Assessment of Psychophysical Methods for Measuring the Critical Flicker Fusion Frequency in Yes/No Tasks by Fernandez-Alonso M, Kaspiris-Rousellis C, Innes W, Read JCA, FernandezAlonsoKaspirisRousellisInnesRead2019.pdf (0.5 MiB) - The Critical Flicker Fusion (CFF) threshold is widely used to evaluate the limits of visual temporal processing and has important practical applications in the field of display technologies. In this study, we evaluate the suitability of a novel adaptive psychophysical procedure for measuring CFF thresholds in a YES/NO task. Our results indicate that while the adaptive staircase procedure has high repeatability and is of shorter
duration when compared to the more robust constant stimuli method, its accuracy is lower, giving thresholds that were significantly higher (p<0.01) by approximately 15Hz.
Blog Archives
Stereotest Comparison: Efficacy, Reliability, and Variability of a New Glasses-Free Stereotest
Stereotest Comparison: Efficacy, Reliability, and Variability of a New Glasses-Free Stereotest by McCaslin AG, Vancleef K, Hubert L, Read JCA, Port NL, McCaslinVancleefHubertReadPort2020_compressed.pdf (0.6 MiB) - Purpose: To test the validity of the ASTEROID stereotest as a clinical test of depth perception by comparing it to clinical and research standard tests.
Methods: Thirty-nine subjects completed four stereotests twice: the ASTEROID test on an autostereo 3D tablet, a research standard on a VPixx PROPixx 3D projector, Randot Circles, and Randot Preschool. Within 14 days, subjects completed each test for a third time.
Results: ASTEROID stereo thresholds correlated well with research standard thresholds (r = 0.87, P < 0.001), although ASTEROID underestimated standard threshold (mean difference = 11 arcsec). ASTEROID results correlated less strongly with Randot Circles (r = 0.54, P < 0.001) and Randot Preschool (r = 0.64, P < 0.001), due to the greater measurement range of ASTEROID (1–1000 arcsec) compared to Randot Circles or Randot Preschool. Stereo threshold variability was low for all three clinical stereotests (Bland–Altman 95% limits of agreement between test and retest: ASTEROID, ±0.37; Randot Circles, ±0.24; Randot Preschool, ±0.23). ASTEROID captured the largest range of stereo in a normal population with test–retest reliability comparable to research standards (immediate r = 0.86 for ASTEROID vs. 0.90 for PROPixx; follow-up r = 0.68 for ASTEROID vs. 0.88 for PROPixx).
Conclusions: Compared to clinical and research standards for assessing depth perception, ASTEROID is highly accurate, has good test–retest reliability, and measures a wider range of stereo threshold.
Translational Relevance: The ASTEROID stereotest is a better clinical tool for determining baseline stereopsis and tracking changes during treatment for amblyopia and strabismus compared to current clinical tests.
Methods: Thirty-nine subjects completed four stereotests twice: the ASTEROID test on an autostereo 3D tablet, a research standard on a VPixx PROPixx 3D projector, Randot Circles, and Randot Preschool. Within 14 days, subjects completed each test for a third time.
Results: ASTEROID stereo thresholds correlated well with research standard thresholds (r = 0.87, P < 0.001), although ASTEROID underestimated standard threshold (mean difference = 11 arcsec). ASTEROID results correlated less strongly with Randot Circles (r = 0.54, P < 0.001) and Randot Preschool (r = 0.64, P < 0.001), due to the greater measurement range of ASTEROID (1–1000 arcsec) compared to Randot Circles or Randot Preschool. Stereo threshold variability was low for all three clinical stereotests (Bland–Altman 95% limits of agreement between test and retest: ASTEROID, ±0.37; Randot Circles, ±0.24; Randot Preschool, ±0.23). ASTEROID captured the largest range of stereo in a normal population with test–retest reliability comparable to research standards (immediate r = 0.86 for ASTEROID vs. 0.90 for PROPixx; follow-up r = 0.68 for ASTEROID vs. 0.88 for PROPixx).
Conclusions: Compared to clinical and research standards for assessing depth perception, ASTEROID is highly accurate, has good test–retest reliability, and measures a wider range of stereo threshold.
