A stable representation of object size, in spite of continuous variations in retinal input due to changes in viewing distance, is critical for perceiving and acting in a real 3D world. In fact, our perceptual and visuo-motor systems exhibit size and grip constancies in order to compensate for the natural shrinkage of the retinal image with increased distance. The neural basis of this size-distance scaling remains largely unknown, although multiple lines of evidence suggest that size-constancy operations might take place remarkably early, already at the level of the primary visual cortex. In this study, we examined for the first time the temporal dynamics of size constancy during perception and action by using a combined measurement of event-related potentials (ERPs) and kinematics. Participants were asked to maintain their gaze steadily on a fixation point and perform either a manual estimation or a grasping task towards disks of different sizes placed at different distances. Importantly, the physical size of the target was scaled with distance to yield a constant retinal angle. Meanwhile, we recorded EEG data from 64 scalp electrodes and hand movements with a motion capture system. We focused on the first positive-going visual evoked component peaking at approximately 90 ms after stimulus onset. We found earlier latencies and greater amplitudes in response to bigger than smaller disks of matched retinal size, regardless of the task. In line with the ERP results, manual estimates and peak grip apertures were larger for the bigger targets. We also found task-related differences at later stages of processing from a cluster of central electrodes, whereby the mean amplitude of the P2 component was greater for manual estimation than grasping. Taken together, these findings provide novel evidence that size constancy for real objects at real distances occurs at the earliest cortical stages and that early visual processing does not change as a function of task demands.

Regardless of competitive athletes\' body image pressures, only few studies have focused on adolescent sport participants\' body image and the findings are inconclusive. Furthermore, the role of competitive goals in sports on adolescents\' body size perception has not been studied. We examined the factors associated with adolescents\' competitive goals in sports and body size perception, and the associations between adolescents\' competitive goals in sports and body size perception.
The cross-sectional study consisted of 475 goal-oriented sports club participants and 936 reference youths (aged 14-16 years). The study questionnaire included multiple choice items on health behaviours, motives to exercise, competitive goals in sports and body size perception. The multinomial logistic regression analysis was used to investigate the associations.
Adolescents with competitive goals in sports perceived their body size as about the right size more frequently than reference youths (68% vs 47%, p < 0.001 in girls; 74% vs 61%, p < 0.001 in boys). More than one-fourth of girls with competitive goals in sports perceived themselves as overweight, although only 7% of them were overweight. Adolescents with appearance/weight motives to exercise and poor perceived physical fitness had higher odds of perceived fatness. Additionally, BMI was positively associated with perceived fatness and negatively with perceived thinness. Having competitive goals in sports was not independently associated with perceived fatness or perceived thinness.
Adolescents\' BMI, appearance/weight motives to exercise, and perceived physical fitness were more strongly associated with body size perception than their competitive goals in sports. However, perceived fatness among girls with competitive goals in sports should be considered in organized sports.

We examined the associations between body mass index (BMI), weight concern, body size perception, dieting and mental distress in a population-based study of 7350 adolescents.
Cross-sectional.
Data from a Norwegian population-based cohort, The Young-HUNT3 (2006-2008) from the county of Nord-Trøndelag, Norway.
A total of 7350 adolescents (13-19 years) who had both self-reported questionnaire data and anthropometric measures.
Odds for mental distress given sex, BMI, weight concern, body size perception and dieting. Analyses were performed in binomial logistic regression models.
Compared with being overweight/obese, having weight concern, irrespective of BMI, was associated with higher OR for mental distress (MD) among boys and girls. Body size overestimation was associated with an increase in the OR for MD, in participants who were overweight/obese, had weight concern or dieted. This effect was more pronounced in boys.
Weight concern and body-size estimation are strongly associated with mental health in adolescent boys and girls. Routine assessment of adolescents\' attitudes towards their weight and body size is advised.

The Ebbinghaus illusion (EI) is an optical illusion of relative size perception that reflects the contextual integration ability in the visual modality. The current study investigated the genetic basis of two subtypes of EI, EI overestimation, and EI underestimation in humans, using quantitative genomic analyses. A total of 2825 Chinese adults were tested on their magnitudes of EI overestimation and underestimation using the method of adjustment, a standard psychophysical protocol. Heritability estimation based on common single nucleotide polymorphisms (SNPs) revealed a moderate heritability (34.3%) of EI overestimation but a nonsignificant heritability of EI underestimation. A meta-analysis of two phases (phase 1: n = 1986, phase 2: n = 839) of genome-wide association study (GWAS) discovered 1969 and 58 SNPs reaching genome-wide significance for EI overestimation and EI underestimation, respectively. Among these SNPs, 55 linkage-disequilibrium-independent SNPs were associated with EI overestimation in phase 1 with genome-wide significance and their associations could be confirmed in phase 2 cohort. Gene-based analyses found seven genes to be associated with EI overestimation at the genome-wide level, two from meta-analysis, and five from classical two-stage analysis. Overall, this study provided consistent evidence for a substantial genetic basis of the Ebbinghaus illusion.

The study aimed to assess the association between body image perception and (dis)satisfaction and sociodemographic and behavioral factors in the elderly, using multinomial logistic regression. Data were analyzed for 1686 women and 1499 men participating in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Men with less schooling and women with lower per capita income showed higher odds of underestimating their body size. Former smokers of both sexes showed higher odds of overestimating their body size; lower schooling and lower per capita income decreased these odds. Increasing age, lower per capita income, and smoking increased the odds of dissatisfaction due to thinness in men, and married marital status decreased these odds. In women, low per capita income, weekly consumption of vegetables, and smoking increased the odds of such dissatisfaction. Factors that increased the odds of dissatisfaction due to excess weight in both sexes were primary or secondary schooling and former smoking. In women, low per capita income, weak physical activity, weekly consumption of vegetables, and excessive alcohol intake also increased the odds of such dissatisfaction. The results suggest that improved living conditions and the adoption of healthy behaviors can help reduce misperceived negative body image among elderly.

