Displacement Task Research Articles

Predicting Learning: Understanding the Role of Executive Functions in Children's Belief Revision Using Bayesian Models.

Recent studies suggest that learners who are asked to predict the outcome of an event learn more than learners who are asked to evaluate it retrospectively or not at all. One possible explanation for this "prediction boost" is that it helps learners engage metacognitive reasoning skills that may not be spontaneously leveraged, especially for individuals with still-developing executive functions. In this paper, we combined multiple analytic approaches to investigate the potential role of executive functions in elementary school-aged children's science learning. We performed an experiment that investigates children's science learning during a water displacement task where a "prediction boost" had previously been observed-children either made an explicit prediction or evaluated an event post hoc (i.e., postdiction). We then considered the relation of executive function measures and learning, which were collected following the main experiment. Via mixed effects regression models, we found that stronger executive function skills (i.e., stronger inhibition and switching scores) were associated with higher accuracy in Postdiction but not in the Prediction Condition. Using a theory-based Bayesian model, we simulated children's individual performance on the learning task (capturing "belief flexibility"), and compared this "flexibility" to the other measures to understand the relationship between belief revision, executive function, and prediction. Children in the Prediction Condition showed near-ceiling "belief flexibility" scores, which were significantly higher than among children in the Postdiction Condition. We also found a significant correlation between children's executive function measures to our "belief flexibility" parameter, but only for children in the Postdiction Condition. These results indicate that when children provided responses post hoc, they may have required stronger executive function capacities to navigate the learning task. Additionally, these results suggest that the "prediction boost" in children's science learning could be explained by increased metacognitive flexibility in the belief revision process.

Spatiotemporal congruency modulates weighting of visuotactile information in displacement judgments.

Combining or integrating information from multiple senses often provides richer and more reliable estimates for the perception of objects and events. In daily life, sensory information from the same source often is in close spatiotemporal proximity. This can be an important determinant of whether and how multisensory signals are combined. The introduction of advanced technical display systems allows to present multisensory information in virtual environments. However, technical displays can lack the spatiotemporal fidelity of the real world due the rendering delays. Thus, any spatiotemporal incongruency could alter how information is combined. In the current study we tested this by investigating if and how spatially and temporally discrepant tactile displacement cues can supplement imprecise visual displacement cues. Participants performed a visual displacement task with visual and tactile displacement cues under spatial and temporal incongruency conditions. We modelled how participants combined visual and tactile information in visuotactile condition using their performance in visual only condition. We found that temporal incongruency lead to an increase in tactile weights although they were correlated with the congruency condition. In contrast, the spatial incongruency led to individual differences altering cue combination strategies. Our results illustrate the importance of spatiotemporal congruency for combining tactile and visual cues when making visual displacement judgments. Given the altered cue combination strategies and individual differences, we recommend developers to adopt individual spatiotemporal calibration procedures to improve the efficiency of the sensory augmentation.

Pulling the wool over their eyes? Object permanence, numerical competence and categorisation in alternative livestock species

The adaptive abilities of grazing livestock species are not well understood, despite the potential link between behaviour driven decision making and the overall productive efficiency of the animal through foraging strategy. This study aimed to assess and compare these adaptive behaviours, relating to i) object permanence, ii) numerical competence, and iii) categorisation capabilities of domesticated species that possess distinctly different digestive physiologies and backgrounds. Seven animals from each species, including sheep (Ovis aries) (avg. 5 years of age, 60 kg initial weight), goats (Capra hircus) (avg. 3 years, 45 kg initial weight), and alpacas (Lama pacos (Linnaeus, 1758)) (avg. 3 years, 70 kg initial weight), were presented with a total of nine choice tasks, grouped relative to the three abilities being tested (object permanence, numerical competence, and categorisation). Specifically, the stage of object permanence for each subject was tested based on their ability to solve simple visible displacement, to overcome perseveration error, and double invisible displacement tasks. Subjects were also presented with a two-choice task of different open-centre and filled shapes to assess the capacity for simple discrimination and open-ended categorisation. Lastly, numerical competence was compared across five trials consisting of different ratios and volumes of food reward. A basic awareness of object permanence was found in all subjects. Overall, the goats demonstrated the greatest capacity for object permanence across the three species, particularly when presented with more complex three-cup A-not-B tasks. This increase in complexity had no significant effect on goat performance as a group (p = 0.13), whereas alpaca (p = 0.0005) and sheep performance significantly declined (p = 0.04). We also found no evidence to demonstrate contrasting cognitive capabilities between these species in relation to spontaneous numerical cognition (p > 0.05), or in the use of perceptual cues in open-ended categorisation (p = 0.246). This study is the first instance of multiple direct comparisons of cognitive capability across domesticated livestock species. Furthermore, this work is the first account of object permanence, numerical competence and categorisation in alpacas, as well as object permanence in sheep and numerical competence in sheep and goats. This information could prove useful to predict the outcome of interaction between these species in a grazing context and for inferences relating to behaviour driven decision making, such as foraging strategy, and the overall productive efficiency of the animal. Here, we conclude that the three species tested possess comparable capacity for physical cognition in the tasks discussed.

