Dr Kirsten Challinor was awarded a PhD in Psychology from Macquarie University in the area of Vision Science. She has conducted post-doctoral research projects in the Neuroscience Research Group, Aston University, UK, and also in the Psychology Department at University of Sussex, UK, investigating how humans perceive motion, and how the brain processes the information it receives from the eye. From 2011to 2016, Kirsten worked at the School of Optometry and Vision Science at the University of New South Wales, teaching visual perception, psychology, statistics, evidence-based practice and research methods. She created this resource for students: statsinfocus.com and managed a blended learning project in Medicine- improving supervisor training: clinsupervisor.com. She led the adaptation of this content for Optometry Supervisors: clinsupervisor.com/optometry. Dr Challinor was a manager for a project improving the use of Evidence-based practice in Optometry. See www.eboptometry.com. Currently Kirsten conducts research and teaches at the Australian Catholic University at the Strathfield Campus in Sydney, Australia.Her research programme has two streams:Vision Science Projects: which seek to further describe and understand the neural mechanisms by which we perceive our world.Education Projects: that aim to increase skills and knowledge in evidence based areas using innovative learning and teaching methods for statistics and research methods. Her teaching covers the areas of Perception, Cognition and Neuroscience. Address: http://kirstenchallinor.com
It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks in... more It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks involves different processes, but detailed comparisons have not been made. We measured contrast-masking functions for target patches of grating (1.25 cycles, 1 cycle ...
Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast ... more Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast have been known for many years. However, these effects have largely been studied in isolation, preventing comparison of the perceived speed of stimuli across the spatiotemporal frequency surface. We present the first systematic study to establish the perceived speed of high-and low-contrast (70% and 7%) stimuli across a broad range of Fourier parameters (SFs from 0.25-8c/deg; TFs from 2-16Hz; speeds from 0.25–64deg/s). ...
Optometry and vision science : official publication of the American Academy of Optometry, Jan 17, 2015
Evidence-based practice (EBP) is an essential component of good quality, patient-centered health ... more Evidence-based practice (EBP) is an essential component of good quality, patient-centered health care. This requires practitioners to acquire EBP skills and knowledge during undergraduate and continuing education. Evidence-based practice education exists in a range of health care disciplines, including optometry. Evidence-based practice education, however, depends on relevant skills and knowledge in educators. Courses and workshops exist for the development of EBP teaching skills in some areas of health care but not in optometry. Here, we describe a pilot workshop designed to enhance the teaching of EBP and to investigate the perspectives of optometric educators on EBP including their attitudes and perceived barriers to EBP and its teaching. Twenty-seven optometric educators including 8 facilitators participated. Of these, 14 were academics (including the 8 facilitators) and 13 were practitioners. Evidence-based practice attitudes were assessed using the Evidence-Based Practice Atti...
Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast ... more Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast have been known for many years. However, these effects have largely been studied in isolation, preventing comparison of the perceived speed of stimuli across the spatiotemporal frequency surface. We present the first systematic study to establish the perceived speed of high-and low-contrast (70% and 7%) stimuli across a broad range of Fourier parameters (SFs from 0.25-8c/deg; TFs from 2-16Hz; speeds from 0.25–64deg/s). ...
Applied Vision Association Annual 2009 Meeting, 2009
Over the last ten years our understanding of early spatial vision has improved enormously. The lo... more Over the last ten years our understanding of early spatial vision has improved enormously. The long-standing model of probability summation amongst multiple independent mechanisms with static output nonlinearities responsible for masking is obsolete. It has been replaced by a much more complex network of additive, suppressive, and facilitatory interactions and nonlinearities across eyes, area, spatial frequency, and orientation that extend well beyond the classical recep-tive field (CRF). A review of a substantial body of ...
Description Bayesian models of motion perception propose that human perception of velocity is inf... more Description Bayesian models of motion perception propose that human perception of velocity is influenced both by signals from the stimulus and by a prior preference for stationarity. When velocity signals from the stimulus show little uncertainty, the prior has little effect, but as uncertainty is increased the prior exerts a greater influence, causing a more substantial reduction in the magnitude of perceived velocity. This model can successfully account for several illusions of perceived direction (Weiss et al, 2002 Nature ...