Translational Relevance: The ASTEROID stereotest is a better clinical tool for determining baseline stereopsis and tracking changes during treatment for amblyopia and strabismus compared to current clinical tests.
The impact of active research involvement of young children in the design of a new stereotest
The impact of active research involvement of young children in the design of a new stereotest by Casanova T, Black C, Rafiq S, Hugill-Jones J, Read JCA, Vancleef K, CasanovaBlackRafiqHugillJonesReadVancleef2020.pdf (1.4 MiB) - Background: Although considered important, the direct involvement of young children in research design is scarce and to our knowledge its impact has never been measured. We aim to demonstrate impact of young children’s involvement in improving the understanding of a new 3D eye test or stereotest.
Methods: After a pre-measure of understanding was taken, we explored issues with the test instructions in patient and public involvement (PPI) sessions where children acted as advisers in the test design. Feedback was collected via observations, rating scales and verbal comments. An interdisciplinary panel reviewed the feedback, discussed potential changes to the test design, and decided on the implementation. Subsequently, a post-measure of understanding (Study 1–2) and engagement (Study 3) was collected in a pre-post study design. Six hundred fifty children (2–11.8 years old) took part in the pre-measure, 111 children (1–12 years old) in the subsequent PPI sessions, and 52 children (4–6 years old) in the first post-measure. One hundred twenty-two children (1–12 years old) and unrelated adults took then part in a second series of PPI sessions, and 53 people (2–39 years old) in the final post-measure. Adults were involved to obtain verbal descriptions of the target that could be used to explain the task to children.
Results: Following feedback in Study 1, we added a frame cue and included a shuffle animation. This increased the percentage of correct practice trials from 76 to 97% (t (231) = 14.29, p < .001), but more encouragements like ‘Keep going!’ were needed (t (64) = 8.25, p < .001). After adding a cardboard demo in Study 2, the percentage of correct trials remained stable but the number of additional instructions given decreased (t (103) = 3.72, p < .001) as did the number of encouragements (t (103) = 8.32, p < .001). Therefore, changes in test design following children’s feedback significantly improved task understanding.
Conclusions: Our study demonstrates measurable impact of involvement of very young children in research design through accessible activities. The changes implemented following their feedback significantly improved the understanding of our test. Our approach can inform researchers on how to involve young children in research design and can contribute to developing guidelines for involvement of young children in research.
Methods: After a pre-measure of understanding was taken, we explored issues with the test instructions in patient and public involvement (PPI) sessions where children acted as advisers in the test design. Feedback was collected via observations, rating scales and verbal comments. An interdisciplinary panel reviewed the feedback, discussed potential changes to the test design, and decided on the implementation. Subsequently, a post-measure of understanding (Study 1–2) and engagement (Study 3) was collected in a pre-post study design. Six hundred fifty children (2–11.8 years old) took part in the pre-measure, 111 children (1–12 years old) in the subsequent PPI sessions, and 52 children (4–6 years old) in the first post-measure. One hundred twenty-two children (1–12 years old) and unrelated adults took then part in a second series of PPI sessions, and 53 people (2–39 years old) in the final post-measure. Adults were involved to obtain verbal descriptions of the target that could be used to explain the task to children.
Results: Following feedback in Study 1, we added a frame cue and included a shuffle animation. This increased the percentage of correct practice trials from 76 to 97% (t (231) = 14.29, p < .001), but more encouragements like ‘Keep going!’ were needed (t (64) = 8.25, p < .001). After adding a cardboard demo in Study 2, the percentage of correct trials remained stable but the number of additional instructions given decreased (t (103) = 3.72, p < .001) as did the number of encouragements (t (103) = 8.32, p < .001). Therefore, changes in test design following children’s feedback significantly improved task understanding.
Conclusions: Our study demonstrates measurable impact of involvement of very young children in research design through accessible activities. The changes implemented following their feedback significantly improved the understanding of our test. Our approach can inform researchers on how to involve young children in research design and can contribute to developing guidelines for involvement of young children in research.
Efficient estimation of stereo thresholds: What slope should be assumed for the psychometric function?
