New Approaches to Visual Scale and Visual Shape

Human 3D vision is thought to triangulate the size, distance, direction, and 3D shape of objects using vision from the two eyes. But all four of these capacities rely on the visual system knowing where the eyes are pointing. Dr Linton's experimental work on size and distance challenge this account, suggesting a purely retinal account of visual size and distance, and likely direction and 3D shape. This requires new accounts of visual scale and visual shape. For visual scale, he argues that observers rely on natural scene statistics to associate accentuated stereo depth (largely from horizontal disparities) with closer distances. This implies that depth / shape is resolved before size and distance. For visual shape, he argues that depth / shape from the two eyes is a solution to a different problem (rivalry eradication between two retinal images treated as if they are from the same viewpoint), rather than the visual system attempting to infer scene geometry (by treating the two retinal images as two different views of the same scene from different viewpoints). Dr Linton also draws upon his book, which questions whether other depth cues (perspective, shading, motion) really have any influence on this process.

Ethnicity, migration, and weight misperception: a Born in Bradford study

Background: Weight perception may differ by ethnicity but is not well-understood, particularly among migrants to the United Kingdom (UK). It is also unknown whether a figure rating scale (FRS) or perceived weight question (PWQ) is more accurate for assessing body weight perception. Methods: At 24-months postpartum, women in the Born in Bradford cohort (Bradford, UK) completed the 9-item Stunkard FRS and a 7-category PWQ. Both scales were condensed to weight categories representing the World Health Organisation cut-offs. Weighted kappa statistics assessed agreement between measured and perceived weight categories. Chi-squared and Fisher's exact tests assessed categories of misperception by ethnicity and migration and logistic regression was used to examine odds of underestimation. Results: Thirty percent of white British and 23% of Pakistani-origin women had obesity. Agreement between measured and perceived weight categories were similar for white British women using either a visual scale or weight question (FRS: Kappa; [95%CI]: 0.61 [0.56, 0.65]; PWQ: 0.61 [0.55, 0.68)]. Overall agreement was lower for Pakistani-origin women with the visual scale performing better (FRS (0.58 [0.52, 0.63]) vs PWQ (0.47 [0.40, 0.54]). Pakistani-origin women, particularly those born outside the UK, were more likely to underestimate their body weight compared to white British women; this was greater with the PWQ (18% vs 10%; p<0.001) than FRS (14% vs 6%; p<0.001). Pakistani-origin women were 154% more likely to underestimate their body weight compared to white British women with the FRS and 111% more likely to underestimate when using the PWQ. Conclusion: We observed ethnic differences in weight misperception with Pakistani-origin women more likely to underestimate their weight compared to white British women. Our findings suggest visual scales, rather than perceived weight questions, are more appropriate for the self-assessment of body weight.

Does Vergence Affect Perceived Size?

Since Kepler (1604) and Descartes (1637), it has been suggested that ‘vergence’ (the angular rotation of the eyes) plays a key role in size constancy. However, this has never been tested divorced from confounding cues such as changes in the retinal image. In our experiment, participants viewed a target which grew or shrank in size over 5 s. At the same time, the fixation distance specified by vergence was reduced from 50 to 25 cm. The question was whether this change in vergence affected the participants’ judgements of whether the target grew or shrank in size? We found no evidence of any effect, and therefore no evidence that eye movements affect perceived size. If this is correct, then our finding has three implications. First, perceived size is much more reliant on cognitive influences than previously thought. This is consistent with the argument that visual scale is purely cognitive in nature (Linton, 2017; 2018). Second, it leads us to question whether the vergence modulation of V1 contributes to size constancy. Third, given the interaction between vergence, proprioception, and the retinal image in the Taylor illusion, it leads us to ask whether this cognitive approach could also be applied to multisensory integration.

The Strasbourg Visual Scale: A Novel Method to Assess Visual Hallucinations

The experience of oneself in the world is based on sensory afferences, enabling us to reach a first-perspective perception of our environment and to differentiate oneself from the world. Visual hallucinations may arise from a difficulty in differentiating one's own mental imagery from externally-induced perceptions. To specify the relationship between hallucinations and the disorders of the self, we need to understand the mechanisms of hallucinations. However, visual hallucinations are often under reported in individuals with psychosis, who sometimes appear to experience difficulties describing them. We developed the “Strasbourg Visual Scale (SVS),” a novel computerized tool that allows us to explore and capture the subjective experience of visual hallucinations by circumventing the difficulties associated with verbal descriptions. This scale reconstructs the hallucinated image of the participants by presenting distinct physical properties of visual information, step-by-step to help them communicate their internal experience. The strategy that underlies the SVS is to present a sequence of images to the participants whose choice at each step provides a feedback toward re-creating the internal image held by them. The SVS displays simple images on a computer screen that provide choices for the participants. Each step focuses on one physical property of an image, and the successive choices made by the participants help them to progressively build an image close to his/her hallucination, similar to the tools commonly used to generate facial composites. The SVS was constructed based on our knowledge of the visual pathways leading to an integrated perception of our environment. We discuss the rationale for the successive steps of the scale, and to which extent it could complement existing scales.

