Prior knowledge biases the visual memory of body postures.

Body postures provide information about others' actions, intentions, and emotions. Little is known about how postures are represented in the visual system. Considering our extensive visual and motor experience with body postures, we hypothesized that priors derived from this experience may systematically bias visual body posture representations. We examined two priors: gravity and biomechanical constraints. Gravity pushes body parts downward, while biomechanical constraints limit the range of possible postures (e.g., an arm raised far behind the head cannot go down further). Across three experiments (N = 246), we probed participants' visual memory of briefly presented postures using change discrimination and adjustment tasks. Results showed that lifted arms were misremembered as lower and as more similar to the nearest biomechanically plausible postures. Inverting the body stimuli eliminated both biases, ruling out visual confounds. These findings show that visual memory representations of body postures are modulated by a combination of category-general and category-specific priors.

Converging evidence that left extrastriate body area supports visual sensitivity to social interactions.

Navigating our complex social world requires processing the interactions we observe. Recent psychophysical and neuroimaging studies provide parallel evidence that the human visual system may be attuned to efficiently perceive dyadic interactions. This work implies, but has not yet demonstrated, that activity in body-selective cortical regions causally supports efficient visual perception of interactions. We adopt a multi-method approach to close this important gap. First, using a large fMRI dataset (n = 92), we found that the left hemisphere extrastriate body area (EBA) responds more to face-to-face than non-facing dyads. Second, we replicated a behavioral marker of visual sensitivity to interactions: categorization of facing dyads is more impaired by inversion than non-facing dyads. Third, in a pre-registered experiment, we used fMRI-guided transcranial magnetic stimulation to show that online stimulation of the left EBA, but not a nearby control region, abolishes this selective inversion effect. Activity in left EBA, thus, causally supports the efficient perception of social interactions.

Predictive Processing of Scene Layout Depends on Naturalistic Depth of Field.

Boundary extension is a classic memory illusion in which observers remember more of a scene than was presented. According to predictive-processing accounts, boundary extension reflects the integration of visual input and expectations of what is beyond a scene's boundaries. According to normalization accounts, boundary extension rather reflects one end of a normalization process toward a scene's typically experienced viewing distance, such that close-up views give boundary extension but distant views give boundary contraction. Here, across four experiments (N = 125 adults), we found that boundary extension strongly depends on depth of field, as determined by the aperture settings on a camera. Photographs with naturalistic depth of field led to larger boundary extension than photographs with unnaturalistic depth of field, even when distant views were shown. We propose that boundary extension reflects a predictive mechanism with adaptive value that is strongest for naturalistic views of scenes. The current findings indicate that depth of field is an important variable to consider in the study of scene perception and memory.

Asymmetric visual representation of sex from facial appearance.

We efficiently infer others' traits from their faces, and these inferences powerfully shape our social behaviour. Here, we investigated how sex is represented in facial appearance. Based on previous findings from sex-judgment tasks, we hypothesized that the perceptual encoding of sex is not balanced but rather polarized: for the processes that generate a sex percept, the default output is "male," and the representation of female faces extends that of the male, engaging activity over unique detectors that are not activated by male faces. We tested this hypothesis with the logic of Treisman's studies of visual search asymmetries, predicting that observers should more readily detect the presence of female faces amongst male distractors than vice versa. Across three experiments (N = 32 each), each using different face stimuli, we confirmed this prediction in response time and sensitivity measures. We apply GIST analyses to the face stimuli to exclude that the search asymmetry is explained by differences in image homogeneity. These findings demonstrate a property of the coding that links facial appearance with a significant social trait: the female face is coded as an extension of a male default. We offer a mechanistic description of perceptual detectors to account for our findings and posit that the origins of this polarized coding scheme are an outcome of biased early developmental experience.

Asymmetric visual representation of sex from human body shape.

We efficiently infer others' states and traits from their appearance, and these inferences powerfully shape our social behaviour. One key trait is sex, which is strongly cued by the appearance of the body. What are the visual representations that link body shape to sex? Previous studies of visual sex judgment tasks find observers have a bias to report "male", particularly for ambiguous stimuli. This finding implies a representational asymmetry - that for the processes that generate a sex percept, the default output is "male", and "female" is determined by the presence of additional perceptual evidence. That is, female body shapes are positively coded by reference to a male default shape. This perspective makes a novel prediction in line with Treisman's studies of visual search asymmetries: female body targets should be more readily detected amongst male distractors than vice versa. Across 10 experiments (N = 32 each) we confirmed this prediction and ruled out alternative low-level explanations. The asymmetry was found with profile and frontal body silhouettes, frontal photographs, and schematised icons. Low-level confounds were controlled by balancing silhouette images for size and homogeneity, and by matching physical properties of photographs. The female advantage was nulled for inverted icons, but intact for inverted photographs, suggesting reliance on distinct cues to sex for different body depictions. Together, these findings demonstrate a principle of the perceptual coding that links bodily appearance with a significant social trait: the female body shape is coded as an extension of a male default. We conclude by offering a visual experience account of how these asymmetric representations arise in the first place.