Exendin-4 Prevents Memory Loss and Neuronal Death in Rats with Sporadic Alzheimer-Like Disease.

This study investigated the neuroprotective effects of exendin-4 (EXE-4), an analog of the glucagon-like peptide 1 receptor (GLP-1R) on memory and on the neuronal populations that constitute the hippocampus of rats submitted to a sporadic dementia of Alzheimer's type (SDAT). Male Wistar rats received streptozotocin (STZ icv, 3mg/kg diluted in aCFS, 5µl/ventricle) and were treated for 21days with EXE-4 (10µg/kg, ip; saline as the vehicle). Four groups were formed: vehicle, EXE-4, STZ, and STZ + EXE-4. The groups were submitted to Y-Maze (YM), object recognition (ORT), and object displacement tasks (ODT) to assess learning and memory. The brains were used for immunohistochemical and immunofluorescent techniques with antibodies to NeuN, cleaved caspase-3 (CC3), PCNA, doublecortin (DCX), synaptophysin (SYP), and insulin receptor (IR). STZ worsened spatial memory in the YMT, as well as short-term (STM) and long-term (LTM) memories in the ORT and ODT, respectively. EXE-4 protected against memory impairment in STZ animals. STZ reduced mature neuron density (NeuN) and increased cell apoptosis (CC3) in the DG, CA1, and CA3. EXE-4 protected against neuronal death in all regions. EXE-4 increased PCNA+ cells in all regions of the hippocampus, and STZ attenuated this effect. STZ reduced neurogenesis in DG per se as well as synaptogenesis induced by EXE-4. EXE-4 increased immunoreactivity to IR in the CA1. From these findings, EXE-4 showed a beneficial effect on hippocampal pyramidal and granular neurons in the SDAT showing anti-apoptotic properties and promoting cell proliferation. In parallel, EXE-4 preserved the memory of SDAT rats. EXE-4 appears to enhance synapses at CA3 and DG. In conclusion, these data indicate that agonists to GLP-1R have a beneficial effect on hippocampal neurons in AD.

The role of color in transsaccadic object correspondence.

With each saccade, visual information is disrupted, and the visual system is tasked with establishing object correspondence between the presaccadic and postsaccadic representations of the saccade target. There is substantial evidence that the visual system consults spatiotemporal continuity when determining object correspondence across saccades. The evidence for surface feature continuity, however, is mixed. Surface features that are integral to the saccade target object's identity (e.g., shape and contrast polarity) are informative of object continuity, but features that may only imply the state of the object (e.g., orientation) are ignored. The present study tested whether color information is consulted to determine transsaccadic object continuity. We used two variations of the intrasaccadic target displacement task. In Experiments 1 and 2, participants reported the direction of the target displacement. In Experiments 3 and 4, they instead reported whether they detected any target movement. In all experiments, we manipulated the saccade target's continuity by removing it briefly (i.e., blanking) and by changing its color. We found that large color changes can disrupt stability and increase sensitivity to displacements for both direction and movement reports, although not as strongly as long blank durations (250 ms). Interestingly, even smaller color changes, but not blanking, reduced response biases. These results indicate that disrupting surface feature continuity may impact the process of transsaccadic object correspondence more strongly than spatiotemporal disruptions by both increasing the sensitivity and decreasing the response bias.

Seeing the Error in My "Bayes": A Quantified Degree of Belief Change Correlates with Children's Pupillary Surprise Responses Following Explicit Predictions.

