Unveiling the invisible: receivers use object weight cues for grip force planning in handover actions.

Handover actions are part of our daily lives. Whether it is the milk carton at the breakfast table or tickets at the box office, we usually perform these joint actions without much conscious attention. The individual actions involved in handovers, that have already been studied intensively at the level of individual actions, are grasping, lifting, and transporting objects. Depending on the object's properties, actors must plan their execution in order to ensure smooth and efficient object transfer. Therefore, anticipatory grip force scaling is crucial. Grip forces are planned in anticipation using weight estimates based on experience or visual cues. This study aimed to investigate whether receivers are able to correctly estimate object weight by observing the giver's kinematics. For this purpose, handover actions were performed with 20 dyads, manipulating the participant role (giver/receiver) and varying the size and weight of the object. Due to the random presentation of the object weight and the absence of visual cues, the participants were unaware of the object weight from trial to trial. Kinematics were recorded with a motion tracking system and grip forces were recorded with customized test objects. Peak grip force rates were used as a measure of anticipated object weight. Results showed that receiver kinematics are significantly affected by object weight. The peak grip force rates showed that receivers anticipate object weight, but givers not. This supports the hypothesis that receivers obtain information about the object weight by observing giver's kinematics and integrating this information into their own action execution.

The effects of TMS over the anterior intraparietal area on anticipatory fingertip force scaling and the size-weight illusion.

When lifting an object skillfully, fingertip forces need to be carefully scaled to the object's weight, which can be inferred from its apparent size and material. This anticipatory force scaling ensures smooth and efficient lifting movements. However, even with accurate motor plans, weight perception can still be biased. In the size-weight illusion, objects of different size but equal weight are perceived to differ in heaviness, with the small object perceived to be heavier than the large object. The neural underpinnings of anticipatory force scaling to object size and the size-weight illusion are largely unknown. In this study, we tested the role of anterior intraparietal cortex (aIPS) in predictive force scaling and the size-weight illusion, by applying continuous theta burst stimulation (cTBS) prior to participants lifting objects of different sizes. Participants received cTBS over aIPS, the primary motor cortex (control area), or Sham stimulation. We found no evidence that aIPS stimulation affected the size-weight illusion. Effects were, however, found on anticipatory force scaling, where grip force was less tuned to object size during initial lifts. These findings suggest that aIPS is not involved in the perception of object weight but plays a transient role in the sensorimotor predictions related to object size. NEW & NOTEWORTHY Skilled object manipulation requires forming anticipatory motor plans according to the object's properties. Here, we demonstrate the role of anterior intraparietal sulcus (aIPS) in anticipatory grip force scaling to object size, particularly during initial lifting experience. Interestingly, this role was not maintained after continued practice and was not related to perceptual judgments measured with the size-weight illusion.

Never too little: Grip and lift forces following probabilistic weight cues in patients with writer's cramp.

OBJECTIVE: Planning of voluntary object-related movements requires the estimation of the most probable object properties. We investigated how 14 writer's cramp (WC) patients compared to 14 controls use probabilistic weight cues in a serial grip-lift task. METHODS: In every grip-lift trial, an object of either light, medium or heavy weight had to be grasped and lifted after a visual cue gave a probabilistic prediction of the object weights (e.g. 32.5% light, 67.5% medium, 0 % heavy). We determined peak (1) grip force GF, (2) load force LF, (3) grip force rate GFR, (4) load force rate LFR, while we registered brain activity with functional magnetic resonance imaging. RESULTS: In both groups, GFR, LFR and GF increased when a higher probability of heavy weights was announced. When a higher probability of light weights was indicated, controls reduced GFR, LFR and GF, while WC patients did not downscale their forces. There were no inter-group differences in blood oxygenation level dependent activation. CONCLUSIONS: WC patients could not utilize the decision range in motor planning and adjust their force in a probabilistic cued fine motor task. SIGNIFICANCE: The results support the pathophysiological model of a hyperfunctional dopamine dependent direct basal ganglia pathway in WC.

Lift observation conveys object weight distribution but partly enhances predictive lift planning.