Two-stroke apparent motion offers a challenge to current theoretical models of motion processing ... more Two-stroke apparent motion offers a challenge to current theoretical models of motion processing and is thus a useful tool for investigating motion sensor input. The stimulus involves repeated presentation of two pattern frames containing a spatial displacement, with a blank inter-stimulus interval (ISI) at one of the two-frame transitions. The resulting impression of continuous motion was measured here using both direction discrimination and motion after-effect duration in order to assess the extent to which data using the two measures can be explained by a computational model without reference to attentive tracking mechanisms. The motion-energy model was found to offer a very good account of the psychophysical data using similar parameters for both tasks. The experiment was run under both photopic and scotopic retinal illumination. Data revealed that the optimum ISI for perceiving two-stroke apparent motion shifts to longer ISIs under scotopic conditions, providing evidence for a biphasic impulse response at low luminance. Best-fitting model parameters indicate that motion sensors receive inputs from temporal filters whose central temporal frequency shifts from 2.5 to 3.0 Hz at high retinal illuminance to 1.0–1.5 Hz at low retinal illuminance.
It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks in... more It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks involves different processes, but detailed comparisons have not been made. We measured contrast-masking functions for target patches of grating (1.25 cycles, 1 cycle ...
Cast shadows have been shown to provide an effective ordinal cue to the depth position of objects... more Cast shadows have been shown to provide an effective ordinal cue to the depth position of objects. In the present study, two experiments investigated the effectiveness of cast shadows in facilitating the detection of spatial contours embedded in a field of randomly placed elements. In Experiment 1, the separation between the cast shadow and the contour was systematically increased to effectively signal different contour depth positions (relative to background elements), and this was repeated for patterns in which the lighting direction was above and from below. Increasing the shadow separation improved contour detection performance, but the degree to which sensitivity changed was dependent on the lighting direction. Patterns in which the light was from above were better detected than patterns in which the lighting direction was from below. This finding is consistent with the visual system assuming a ''light-from-above rule'' when processing cast shadows. In Experiment 2, we examined the degree to which changing the shape of the cast shadow (by randomly jittering the position of local cast shadow elements) affected the ability of the visual system to rely on the cast shadow to cue the depth position of the contour. Consistent with a coarse scale analysis, we find that cast shadows remained an effective depth cue even at large degrees of element jitter. Our findings demonstrate that cast shadows provide an effective means of signaling depth, which aids the process of contour integration, and this process is largely tolerant of local variations in lighting direction.
Although body size and shape misperception (BSSM) is a common feature of anorexia nervosa, bulimi... more Although body size and shape misperception (BSSM) is a common feature of anorexia nervosa, bulimia nervosa and muscle dysmorphia, little is known about its underlying neural mechanisms. Recently, a new approach has emerged, based on the long-established non-invasive technique of perceptual adaptation, which allows for inferences about the structure of the neural apparatus responsible for alterations in visual appearance. Here, we describe several recent experimental examples of BSSM, wherein exposure to " extreme " body stimuli causes visual aftereffects of biased perception. The implications of these studies for our understanding of the neural and cognitive representation of human bodies, along with their implications for clinical practice are discussed. Creative Commons Non Commercial CC-BY-NC: This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (http://www.creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).
It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks in... more It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks involves different processes, but detailed comparisons have not been made. We measured contrast-masking functions for target patches of grating (1.25 cycles, 1 cycle ...
Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast ... more Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast have been known for many years. However, these effects have largely been studied in isolation, preventing comparison of the perceived speed of stimuli across the spatiotemporal frequency surface. We present the first systematic study to establish the perceived speed of high-and low-contrast (70% and 7%) stimuli across a broad range of Fourier parameters (SFs from 0.25-8c/deg; TFs from 2-16Hz; speeds from 0.25–64deg/s). ...
Optometry and vision science : official publication of the American Academy of Optometry, Jan 17, 2015
Evidence-based practice (EBP) is an essential component of good quality, patient-centered health ... more Evidence-based practice (EBP) is an essential component of good quality, patient-centered health care. This requires practitioners to acquire EBP skills and knowledge during undergraduate and continuing education. Evidence-based practice education exists in a range of health care disciplines, including optometry. Evidence-based practice education, however, depends on relevant skills and knowledge in educators. Courses and workshops exist for the development of EBP teaching skills in some areas of health care but not in optometry. Here, we describe a pilot workshop designed to enhance the teaching of EBP and to investigate the perspectives of optometric educators on EBP including their attitudes and perceived barriers to EBP and its teaching. Twenty-seven optometric educators including 8 facilitators participated. Of these, 14 were academics (including the 8 facilitators) and 13 were practitioners. Evidence-based practice attitudes were assessed using the Evidence-Based Practice Atti...
Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast ... more Variations of perceived speed with spatial frequency (SF), temporal frequency (TF), and contrast have been known for many years. However, these effects have largely been studied in isolation, preventing comparison of the perceived speed of stimuli across the spatiotemporal frequency surface. We present the first systematic study to establish the perceived speed of high-and low-contrast (70% and 7%) stimuli across a broad range of Fourier parameters (SFs from 0.25-8c/deg; TFs from 2-16Hz; speeds from 0.25–64deg/s). ...
Applied Vision Association Annual 2009 Meeting, 2009
Over the last ten years our understanding of early spatial vision has improved enormously. The lo... more Over the last ten years our understanding of early spatial vision has improved enormously. The long-standing model of probability summation amongst multiple independent mechanisms with static output nonlinearities responsible for masking is obsolete. It has been replaced by a much more complex network of additive, suppressive, and facilitatory interactions and nonlinearities across eyes, area, spatial frequency, and orientation that extend well beyond the classical recep-tive field (CRF). A review of a substantial body of ...
Description Bayesian models of motion perception propose that human perception of velocity is inf... more Description Bayesian models of motion perception propose that human perception of velocity is influenced both by signals from the stimulus and by a prior preference for stationarity. When velocity signals from the stimulus show little uncertainty, the prior has little effect, but as uncertainty is increased the prior exerts a greater influence, causing a more substantial reduction in the magnitude of perceived velocity. This model can successfully account for several illusions of perceived direction (Weiss et al, 2002 Nature ...
Two-stroke apparent motion offers a challenge to current theoretical models of motion processing ... more Two-stroke apparent motion offers a challenge to current theoretical models of motion processing and is thus a useful tool for investigating motion sensor input. The stimulus involves repeated presentation of two pattern frames containing a spatial displacement, with a blank inter-stimulus interval (ISI) at one of the two-frame transitions. The resulting impression of continuous motion was measured here using both direction discrimination and motion after-effect duration in order to assess the extent to which data using the two measures can be explained by a computational model without reference to attentive tracking mechanisms. The motion-energy model was found to offer a very good account of the psychophysical data using similar parameters for both tasks. The experiment was run under both photopic and scotopic retinal illumination. Data revealed that the optimum ISI for perceiving two-stroke apparent motion shifts to longer ISIs under scotopic conditions, providing evidence for a biphasic impulse response at low luminance. Best-fitting model parameters indicate that motion sensors receive inputs from temporal filters whose central temporal frequency shifts from 2.5 to 3.0 Hz at high retinal illuminance to 1.0–1.5 Hz at low retinal illuminance.
It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks in... more It is clear that masking from parallel surrounds (doughnuts) and superimposed orthogonal masks involves different processes, but detailed comparisons have not been made. We measured contrast-masking functions for target patches of grating (1.25 cycles, 1 cycle ...
Cast shadows have been shown to provide an effective ordinal cue to the depth position of objects... more Cast shadows have been shown to provide an effective ordinal cue to the depth position of objects. In the present study, two experiments investigated the effectiveness of cast shadows in facilitating the detection of spatial contours embedded in a field of randomly placed elements. In Experiment 1, the separation between the cast shadow and the contour was systematically increased to effectively signal different contour depth positions (relative to background elements), and this was repeated for patterns in which the lighting direction was above and from below. Increasing the shadow separation improved contour detection performance, but the degree to which sensitivity changed was dependent on the lighting direction. Patterns in which the light was from above were better detected than patterns in which the lighting direction was from below. This finding is consistent with the visual system assuming a ''light-from-above rule'' when processing cast shadows. In Experiment 2, we examined the degree to which changing the shape of the cast shadow (by randomly jittering the position of local cast shadow elements) affected the ability of the visual system to rely on the cast shadow to cue the depth position of the contour. Consistent with a coarse scale analysis, we find that cast shadows remained an effective depth cue even at large degrees of element jitter. Our findings demonstrate that cast shadows provide an effective means of signaling depth, which aids the process of contour integration, and this process is largely tolerant of local variations in lighting direction.
Although body size and shape misperception (BSSM) is a common feature of anorexia nervosa, bulimi... more Although body size and shape misperception (BSSM) is a common feature of anorexia nervosa, bulimia nervosa and muscle dysmorphia, little is known about its underlying neural mechanisms. Recently, a new approach has emerged, based on the long-established non-invasive technique of perceptual adaptation, which allows for inferences about the structure of the neural apparatus responsible for alterations in visual appearance. Here, we describe several recent experimental examples of BSSM, wherein exposure to " extreme " body stimuli causes visual aftereffects of biased perception. The implications of these studies for our understanding of the neural and cognitive representation of human bodies, along with their implications for clinical practice are discussed. Creative Commons Non Commercial CC-BY-NC: This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (http://www.creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).
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