change between active and passive tasks and attentional limitations are introduced during real driving. Here we present a study usin...
Article
Full-text available
Natural scenes contain hidden regions, or occlusions, that differ in the two eyes, resulting in monocular regions that can only be seen by one eye. Such monocular regions appear to not be suppressed but seem to be integrated into the scene percept. Here we explore how the two eyes' views are combined to represent a scene that contains monocular reg...