Observation of object lifting allows updating of internal object representations for object weight, in turn enabling accurate scaling of fingertip forces when lifting the same object. Here, we investigated whether lift observation also enables updating of internal representations for an object's weight distribution. We asked participants to lift an inverted T-shaped manipulandum, of which the weight distribution could be changed, in turns with an actor. Participants were required to minimize object roll (i.e., "lift performance") during lifting and were allowed to place their fingertips at self-chosen locations. The center of mass changed unpredictably every third to sixth trial performed by the actor, and participants were informed that they would always lift the same weight distribution as the actor. Participants observed either erroneous (i.e., object rolling toward its heavy side) or skilled (i.e., minimized object roll) lifts. Lifting performance after observation was compared with lifts without prior observation and with lifts after active lifting, which provided haptic feedback about the weight distribution. Our results show that observing both skilled and erroneous lifts convey an object's weight distribution similar to active lifting, resulting in altered digit positioning strategies. However, minimizing object roll on novel weight distributions was only improved after observing error lifts and not after observing skilled lifts. In sum, these findings suggest that although observing motor errors and skilled motor performance enables updating of digit positioning strategy, only observing error lifts enables changes in predictive motor control when lifting objects with unexpected weight distributions.NEW & NOTEWORTHY Individuals are able to extract an object's size and weight by observing interactions with objects and subsequently integrate this information in their own motor repertoire. Here, we show that this ability extrapolates to weight distributions. Specifically, we highlighted that individuals can perceive an object's weight distribution during lift observation but can only partially embody this information when planning their own actions.

ASSOCIATION BETWEEN BODY WEIGHT PERCEPTION AND QUALITY OF DIET IN BRAZILIAN ADOLESCENTS.

OBJECTIVE: To evaluate the association between body weight perception and quality of diet among Brazilian adolescents. METHODS: The sample was composed of 71,740 adolescents aged from 12 to 17 years-old enrolled in the Study of Cardiovascular Risks in Adolescents (Estudo de Riscos Cardiovasculares em Adolescentes - ERICA), carried out during 2013-2014. Body weight perception was self-reported. Food consumption was assessed by food record and quality of diet index for Brazilian adolescents (DQIA-BR) was calculated, considering the balance, diversity, and diet composition. The quality of diet was compared according to weight perception for the entire sample and after stratification by nutritional status. Linear regression models were used to assess the association between body weight perception and quality of diet. RESULTS: Among the studied adolescents, 14.7 and 30.3% reported to be underweight or overweight in relation to their desired weight, respectively. Those who perceived themselves as overweight had lower quality of diet (DQIA-BR=16.0 vs. 17.4 points; p<0.001). After stratification by BMI, adolescents with normal weight (DQIA-BR=15.3 points) or overweight (DQIA-BR=16.1 points), but who perceived themselves as overweight showed lower quality of diet when compared to their peers. In adjusted analysis, overweight perception (ß= -0.51; 95%CI -0.77; -0.24) was associated to lower quality of diet. However, this association was no longer significant after stratification by BMI status. CONCLUSIONS: Body weight perception can influence the consumption of healthy foods and the quality of diet, especially for those who consider themselves overweight. However, this association is influenced by nutritional status.

Socio-Demographic Characteristics and Body Weight Perceptions of Study Participants Benefitting Most from the Feel4Diabetes Program Based on Their Anthropometric and Glycaemic Profile Changes.

The Feel4Diabetes program was comprised of a community-based screening and a two-year intervention phase aiming to prevent type 2 diabetes (T2D) in families at risk for diabetes across Europe. The current work aimed to identify the socio-demographic characteristics and body weight perceptions of participants who benefitted the most, achieving at least a 5% reduction in body weight, waist circumference and glycaemic indices (fasting plasma glucose, insulin, glycosylated haemoglobin levels), over two-year period. Following a two-stage screening procedure, 2294 high-risk parents were randomly allocated to standard care or more intensive intervention. The participants who benefitted most were living in Southern (OR 2.39-3.67, p < 0.001) and Eastern Europe (OR 1.55-2.47, p < 0.05), received more intensive intervention (OR 1.53-1.90, p = 0.002) and were younger (<40 years old) adults (OR 1.48-1.51, p < 0.05). Furthermore, individuals with tertiary education (OR 2.06, p < 0.001), who were unemployed (OR 1.62-1.68, p < 0.05) and perceived their body weight to be higher than normal (OR 1.58-3.00, p < 0.05) were more likely to benefit from the program. Lastly, males were more likely to show improvements in their glycaemic profiles compared to females (OR 1.40, p = 0.024). These findings point out the regions in Europe and the sociodemographic profile of individuals that benefitted the most in the current study, highlighting the need to prioritise regions in greater need for such interventions and also tailor future interventions to the characteristics and perceptions of the target populations.