Bayesian models allow us to investigate children's belief revision alongside physiological states, such as "surprise". Recent work finds that pupil dilation (or the "pupillary surprise response") following expectancy violations is predictive of belief revision. How can probabilistic models inform the interpretations of "surprise"? Shannon Information considers the likelihood of an observed event, given prior beliefs, and suggests stronger surprise occurs following unlikely events. In contrast, Kullback-Leibler divergence considers the dissimilarity between prior beliefs and updated beliefs following observations-with greater surprise indicating more change between belief states to accommodate information. To assess these accounts under different learning contexts, we use Bayesian models that compare these computational measures of "surprise" to contexts where children are asked to either predict or evaluate the same evidence during a water displacement task. We find correlations between the computed Kullback-Leibler divergence and the children's pupillometric responses only when the children actively make predictions, and no correlation between Shannon Information and pupillometry. This suggests that when children attend to their beliefs and make predictions, pupillary responses may signal the degree of divergence between a child's current beliefs and the updated, more accommodating beliefs.

New insights into the Haines jump in immiscible two-phase flow displacement

In this study, we develop a numerical model of two-phase flow with a series of different contact angles θ based on real feature structures from scanning electron microscopy. Meanwhile, the interface dynamics during the Haines jump are analyzed based on a typical model of the pore throat system. We found that under different wetting conditions, a series of fluid displacement patterns can be regarded as the minimum pressure drop displacement state for the completion of the constant flow displacement task. Moreover, the Haines jump event is no longer an unfavorable energy event that leads to rapid dissipation of energy but a favorable energy event derived by the system under specific constraints to avoid extra work. These new findings provide new insights into the wettability effect as well as the physical origin of the Haines jump event.

Horses' (Equus caballus) Ability to Solve Visible but Not Invisible Displacement Tasks Is Associated With Frustration Behavior and Heart Rate.

Many frameworks have assessed the ultimate and ontogenetic underpinnings in the development of object permanence, but less is known about whether individual characteristics, such as sex or training level, as well as proximate factors, such as arousal or emotional state, affect performance in these tasks. The current study investigated horses’ performance in visible and invisible displacement tasks and assessed whether specific ontogenetic, behavioral, and physiological factors were associated with performance. The study included 39 Icelandic horses aged 2–25 years, of varying training levels. The horses were exposed to three tasks: (a) a choice test (n = 37), (b) a visible displacement task (n = 35), and (c) an invisible displacement task (n = 31). 27 horses in the choice test, and 8 horses in the visible displacement task, performed significantly better than expected by chance, while none did so in the invisible displacement task. This was also reflected in their group performance, where horses performed above chance level in the choice task and the visible displacement task only. In the invisible displacement task, the group performed significantly worse than expected by chance indicating that horses persistently chose the side where they had last seen the target. None of the individual characteristics included in the study had an effect on performance. Unsuccessful horses had higher heart rate levels, and expressed more behavior indicative of frustration, likely because of their inability to solve the task. The increased frustration/arousal could lead to a negative feedback loop, which might hamper performance in subsequent trials. Care should thus be taken in future experimental designs to closely monitor the arousal level of the tested individuals in order to safeguard comparability.

Ecological Entomology: How Is Gibson's Framework Useful?

Simple SummaryOptic flow can be defined as a vector field of the apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an agent and the scene. In the last century Gibson developed the ecological approach to perception and action in which this optic flow provides an agent (i.e., human, insect, robot) all the information they need to navigate safely in cluttered environments. Gibson’s framework has already proved to be relevant in addressing issues related to the control of human displacement and by offering the robotics community a framework for carrying out new generations of studies. We would like to argue in this contribution that the ecological approach to perception and action, taken as a whole, provides powerful theoretical and methodological tools allowing the entomologist community to: (i) take a critical look at the research carried out to date, (ii) develop new experimental protocols, and (iii) raise new questions beyond the scope of current investigations. After a concise literature review about the perceptual control of displacement in insects, we will present the framework proposed by Gibson and suggest its added value for carrying out research in the field of entomology.To date, numerous studies have demonstrated the fundamental role played by optic flow in the control of goal-directed displacement tasks in insects. Optic flow was first introduced by Gibson as part of their ecological approach to perception and action. While this theoretical approach (as a whole) has been demonstrated to be particularly suitable for the study of goal-directed displacements in humans, its usefulness in carrying out entomological field studies remains to be established. In this review we would like to demonstrate that the ecological approach to perception and action could be relevant for the entomologist community in their future investigations. This approach could provide a conceptual and methodological framework for the community in order to: (i) take a critical look at the research carried out to date, (ii) develop rigorous and innovative experimental protocols, and (iii) define scientific issues that push the boundaries of the current scientific field. After a concise literature review about the perceptual control of displacement in insects, we will present the framework proposed by Gibson and suggest its added value for carrying out research in the field of behavioral ecology in insects.