Perceiving emotion and sex from the body: evidence from the Garner task for independent processes.

The appearance of the body signals socially relevant states and traits, but the how these cues are perceived is not well understood. Here we examined judgments of emotion and sex from the body's appearance. Understanding how we extract these cues is important because they are both salient and socially relevant. Participants viewed body images and either reported the emotion expressed by each body while ignoring its sex, or else reported the sex while ignoring its emotion. Following Garner's logic, two types of blocks were compared. In control blocks, the task-irrelevant dimension was fixed (e.g. all male in an emotion judgment task), whereas in orthogonal blocks it varied orthogonally to the task-relevant dimension (e.g. male-female). Where two dimensions draw on shared processes, interference results in relatively slower responses during orthogonal blocks. In contrast, a finding of no Garner interference - efficient selection of the task-relevant dimension - is taken to reflect independent processes. Bayesian analyses revealed evidence of no Garner interference between sex and emotion judgments, showing that extraction of these distinct signals from the body's appearance proceeds along largely parallel processing streams. These findings are informative about the mental architecture behind our perception of socially relevant characteristics of other people.

The enfacement illusion boosts facial mimicry.

Facial mimicry, the automatic imitation of another person's emotion, is a mechanism underlying emotion recognition and emotional contagion, a phylogenetically conserved form of empathy that precedes later developing empathic skills. We tested the possibility to increase facial mimicry by blurring self-other distinction via the enfacement illusion. To do so we delivered synchronous, versus asynchronous, visuo-tactile interpersonal multisensory stimulation on the observer and expresser's faces and then recorded surface facial EMG while participants observed videos of happy and sad facial expressions displayed by the expresser. Our results show that synchronous visuo-tactile stimulation can indeed enhance facial mimicry and that this depends on participants' baseline tendency to mimic.. Our findings could set the basis for developing novel interventions for conditions characterized by reduced empathic and emotion recognition skills, including autism and schizophrenia.

Causal Evidence for Expression of Perceptual Expectations in Category-Selective Extrastriate Regions.

Expectations about a visual event shape the way it is perceived [1-4]. For example, expectations induced by valid cues signaling aspects of a visual target can improve judgments about that target, relative to invalid cues [5, 6]. Such expectation effects are thought to arise via pre-activation of a template in neural populations that represent the target [7, 8] in early sensory areas [9] or in higher-level regions. For example, category cues ("face" or "house") modulate pre-target fMRI activity in associated category-selective brain regions [10, 11]. Further, a relationship is sometimes found between the strength of template activity and success in perceptual tasks on the target [12-14]. However, causal evidence linking pre-target activity with expectation effects is lacking. Here we provide such evidence, using fMRI-guided online transcranial magnetic stimulation (TMS). In two experiments, human volunteers made binary judgments about images of either a body or a scene. Before each target image, a verbal cue validly or invalidly indicated a property of the image, thus creating perceptual expectations about it. To disrupt these expectations, we stimulated category-selective visual brain regions (extrastriate body area, EBA; occipital place area, OPA) during the presentation of the cue. Stimulation ended before the target images appeared. We found a double dissociation: TMS to EBA during the cue period removed validity effects only in the body task, whereas stimulating OPA removed validity effects only in the scene task. Perceptual expectations are expressed by the selective activation of relevant populations within brain regions that encode the target.

Interactor's body shape does not affect visuo-motor interference effects during motor coordination.

The biological-tuning of the Action Observation Network is highly debated. A current open question relates to whether the morphological appearance (body shape) and/or the biological motion of the observed agent triggers action simulation processes. Motor simulation of the partner's action is critical for motor interactions, where two partners coordinate their actions in space and time. It supports interpersonal alignment and facilitates online coordination. However, motor simulation also leads to visuo-motor interference effects when people are required to coordinate with complementary actions, i.e. incongruent movements as compared to the observed ones. Movement kinematics of interactive partners allows us to capture their automatic tendency to simulate and imitate the partner's complementary movements. In an online reach-to-grasp task, we investigated whether visuo-motor interference effects, visible in the kinematics of complementary movements, are modulated by the visual presence of the interactor's body shape. We asked participants to interact with 1) a humanoid agent with a human-like body shape and with real human, biological, movement kinematics, or 2) a non-humanoid agent, which did not resemble the human body-shape but moved with the same real kinematics. Through the combination of inferential and Bayesian statistics, the results show no effect of interactor's body shape on visuo-motor interference in reaching and grasping kinematics during online motor coordination. We discuss the results and propose that the kinematics of the observed movements, during motor interactions, might be the key factor for visuo-motor interference to take place independently from the morphological appearance of the partner. This is particularly relevant in a technological society that constantly asks humans to interact with artificial agents.

Inhibition of left anterior intraparietal sulcus shows that mutual adjustment marks dyadic joint-actions in humans.