Efficient estimation of stereo thresholds: What slope should be assumed for the psychometric function? by Serrano-Pedraza I, Vancleef K, Herbert W, Goodship N, Woodhouse M, Read JCA, StrangGilmartinGrayWinfieldWinn2000.pdf (0.3 MiB) - Bayesian staircases are widely used in psychophysics to estimate detection thresholds. Simulations have revealed the importance of the parameters selected for the assumed subject's psychometric function in enabling thresholds to be estimated with small bias and high precision. One important parameter is the slope of the psychometric function, or equivalently its spread. This is often held fixed, rather than estimated for individual subjects, because much larger numbers of trials are required to estimate the spread as well as the threshold. However, if this fixed value is wrong, the threshold estimate can be biased. Here we determine the optimal slope to minimize bias and maximize precision when measuring stereoacuity with Bayesian staircases. We performed 2- and 4AFC disparity detection stereo experiments in order to measure the spread of the disparity psychometric function in human observers assuming a Logistic function. We found a wide range, between 0.03 and 3.5 log10 arcsec, with little change with age. We then ran simulations to examine the optimal spread using the empirical data. From our simulations and for three different experiments, we recommend selecting assumed spread values between the percentiles 60-80% of the population distribution of spreads (these percentiles can be extended to other type of thresholds). For stereo thresholds, we recommend a spread around the value σ = 1.7 log10 arcsec for 2AFC (slope β = 4.3 /log10 arcsec), and around σ = 1.5 log10 arcsec for 4AFC (β = 4.9 /log10 arcsec). Finally, we compared a Bayesian procedure (ZEST using the optimal σ) with five Bayesian procedures that are versions of ZEST-2D, Psi, and Psi-marginal. In general, for the conditions tested, ZEST optimal σ showed the lowest threshold bias and highest precision.
Binocular responsiveness of projection neurons of the praying mantis optic lobe in the frontal visual field
Binocular responsiveness of projection neurons of the praying mantis optic lobe in the frontal visual field by Rosner R, Tarawneh G, Lukyanova V, Read JCA, Full-text-available-for-free-at-https.txt (94 B) - Praying mantids are the only insects proven to have stereoscopic vision (stereopsis): the ability to perceive depth from the slightly shifted images seen by the two eyes. Recently, the first neurons likely to be involved in mantis stereopsis were described and a speculative neuronal circuit suggested. Here we further investigate classes of neurons in the lobula complex of the praying mantis brain and their tuning to stereoscopically-defined depth. We used sharp electrode recordings with tracer injections to identify visual projection neurons with input in the optic lobe and output in the central brain. In order to measure binocular response fields of the cells the animals watched a vertical bar stimulus in a 3D insect cinema during recordings. We describe the binocular tuning of 19 neurons projecting from the lobula complex and the medulla to central brain areas. The majority of neurons (12/19) were binocular and had receptive fields for both eyes that overlapped in the frontal region. Thus, these neurons could be involved in mantis stereopsis. We also find that neurons preferring different contrast polarity (bright vs dark) tend to be segregated in the mantis lobula complex, reminiscent of the segregation for small targets and widefield motion in mantids and other insects.
Second-order cues to figure motion enable object detection during prey capture by praying mantises
Second-order cues to figure motion enable object detection during prey capture by praying mantises by Nityananda V, O’Keeffe J, Umeton D, Simmons A, Read JCA, NityanandaOKeeffeUmetonSimmonsRead2019.pdf (1.6 MiB) - Detecting motion is essential for animals to perform a wide variety of functions. In order to do so, animals could exploit motion cues, including both first-order cues—such as luminance correlation over time—and second-order cues, by correlating higher-order visual statistics. Since first-order motion cues are typically sufficient for motion detection, it is unclear why sensitivity to second-order motion has evolved in animals, including insects. Here, we investigate the role of second-order motion in prey capture by praying mantises. We show that prey detection uses second-order motion cues to detect figure motion. We further present a model of prey detection based on second-order motion sensitivity, resulting from a layer of position detectors feeding into a second layer of elementary-motion detectors. Mantis stereopsis, in contrast, does not require figure motion and is explained by a simpler model that uses only the first layer in both eyes. Second-order motion cues thus enable prey motion to be detected, even when perfectly matching the average background luminance and independent of the elementary motion of any parts of the prey. Subsequent to prey detection, processes such as stereopsis could work to determine the distance to the prey. We thus demonstrate how second-order motion mechanisms enable ecologically relevant behavior such as detecting camouflaged targets for other visual functions including stereopsis and target tracking.