Visual Scale as a Non-Invasive Method for Evaluation of Risk and Severity of Coronary Atherosclerosis

Aim To evaluate quantitative and qualitative characteristics of atherosclerotic plaques (ASP) in carotid arteries (CA) and femoral arteries (FA) and to use these data for developing a visual scale (VS) for noninvasive diagnosis and determination of severity of coronary atherosclerosis.Material and methods This study included 216 patients (115 men and 101 women) aged 24 to 87 years (mean age, 61.5±10.73 years). All patients underwent coronary angiography (CAG) for detecting and determining severity of CA atherosclerosis and duplex scanning (DS) for detecting atherosclerosis of CA and FA.Results Analysis of ultrasound parameters of ASP in CA and FA showed that the maximal ASP height, moderate stenosis and maximal stenosis of the arterial bed had higher predictive values than other ultrasound parameters. These parameters were used for forming diagnostic complexes, on the basis of which two individual VSs for CA and FA were developed. Based on the high prognostic value of both scales, they were combined into one that was named VSCOMB. A ROC analysis determined cut-off points of the VSCOMB for diagnosis of CA atherosclerosis of various severity. VSCOMB scores >4 indicated pronounced CA atherosclerosis with sensitivity of 86.1 % and specificity of 87.5 % whereas VSCOMB scores ≤4 excluded it. Thus, VSCOMB score 0–1 indicated the absence of CA atherosclerosis; score 2–4 indicated the presence of subclinical CA atherosclerosis; and score >4 indicated severe CA atherosclerosis.Conclusion A VSCOMB was developed that includes a set of ultrasound parameters for CA and FA and is useful for noninvasive diagnosis of CA atherosclerosis of various severity. Simple and convenient use of VSCOMB allows it to be used at the screening stage to detect subclinical CA atherosclerosis and to prevent its progression.

CT Image Analysis Using Grayscale Statistics to Categorise Severity of Lung Abnormalities of COVID-19 Patients

Grayscale image attributes from 456 images extracted from CT scan slices of 53 patients (49 with COVID-19 and 4 without) are used to establish a visual scale of severity of lung abnormalities (five classes: 0 to 4). The complex trends of these easy-to-derive image attributes can be used graphically to discern the visual scale of lung abnormalities in broad terms. With the aid of machine learning algorithms, the visual classes can be distinguished with close to 95% accuracy using combinations of selected grayscale attributes. Confusion matrices reveal that the best-performing machine learning models are able to distinguish more accurately between certain classes than visual inspection of CT images by experts. The adaboost, decision tree and random forest models confused on average less than 25 of the 456 CT-scan image extracts evaluated between the visual classes of lung abnormalities.

Perception of smile attractiveness by dentistry professionals, dental students and laypeople before and after esthetic procedures

Dentist community needs to understand the esthetic perception of laypeople and correlate the standards of dental esthetics to avoid unnecessary treatment. Thus, the aim was to compare the perception of smile attractiveness before and after performing esthetic dental procedures by general practitioners (GP), periodontists (P), restorative dentistry (RD), undergraduate students (UGrad), and laypeople (L). Two photographs of smile were taken, before (PSB) and after (PSA) the esthetic dental procedures. Photographs were exposed to 5 groups: GP (n = 20), P (n = 20), RD (n = 20), UGrad (n = 60), and L (n = 20). The smiles were evaluated using the visual scale with scores ranging from 1 (unattractive) to 10 (very attractive). Data were statistically evaluated (Kruskal-Wallis, Dunn, Mann Whitney). The PSA of the esthetic dental procedures was more attractive than PSB (p < 0.05). In PSB, P group presented the lowest values of smile attractiveness scores (p < 0.05). On the other hand, in PSA, RD group attributed lower values (p < 0.05). The perception of smile attractiveness after performing dental procedures was higher than before, and P and RD were more critical in evaluating the smiles before and after treatment, respectively.