We propose to interpret tasks evoking the classical Müller-Lyer illusion as one form of a conflict paradigm involving relevant (line length) and irrelevant (arrow orientation) stimulus attributes. Eight practiced observers compared the lengths of two line-arrow combinations; the length of the lines and the orientation of their arrows was varied unpredictably across trials so as to obtain psychometric and chronometric functions for congruent and incongruent line-arrow combinations. To account for decision speed and accuracy in this parametric data set, we present a diffusion model based on two assumptions: inward (outward)-pointing arrows added to a line (i) add (subtract) a separate, task-irrelevant drift component, and (ii) they reduce (increase) the distance to the barrier associated with the response identifying this line as being longer. The model was fitted to the data of each observer separately, and accounted in considerable quantitative detail for many aspects of the data obtained, including the fact that arrow-congruent responses were most prominent in the earliest RT quartile-bin. Our model gives a specific, process-related meaning to traditional static interpretations of the Müller-Lyer illusion, and combines within a single coherent framework structural and strategic mechanisms contributing to the illusion. Its central assumptions correspond to the general interpretation of geometrical-optical illusions as a manifestation of the resolution of a perceptual conflict (Day & Smith, 1989; Westheimer, 2008).

To investigate cognitive control, researchers have repeatedly employed task switching paradigms. The comparison of switch relative to repeat trials reveals longer response times and higher error rates, a pattern that has been interpreted as switching costs. Functional magnetic resonance imaging (fMRI) studies have shown the involvement of different brain modules in switching conditions, including prefrontal and parietal regions together with other sub-cortical structures. In this study, the aim was to shed light on the brain basis of cognitive control using an approach that proved useful in previous studies investigating language control in bilinguals. We examined adult participants in one simple color naming context and two task selection mixed contexts. In the first mixed selection context, participants named the color or the shape of the stimulus based on a cue word. In the second, they named the color or the size of the stimulus. It was assumed that the comparison of brain responses to the same color naming in mixed selection contexts vs. in non-selection context will reveal the of engagement of cognitive control/task selection processes. Whole brain analysis of color naming in the different contexts showed a significant main effect of context. The comparison of brain responses in several frontal, parietal and sub-cortical regions, of which some are supposedly involved in cognitive control, demonstrated an increased activation during color naming in mixed relative the simple non-mixed context. The different cognitive control modules described in this study fit with recent bilingual language control and domain general cognitive models.

This study evaluated the functional role of behavioral patterns in relational behavior in humans. The participants were five children, 9-11 years-old. A modified transposition task (size) was used, requiring active comparison patterns in order to match two relational stimulus compounds with two sample stimulus compounds. Comparison patterns were analyzed in terms of the variety of sequences and exceeding movements, the choice of relevant stimuli, and their correspondence with the size relationship between stimulus instances. Results suggest that variation in sequences and movements as well as choice for relevant stimuli influenced the establishment of relational behavior. The neglect of active comparison patterns in accounting for relational behavior is discussed.

The study was designed to evaluate the accuracy of maternally perceived baby birth size assessments as a measure of birth weight and examine factors influencing the accuracy of maternal size assessments.
Cross-sectional study.
The study is based on national data from the 2016 Ethiopian Demographic and Health Survey.
We included 1455 children who had both birth size and birth weight data.
Predictive accuracy of baby birth size for low birth weight. Level of discordance between maternally perceived birth size and birth weight including factors influencing discordance.
Mother-reported baby birth size had low sensitivity (57%) and positive predictive value (41%) to indicate low birth weight but had high specificity (89%) and negative predictive values (94%). The per cent of agreement between birth weight (<2500 g vs ≥2500 g) and maternally perceived birth size (small size vs average or above) was 86% and kappa statistics indicated a moderate level of agreement (kappa=0.41, p<0.001). Maternal age, wealth index quintile, marital status and maternal education were significant predictors of the discordance between birth size and birth weight.
Maternal assessment of baby size at birth is an inaccurate proxy indicator of low birth weight in Ethiopia. Therefore, a mother\'s recall of birth size should be used as a proxy indicator for low birth weight with caution and should take maternal characteristics into consideration.

The estimation of relative distance is a perceptual task used extensively in everyday life. This important skill suffers from biases that may be more pronounced when estimation is based on haptics. This is especially true for the blind and visually impaired, for which haptic estimation of distances is paramount but not systematically trained. We investigated whether a programmable tactile display, used autonomously, can improve distance discrimination ability in blind and severely visually impaired youngsters between 7 and 22 years-old.
Training consisted of four weekly sessions in which participants were asked to haptically find, on the programmable tactile display, the pairs of squares which were separated by the shortest and longest distance in tactile images with multiple squares. A battery of haptic tests with raised-line drawings was administered before and after training, and scores were compared to those of a control group that did only the haptic battery, without doing the distance discrimination training on the tactile display.
Both blind and severely impaired youngsters became more accurate and faster at the task during training. In haptic battery results, blind and severely impaired youngsters who used the programmable display improved in three and two tests, respectively. In contrast, in the control groups, the blind control group improved in only one test, and the severely visually impaired in no tests.
Distance discrimination skills can be trained equally well in both blind and severely impaired participants. More importantly, autonomous training with the programmable tactile display had generalized effects beyond the trained task. Participants improved not only in the size discrimination test but also in memory span tests. Our study shows that tactile stimulation training that requires minimal human assistance can effectively improve generic spatial skills.