Creating real-life dynamic contexts to study interactive behaviors is a fundamental challenge for the social neuroscience of interpersonal relations. Real synchronic interpersonal motor interactions involve online, inter-individual mutual adaptation (the ability to adapt one's movements to those of another in order to achieve a shared goal). In order to study the contribution of the left anterior Intra Parietal Sulcus (aIPS) (i.e. a region supporting motor functions) to mutual adaptation, here, we combined a behavioral grasping task where pairs of participants synchronized their actions when performing mutually adaptive imitative and complementary movements, with the inhibition of activity of aIPS via non-invasive brain stimulation. This approach allowed us to investigate whether aIPS supports online complementary and imitative interactions. Behavioral results showed that inhibition of aIPS selectively impairs pair performance during complementary compared to imitative interactions. Notably, this effect depended on pairs' mutual adaptation skills and was higher for pairs composed of participants who were less capable of adapting to each other. Thus, we provide the first causative evidence for a role of the left aIPS in supporting mutually adaptive interactions and show that the inhibition of the neural resources of one individual of a pair is compensated at the dyadic level.

Sudden Onset of Lower Abdominal Pain Without Peritonitis or Ileus.

A patient presented with sudden, unexplained lower abdominal pain without peritonism or signs of infection or inflammatory reaction, but with recent bloody stools and a history of radiation therapy, diabetes and immunosuppression. Plain abdominal x-ray showed only air-fluid levels and air distention of the colon, but a later abdominal CT scan revealed extensive gas gangrene of the colon. The patient's clinical status rapidly worsened. Elective surgical rectosigmoid debridement did not prevent the patient's death. In conclusion, the diagnosis of 'spontaneous' life-threatening gas gangrene requires a high degree of clinical suspicion and allows life-saving surgical intervention. LEARNING POINTS: Sudden and rapidly worsening lower abdominal pain without peritonitis or ileus can indicate gas gangrene from distal bowel perforation.Bloody stools or other symptoms and/or procedures reported previously and apparently resolved could indicate hidden perforation.Diagnostic gas detection, clinically or radiologically, occurs too late to prevent fatal consequences, so early signs of infection and inflammation should be sought for and evaluated as early surgery is life saving.

Nível de capacitação e informação dos operadores de máquinas para a aplicação de agrotóxicos / Training and information level of operators machinery for pesticide application

O Brasil é o maior consumidor mundial de agrotóxicos. Os prejuízos causados pelo uso inadequado dos agrotóxicos ultrapassam o campo econômico, ganhando dimensão social e exigindo elevadas verbas públicas e privadas para atendimento médico hospitalar das pessoas que entram em contato, direto ou indireto, com esses produtos. O nível de conhecimento do operador das máquinas destinadas a esse fim é fundamental para diminuir esses riscos, garantindo qualidade da pulverização. Esse trabalho objetivou verificar o nível de instrução dos operadores com relação ao manejo dos agrotóxicos e máquinas destinadas a pulverização desses insumos, na região central do Rio Grande do Sul. Observou-se que os operadores que realizaram cursos com duração maior que 20 horas, apresentaram um nível de instrução 50% maior, se comparado aos operadores que receberam cursos com menos de 20 horas de duração. Já os operadores que realizaram cursos com duração menor que 20 horas apresentaram uma diferença de apenas quatro pontos percentuais, em relação aos operadores que não realizaram nenhum tipo de treinamento. O nível de instrução dos operadores de máquinas destinadas à pulverização de agrotóxicos na Região Central do Rio Grande do Sul pode ser considerado insuficiente para o manejo correto dos processos de pulverização.

Brazil is the world's largest consumer of pesticides. The damage caused by improper use of pesticides beyond the economic field are gaining social dimension, because they require large public funds and private hospital for medical care of people who come into direct or indirect contact with these products. The level of knowledge of the operator of the machines for this purpose is essential to minimize these risks by ensuring the quality of spray. This study aimed to determine the level of training of operators in relation to management of pesticides and spraying machines for these inputs in the central region of Rio Grande do Sul. It was observed that the operators have done courses lasting longer than 20 hours, had an education level 50% higher when compared to operators who received courses of less than 20 hours. Operators who participated in courses lasting less than 20 hours, showed a difference of only four percent in respect of operators who have never done any training. The level of training of machine operators for the spraying of pesticides in the Central Region of Rio Grande do Sul, may be considered low in relation to the proper handling of spraying processes.

Periodic inspection on crop sprayers: results according to age of sprayers.

The objectives of the IPP Project--Periodic Inspection on Crop Sprayers--are to develop methods for sprayer certification, analyze quality on spray operation, propose an inspection system for crop sprayers in Brazil, improve environmental quality on spray operation, and reduce costs on chemical control for plant protection systems. Periodic inspections on crop sprayers are performed in several countries and are compulsory in most of them, and it is becoming an important tool for improvement and optimization of use of chemicals. The IPP Project in Brazil is funded by FAPESP--Fundação de Amparo à Pesquisa do Estado de São Paulo. The results so far showed that all the sprayers presented failures. However, most of them could be approved with minor services. As an example, 56.6% of the sprayers with more than 2 years of use presented leaks, 47% of them had damaged hoses and 80.5% presented bad tips (nozzles). These results indicate the need for better procedures of use and maintenance of sprayers, justifying the periodic inspection system.