The size-weight illusion in visual form agnosic patient DF.

The size-weight illusion is a perceptual illusion where smaller objects are judged as heavier than equally weighted larger objects. A previous informal report suggests that visual form agnosic patient DF does not experience the size-weight illusion when vision is the only available cue to object size. We tested this experimentally, comparing the magnitudes of DF's visual, kinesthetic and visual-kinesthetic size-weight illusions to those of 28 similarly-aged controls. A modified t-test found that DF's visual size-weight illusion was significantly smaller than that of controls (zcc = -1.7). A test of simple dissociation based on the Revised Standardized Difference Test found that the discrepancy between the magnitude of DF's visual and kinesthetic size-weight illusions was not significantly different from that of controls (zdcc = -1.054), thereby failing to establish a dissociation between the visual and kinesthetic conditions. These results are consistent with previous suggestions that visual form agnosia, following ventral visual stream damage, is associated with an abnormally reduced size-weight illusion. The results, however, do not confirm that this reduction is specific to the use of visual size cues to predict object weight, rather than reflecting more general changes in the processing of object size cues or in the use of predictive strategies for lifting.

Perceived match between own and observed models' bodies: influence of face, viewpoints, and body size.

People are generally unable to accurately determine their own body measurements and to translate this knowledge to identifying a model/avatar that best represents their own body. This inability has not only been related to health problems (e.g. anorexia nervosa), but has important practical implications as well (e.g. online retail). Here we aimed to investigate the influence of three basic visual features-face presence, amount of viewpoints, and observed model size-on the perceived match between own and observed models' bodies and on attitudes towards these models. Models were real-life models (Experiment 1) or avatar models based on participants' own bodies (Experiment 2). Results in both experiments showed a strong effect of model size, irrespective of participants' own body measurements. When models were randomly presented one by one, participants gave significantly higher ratings to smaller- compared to bigger-sized models. The reverse was true, however, when participants observed and compared models freely, suggesting that the mode of presentation affected participants' judgments. Limited evidence was found for an effect of facial presence or amount of viewpoints. These results add evidence to research on visual features affecting the ability to match observed bodies with own body image, which has biological, clinical, and practical implications.

The role of the anterior intraparietal sulcus and the lateral occipital cortex in fingertip force scaling and weight perception during object lifting.

Skillful object lifting relies on scaling fingertip forces according to the object's weight. When no visual cues about weight are available, force planning relies on previous lifting experience. Recently, we showed that previously lifted objects also affect weight estimation, as objects are perceived to be lighter when lifted after heavy objects compared with after light ones. Here, we investigated the underlying neural mechanisms mediating these effects. We asked participants to lift objects and estimate their weight. Simultaneously, we applied transcranial magnetic stimulation (TMS) during the dynamic loading or static holding phase. Two subject groups received TMS over either the anterior intraparietal sulcus (aIPS) or the lateral occipital area (LO), known to be important nodes in object grasping and perception. We hypothesized that TMS over aIPS and LO during object lifting would alter force scaling and weight perception. Contrary to our hypothesis, we did not find effects of aIPS or LO stimulation on force planning or weight estimation caused by previous lifting experience. However, we found that TMS over both areas increased grip forces, but only when applied during dynamic loading, and decreased weight estimation, but only when applied during static holding, suggesting time-specific effects. Interestingly, our results also indicate that TMS over LO, but not aIPS, affected load force scaling specifically for heavy objects, which further indicates that load and grip forces might be controlled differently. These findings provide new insights on the interactions between brain networks mediating action and perception during object manipulation.NEW & NOTEWORTHY This article provides new insights into the neural mechanisms underlying object lifting and perception. Using transcranial magnetic stimulation during object lifting, we show that effects of previous experience on force scaling and weight perception are not mediated by the anterior intraparietal sulcus or the lateral occipital cortex (LO). In contrast, we highlight a unique role for LO in load force scaling, suggesting different brain processes for grip and load force scaling in object manipulation.

Sensorimotor Expectations Bias Motor Resonance during Observation of Object Lifting: The Causal Role of pSTS.