Characterizing the Randot Preschool stereotest: Testability, norms, reliability, specificity and sensitivity in children aged 2-11 years
Characterizing the Randot Preschool stereotest: Testability, norms, reliability, specificity and sensitivity in children aged 2-11 years by Read JCA, Rafiq S, Hugill J, Casanova T, Black C, O'Neill A, Puyat V, Haggerty H, Smart K, Powell C, Taylor K, Clarke MP, Vancleef K, ReadEARandotPreschool2019e.pdf (1.8 MiB) - Purpose
To comprehensively assess the Randot Preschool stereo test in young children, including testability, normative values, test/retest reliability and sensitivity and specificity for detecting binocular vision disorders.
Methods
We tested 1005 children aged 2–11 years with the Randot Preschool stereo test, plus a cover/uncover test to detect heterotropia. Monocular visual acuity was assessed in both eyes using Keeler Crowded LogMAR visual acuity test for children aged 4 and over.
Results
Testability was very high: 65% in two-year-olds, 92% in three-year-olds and ~100% in older children. Normative values: In 389 children aged 2–5 with apparently normal vision, 6% of children scored nil (stereoblind). In those who obtained a threshold, the mean log threshold was 2.06 log10 arcsec, corresponding to 114 arcsec, and the median threshold was 100 arcsec. Most older children score 40 arcsec, the best available score. We found a small sex difference, with girls scoring slightly but significantly better. Test/retest reliability: ~99% for obtaining any score vs nil. Agreement between stereo thresholds is poor in children aged 2–5; 95% limit of agreement = 0.7 log10 arcsec: five-fold change in stereo threshold may occur without any change in vision. In children over 5, the test essentially acts only as a binary classifier since almost all non-stereoblind children score 40 arcsec. Specificity (true negative rate): >95%. Sensitivity (true positive rate): poor, <50%, i.e. around half of children with a demonstrable binocular vision abnormality score well on the Randot Preschool.
Conclusions
The Randot Preschool is extremely accessible for even very young children, and is very reliable at classifying children into those who have any stereo vision vs those who are stereoblind. However, its ability to quantify stereo vision is limited by poor repeatability in children aged 5 and under, and a very limited range of scores relevant to children aged over 5.
Figures
To comprehensively assess the Randot Preschool stereo test in young children, including testability, normative values, test/retest reliability and sensitivity and specificity for detecting binocular vision disorders.
Methods
We tested 1005 children aged 2–11 years with the Randot Preschool stereo test, plus a cover/uncover test to detect heterotropia. Monocular visual acuity was assessed in both eyes using Keeler Crowded LogMAR visual acuity test for children aged 4 and over.
Results
Testability was very high: 65% in two-year-olds, 92% in three-year-olds and ~100% in older children. Normative values: In 389 children aged 2–5 with apparently normal vision, 6% of children scored nil (stereoblind). In those who obtained a threshold, the mean log threshold was 2.06 log10 arcsec, corresponding to 114 arcsec, and the median threshold was 100 arcsec. Most older children score 40 arcsec, the best available score. We found a small sex difference, with girls scoring slightly but significantly better. Test/retest reliability: ~99% for obtaining any score vs nil. Agreement between stereo thresholds is poor in children aged 2–5; 95% limit of agreement = 0.7 log10 arcsec: five-fold change in stereo threshold may occur without any change in vision. In children over 5, the test essentially acts only as a binary classifier since almost all non-stereoblind children score 40 arcsec. Specificity (true negative rate): >95%. Sensitivity (true positive rate): poor, <50%, i.e. around half of children with a demonstrable binocular vision abnormality score well on the Randot Preschool.
Conclusions
The Randot Preschool is extremely accessible for even very young children, and is very reliable at classifying children into those who have any stereo vision vs those who are stereoblind. However, its ability to quantify stereo vision is limited by poor repeatability in children aged 5 and under, and a very limited range of scores relevant to children aged over 5.