Transcranial magnetic stimulation studies have highlighted that corticospinal excitability is increased during observation of object lifting, an effect termed "motor resonance." This facilitation is driven by movement features indicative of object weight, such as object size or observed movement kinematics. Here, we investigated in 35 humans (23 females) how motor resonance is altered when the observer's weight expectations, based on visual information, do not match the actual object weight as revealed by the observed movement kinematics. Our results highlight that motor resonance is not robustly driven by object weight but easily masked by a suppressive mechanism reflecting the correctness of weight expectations. Subsequently, we investigated in 24 humans (14 females) whether this suppressive mechanism was driven by higher-order cortical areas. For this, we induced "virtual lesions" to either the posterior superior temporal sulcus (pSTS) or dorsolateral prefrontal cortex (DLPFC) before having participants perform the task. Importantly, virtual lesion of pSTS eradicated this suppressive mechanism and restored object weight-driven motor resonance. In addition, DLPFC virtual lesion eradicated any modulation of motor resonance. This indicates that motor resonance is heavily mediated by top-down inputs from both pSTS and DLPFC. Together, these findings shed new light on the theorized cortical network driving motor resonance. That is, our findings highlight that motor resonance is not only driven by the putative human mirror neuron network consisting of the primary motor and premotor cortices as well as the anterior intraparietal sulcus, but also by top-down input from pSTS and DLPFC.SIGNIFICANCE STATEMENT Observation of object lifting activates the observer's motor system in a weight-specific fashion: Corticospinal excitability is larger when observing lifts of heavy objects compared with light ones. Interestingly, here we demonstrate that this weight-driven modulation of corticospinal excitability is easily suppressed by the observer's expectations about object weight and that this suppression is mediated by the posterior superior temporal sulcus. Thus, our findings show that modulation of corticospinal excitability during observed object lifting is not robust but easily altered by top-down cognitive processes. Finally, our results also indicate how cortical inputs, originating remotely from motor pathways and processing action observation, overlap with bottom-up motor resonance effects.

Information for anticipatory neuromotor control in catching under load uncertainty.

Humans employ anticipatory muscle activation when catching under conditions of load uncertainty. Questions addressed were (a) on what information referent do catchers base their anticipatory neuromotor control when catching balls of unknown weight?, and (b) how do catchers use this functional referent? Thirty-six participants caught visually identical balls dropped from 0.75 m. Participants performed 40 trials, half with knowledge of ball weight and half without. Group L caught balls with a large weight range, while group S caught balls with a smaller range of weights. EMG integrals were computed for the ball flight period in five muscles. Anticipatory EMG integrals in the unknown weight condition were normalized to anticipatory EMG integrals for the maximum, minimum and average ball weights in the known ball weight condition. We assumed participants would base anticipatory control in the unknown weight condition on similar information, regardless of group. Therefore, differences in normalized EMG integrals between groups L and S would suggest that the specific referent tested (e.g., minimum possible ball weight) was not used to scale anticipatory muscle activation under load uncertainty. Independent sample t tests ascertained differences in normalized EMG integrals between groups L and S. The results suggested that the information referent participants used to catch balls of an unknown weight was knowledge of the maximum ball weight. Participants used this referent to generate a submaximal level of anticipatory muscle activation, i.e., about 93.2% of that used to catch the heaviest ball when ball weight was known in advance.

Multiplicative-cascade dynamics supports whole-body coordination for perception via effortful touch.

Effortful touch by the hand is essential to engaging with and perceiving properties of objects. The temporal structure of whole-body coordination must reflect the prospective control that provides for both the engagement with and perception of properties of the hefted objects. In the present study, we found signatures of multifractality in the time series of fluctuations in Euclidean displacement in the participants' center of pressure (CoP) as they hefted weighted objects to perceive their heaviness and length. Comparisons of widths of the multifractal spectrums of CoP series with 32 Iterative Amplitude Adjusted Fourier Transform (IAAFT) surrogates provided evidence for multiplicative-cascade dynamics and interactivity across scales, through the continuous t-statistic comparing the original and surrogate widths (tMF). After controlling for the linear properties of CoP series and their interactions with the informational variable (i.e., the moment of inertia of the hefted objects), regression modeling of unsigned error in judgments of heaviness and length revealed that the multifractal evidence for nonlinearity (tMF) significantly influenced unsigned error. The two indicators showed opposite, task-specific effects on accuracy: accuracy in judgments of heaviness and length decreased and increased, respectively, with greater tMF. These findings suggest that multiplicative-cascade dynamics in posture play a role in prospective coordination during the engagement with objects and perception of their properties via effortful touch by the hand. Future work may elucidate how constraint(s) on exploratory kinematics influence the multifractal behavior in such suprapostural perceptual tasks as effortful touch.

The Role of Weight Perception in Race Differences in BMI Among College Graduate and Non-College Graduate Women.

OBJECTIVE: Racial differences in BMI increase with education. Weight perception may be an important factor in overweight and obesity in black women. The aim of this study was to determine the mediating role of weight underassessment on race differences in BMI in college graduates compared with non-college graduates. METHODS: Weight perception was assessed among respondents to the 2007-2014 National Health and Nutrition Examination Survey (n = 4,871). Those who had BMI-assessed overweight or obesity and self-assessed underweight or about-right weight underassessed their weight. The associations between race and BMI through weight underassessment by college graduate status were determined using a moderated mediation analysis. RESULTS: Black women had higher BMI than white women (ß = 2.72, SE = 0.28), and disparities were larger in college graduates (ß = 3.50, SE = 0.25) compared with non-college graduates (ß = 0.78, SE = 0.15). Non-college graduate black women were more likely to underassess their weight (z score = 0.43, SE = 0.05). Indirect associations between race and BMI through weight underassessment were found only among non-college graduates (z score = -0.02, SE = 0.01), but race differences in BMI remained after accounting for weight perception among college graduates and non-college graduates. CONCLUSIONS: This study demonstrates that a nuanced, intersectional understanding of weight perception and BMI among women is required to address racial disparities in obesity.

Cold and heavy: grasping the temperature-weight illusion.

The apparent heaviness of weights placed on the skin depends on their temperature. We studied the effects of such a temperature-weight illusion (TWI) on perception and action in 21 healthy volunteers. Cold (18 °C), thermal-neutral (32 °C, skin temperature) and warm (41 °C) test objects were placed onto the palm of the non-dominant hand. Their veridical mass was 350 g (light) or 700 g (heavy). Perception of heaviness was assessed with two psychophysical experiments (magnitude estimation, cross modal matching). Cold heavy objects felt about 20% heavier than thermal-neutral objects of the same mass, shape and material. In a subsequent grip-lift experiment, the test objects were grasped with a precision grip of the dominant hand and lifted off the palm of the non-dominant hand. The grip and lift forces exerted by the fingertips were recorded. The temperature of the objects had significant effects (ANOVA, p < 0.05) on the peak grip and lift forces and on the peak grip force rate (i.e., the initial force incline). The peak grip force was about 10% higher when cold heavy objects were grasped and lifted, compared to lifts of otherwise identical thermal-neutral objects. The TWI was less pronounced when light objects or warm objects were handled. In conclusion, cooling of an object increases its apparent heaviness (perception) and influences scaling of the fingertip forces during grasping and lifting (action).

Dieting for weight-control among older adults: The role of perceived health and perceived overweight status.

BACKGROUND: Despite the ever-growing literature on weight-control diets, data about dieting among older adults are scarce. PURPOSE: To describe the prevalence of weight-control dieting across age groups and weight statuses (from healthy-weight to overweight and obese). To identify cross-sectional associations of perceived health and perceived overweight status with dieting among older adults. METHODS: Secondary analyses of the second and third waves of the Midlife in the US study (MIDUS). Sample included 2588 participants (40-93 years old, 54.5% females, age = 64.4 ± 11.1 years, BMI = 28.3 ± 5.9 kg/m2). Logistic regressions were used to predict dieting across age groups (independent variables: BMI, perceived health, perceived overweight status; covariates: BMI change, education, age, race). RESULTS: As many as 15% of participants had reported dieting during the previous year. Older age was associated with less dieting among healthy weight (p = .02) and overweight (p < .001) participants, but not among participants with obesity (p = .36). Among participants younger than 75, overweight perception (vs. healthy-weight perception) was linked with higher likelihood for dieting (40-55 years: OR = 3.94[1.70-9.1]; 55-65 years: OR = 4.11[1.91-8.82]; 65-75 years: OR = 4.50[1.90-10.65]). Nevertheless, among participants older than 75, excellent (vs. good/fair/poor) perceived health was linked with higher likelihood of dieting (good vs. excellent: OR = 0.29[0.09-0.87]; fair/poor vs. excellent: OR = 0.12[0.03-0.54]). CONCLUSIONS: Older age is associated with less weight-control dieting among people without obesity. Although overweight perception may have a stronger impact on dieting during younger age, health perception may have a stronger impact on dieting during older age, suggesting that the motivation behind weight-control diets may potentially change throughout the adult lifespan.