Figures
Motion-in-depth perception and prey capture in the praying mantis Sphodromantis lineola
Motion-in-depth perception and prey capture in the praying mantis Sphodromantis lineola by Nityananda V, Joubier C, Tan J, Tarawneh G, Read JCA, NityanandaJoubierTanTarawnehRead2019.pdf (0.8 MiB) - Perceiving motion-in-depth is essential to detecting approaching
or receding objects, predators and prey. This can be achieved
using several cues, including binocular stereoscopic cues such
as changing disparity and interocular velocity differences, and
monocular cues such as looming. Although these have been
studied in detail in humans, only looming responses have been well
characterized in insects and we know nothing about the role of
stereoscopic cues and how they might interact with looming cues. We
used our 3D insect cinema in a series of experiments to investigate
the role of the stereoscopic cues mentioned above, as well as
looming, in the perception of motion-in-depth during predatory strikes
by the praying mantis Sphodromantis lineola. Our results show that
motion-in-depth does increase the probability of mantis strikes but
only for the classic looming stimulus, an expanding luminance edge.
Approach indicated by radial motion of a texture or expansion of a
motion-defined edge, or by stereoscopic cues, all failed to elicit
increased striking. We conclude that mantises use stereopsis to
detect depth but not motion-in-depth, which is detected via looming.
or receding objects, predators and prey. This can be achieved
using several cues, including binocular stereoscopic cues such
as changing disparity and interocular velocity differences, and
monocular cues such as looming. Although these have been
studied in detail in humans, only looming responses have been well
characterized in insects and we know nothing about the role of
stereoscopic cues and how they might interact with looming cues. We
used our 3D insect cinema in a series of experiments to investigate
the role of the stereoscopic cues mentioned above, as well as
looming, in the perception of motion-in-depth during predatory strikes
by the praying mantis Sphodromantis lineola. Our results show that
motion-in-depth does increase the probability of mantis strikes but
only for the classic looming stimulus, an expanding luminance edge.
Approach indicated by radial motion of a texture or expansion of a
motion-defined edge, or by stereoscopic cues, all failed to elicit
increased striking. We conclude that mantises use stereopsis to
detect depth but not motion-in-depth, which is detected via looming.
Pattern and Speed Interact to Hide Moving Prey
Pattern and Speed Interact to Hide Moving Prey by Umeton D, Tarawneh G, Fezza E, Read JCA, Rowe C, UmetonTarawnehFezzaReadRowe2019.pdf (1.1 MiB) - Evolutionary biologists have long been fascinated by camouflage patterns that help animals reduce their chances of being detected by predators. However, patterns that hide prey when they remain stationary, such as those that match their backgrounds, are rendered ineffective once prey are moving. The question remains: can a moving animal ever be patterned in a way that helps reduce detection by predators? One long-standing idea is that high-contrast patterns with repeated elements, such as stripes, which are highly visible when prey are stationary, can actually conceal prey when they move fast enough [11, 12, 13, 14]. This is predicted by the “flicker fusion effect,” which occurs when prey move with sufficient speed that their pattern appears to blur, making them appear more featureless and become less conspicuous against the background [2, 8]. However, although this idea suggests a way to camouflage moving prey, it has not been empirically tested, and it is not clear that it would work at speeds that are biologically relevant to a predator [13]. Combining psychophysics and behavioral approaches, we show that speed and pattern interact to determine the detectability of prey to the praying mantis (Sphodromantis lineola) and, crucially, that prey with high-contrast stripes become less visible than prey with background-matching patterns when moving with sufficient speed. We show that stripes can reduce the detection of moving prey by exploiting the spatiotemporal limitations of predator perception, and that the camouflaging effect of a pattern depends upon the speed of prey movement.
Visual Perception: Monovision Can Bias the Apparent Depth of Moving Objects
Visual Perception: Monovision Can Bias the Apparent Depth of Moving Objects by Read JCA, ReadMonovision2019.pdf (0.6 MiB) - ‘Monovision’ — using one eye for near work and one for distance — is a common alternative to reading
glasses. New work shows that monovision can cause the distance of moving objects to be misestimated,
with potentially serious consequences
glasses. New work shows that monovision can cause the distance of moving objects to be misestimated,
with potentially serious consequences