Visual cues, expectations, and sensorimotor memories in the prediction and perception of object dynamics during manipulation.

When we grasp and lift novel objects, we rely on visual cues and sensorimotor memories to predictively scale our finger forces and exert compensatory torques according to object properties. Recently, it was shown that object appearance, previous force scaling errors, and previous torque compensation errors strongly impact our percept. However, the influence of visual geometric cues on the perception of object torques and weights in a grasp to lift task is poorly understood. Moreover, little is known about how visual cues, prior expectations, sensory feedback, and sensorimotor memories are integrated for anticipatory torque control and object perception. Here, 12 young and 12 elderly participants repeatedly grasped and lifted an object while trying to prevent object tilt. Before each trial, we randomly repositioned both the object handle, providing a geometric cue on the upcoming torque, as well as a hidden weight, adding an unforeseeable torque variation. Before lifting, subjects indicated their torque expectations, as well as reporting their experience of torque and weight after each lift. Mixed-effect multiple regression models showed that visual shape cues governed anticipatory torque compensation, whereas sensorimotor memories played less of a role. In contrast, the external torque and committed compensation errors at lift-off mainly determined how object torques and weight were perceived. The modest effect of handle position differed for torque and weight perception. Explicit torque expectations were also correlated with anticipatory torque compensation and torque perception. Our main findings generalized across both age groups. Our results suggest distinct weighting of inputs for action and perception according to reliability.

Grip Force-Load Force Coupling Is Influenced by Altered Visual Feedback about Object Kinematics.

Recent evidence suggests that visual feedback influences the adjustment of grip force to the changing load force exerted by a grasped object as it is manipulated. The current project investigated how visual feedback of object kinematics affects the coupling of grip force to load force by scaling the apparent displacements of the object viewed in virtual reality. Participants moved the object to manually track a moving virtual target. The predictability of the changing load force exerted by the object was also manipulated by altering the nature of target trajectories (and therefore the nature of object motions). When apparent object displacements increased in magnitude, grip force became more tightly coupled to load force over time. Furthermore, when load force variations were less predictable, the magnitude of apparent object displacements affected the relative degree of continuous versus intermittent coupling of grip force to load force. These findings show that visual feedback of object motion affects the ongoing dynamical coupling between grip force control and load force experienced during manipulation of a grasped object.

Bodywide fluctuations support manual exploration: Fractal fluctuations in posture predict perception of heaviness and length via effortful touch by the hand.

The human haptic perceptual system respects a bodywide organization that responds to local stimulation through full-bodied coordination of nested tensions and compressions across multiple nonoverlapping scales. Under such an organization, the suprapostural task of manually hefting objects to perceive their heaviness and length should depend on roots extending into the postural control for maintaining upright balance on the ground surface. Postural sway of the whole body should thus carry signatures predicting what the hand can extract by hefting an object. We found that fractal fluctuations in Euclidean displacement in the participants' center of pressure (CoP) contributed to perceptual judgments by moderating how the participants' hand picked up the informational variable of the moment of inertia. The role of fractality in CoP displacement in supporting heaviness and length judgments increased across trials, indicating that the participants progressively implicate their fractal scaling in their perception of heaviness and length. Traditionally, we had to measure fractality in hand movements to predict perceptual judgments by manual hefting. However, our findings suggest that we can observe what is happening at hand in the relatively distant-from-hand measure of CoP. Our findings reveal the complex relationship through which posture supports manual exploration, entailing perception of the intended properties of hefted objects (heaviness or length) putatively through the redistribution of forces throughout the body.

Association between body weight perception and quality of diet in brazilian adolescents / Associação da percepção do peso corporal com a qualidade da dieta de adolescentes brasileiros

ABSTRACT Objective: To evaluate the association between body weight perception and quality of diet among Brazilian adolescents. Methods: The sample was composed of 71,740 adolescents aged from 12 to 17 years-old enrolled in the Study of Cardiovascular Risks in Adolescents (Estudo de Riscos Cardiovasculares em Adolescentes - ERICA), carried out during 2013-2014. Body weight perception was self-reported. Food consumption was assessed by food record and quality of diet index for Brazilian adolescents (DQIA-BR) was calculated, considering the balance, diversity, and diet composition. The quality of diet was compared according to weight perception for the entire sample and after stratification by nutritional status. Linear regression models were used to assess the association between body weight perception and quality of diet. Results: Among the studied adolescents, 14.7 and 30.3% reported to be underweight or overweight in relation to their desired weight, respectively. Those who perceived themselves as overweight had lower quality of diet (DQIA-BR=16.0 vs. 17.4 points; p<0.001). After stratification by BMI, adolescents with normal weight (DQIA-BR=15.3 points) or overweight (DQIA-BR=16.1 points), but who perceived themselves as overweight showed lower quality of diet when compared to their peers. In adjusted analysis, overweight perception (β= -0.51; 95%CI -0.77; -0.24) was associated to lower quality of diet. However, this association was no longer significant after stratification by BMI status. Conclusions: Body weight perception can influence the consumption of healthy foods and the quality of diet, especially for those who consider themselves overweight. However, this association is influenced by nutritional status.

RESUMO Objetivo: Avaliar a associação entre percepção de peso corporal e qualidade da dieta de adolescentes brasileiros. Métodos: A amostra estudada foi composta de 71.740 adolescentes de 12-17 anos participantes do Estudo de Riscos Cardiovasculares em Adolescentes (ERICA) realizado entre 2013 e 2014. A percepção do peso corporal foi avaliada por questionário autoaplicável; o consumo alimentar, por recordatório alimentar; e a qualidade da dieta pelo índice de qualidade da dieta de adolescentes brasileiros (IQDA-BR), considerando o equilíbrio, a diversidade e a composição da dieta. A qualidade da dieta foi comparada de acordo com a percepção do peso para toda a amostra e após estratificação por índice de massa corpórea (IMC). Modelos de regressão linear foram utilizados para avaliar a associação entre distúrbios na percepção do peso e qualidade da dieta. Resultados: Entre os adolescentes, 14,7 e 30,3% percebiam-se abaixo ou acima do peso, respectivamente. Aqueles que se percebiam acima do peso apresentaram menor qualidade da dieta (IQDA-BR=16,0 vs. 17,4 pontos; p<0,001). Após estratificação por IMC, adolescentes com peso normal (IQDA-BR=15,3 pontos) ou excesso de peso (IQDA-BR=16,1 pontos), mas que se percebiam como acima do peso, apresentaram pior qualidade da dieta se comparados ao demais. Em análise ajustada, perceber-se acima do peso (β= -0,51; intervalo de confiança de 95% - IC95% -0,77; -0,24) foi associado a pior qualidade da dieta, porém essa associação perdeu significância após a estratificação por IMC. Conclusões: A percepção do peso corporal parece influenciar o consumo de alimentos saudáveis e a qualidade da dieta principalmente daqueles que se consideram acima do peso, contudo essa associação é influenciada pelo estado nutricional.

Low-level sensory processes play a more crucial role than high-level cognitive ones in the size-weight illusion.

The size-weight illusion (SWI) pertains to the experience of perceiving the smaller of two equally weighted objects as heavier. Competing theories to explain the illusion can be generally grouped into cognitive and sensory theories, which place more importance on top-down processing of cognitive expectations and bottom-up processing of sensory information about the size and weight of objects, respectively. The current study examined the relative contribution of these two general explanations. This was done by varying the amounts of cognitive load in a dual-task and the quality of somatosensory feedback by wearing or not wearing gloves. Participants placed their hands through a curtain inside a box so they could not see the test objects. Inside the box, they were presented with either a small or large sphere of varying weights, which they explored manually without vision. Participants provided magnitude estimates about each object's weight in four experimental conditions (no-load with gloves, no-load without gloves, low-load without gloves, and high-load without gloves). The dual-task involved the visual presentation of a cross on a computer monitor that changed in both colour and orientation. With foot pedals, the participants responded to a target colour and / or orientation, which varied across conditions, while they hefted an object. Some conditions were designed to be more cognitively taxing than others (high-load > low-load > no-load conditions). The results revealed that the strength of the SWI diminished when participants wore the gloves but did not change as cognitive load increased on the dual-task. We conclude that the illusion is more influenced by bottom-up sensory than top-down cognitive processes.