Exercise alters LPS-induced glial activation in the mouse brain.

Experimental and epidemiological evidence suggest that modifiable lifestyle factors, including physical exercise, can build structural and cognitive reserve in the brain, increasing resilience to injury and insult. Accordingly, exercise can reduce the increased expression of proinflammatory cytokines in the brain associated with ageing or experimentally induced neuroinflammation. However, the cellular mechanisms by which exercise exerts this effect are unknown, including the effects of exercise on classic or alternative activation of astrocytes and microglia. In the present study, we assess the effects of nine consecutive days of treadmill running on the glial cell response to a single systemic injection of lipopolysaccharide (LPS) and, in parallel, the effects on spatial learning and memory. We show that prior exercise protects against LPS-induced impairment of performance in the object displacement task concomitant with attenuation of IL-1β, TNFα and IL-10 mRNA expression in the hippocampus. Assessment of isolated astrocytes and microglia revealed that LPS induced a proinflammatory response in these cells that was not observed in cells prepared from the brains of mice who had undergone prior exercise. The results suggest that exercise modulates neuroinflammation by reducing the proinflammatory microglial response, suggesting a mechanism by which exercise may be neuroprotective.

The Risk Assessment of Low Back Pain Based on Allowable Weight Limits for Manual Lifting in Iranian Women Workers

Background: Manual load lifting is one of the most important risk factors for musculoskeletal disorders, including occupational low back pain. These disorders are common in women workers who perform manual load lifting and displacement tasks at the workplace. Objectives: To determine the level of musculoskeletal disorders and to evaluate the recommended limits of manual load lifting in women workers using WISHA checklist and ACGIH TLV, the recommended limits of Iran, and compare the results of two methods. Methods: This cross-sectional study was conducted on 100 women workers who performed manual loading tasks in 2018. Nordic questionnaire was used to determine the prevalence of musculoskeletal disorders, and two methods, WISHA checklist and ACGIH TLV, were used to determine the recommended allowable limits for manual load lifting. Results: The results of the prevalence assessment of musculoskeletal disorders showed that most of the musculoskeletal disorders were in the low back (55%) in the past 12 months. The results of the assessment of the allowable lifting limits also showed that 8% of women in the WISHA checklist method and 31% in the ACGIH TLV method were at risk for low back injuries. The kappa coefficient test (0.031) also showed that there is a poor and insignificant agreement between the two methods of WISHA checklist and ACGIH TLV in determining the allowable limits for manual lifting. Conclusions: The results of this study showed a poor agreement between the WISHA checklist and ACGIH TLV in determining the allowable limits for manual lifting, which suggest that the two methods are not mutually exclusive. Hence, owing to the increasing presence of women in various occupations and raising the hand load-lifting and, naturally increasing occupational low back pain among them, it is necessary that in a comprehensive study, the allowable limits of lifting loads according to anthropometric and physiological characteristics of Iranian women, prepare and compile according to a comprehensive instruction.

Intra-saccadic displacement sensitivity after a lesion to the posterior parietal cortex

Visual perception is introspectively stable and continuous across eye movements. It has been hypothesized that displacements in retinal input caused by eye movements can be dissociated from displacements in the external world using extra-retinal information, such as a corollary discharge from the oculomotor system. The extra-retinal information can inform the visual system about an upcoming eye movement and accompanying displacements in retinal input. The parietal cortex has been hypothesized to be critically involved in integrating retinal and extra-retinal information. Two tasks have been widely used to assess the quality of this integration: double-step saccades and intra-saccadic displacements. Double-step saccades performed by patients with parietal cortex lesions seemed to show hypometric second saccades. However, recently idea has been refuted by demonstrating that patients with very similar lesions were able to perform the double step saccades, albeit taking multiple saccades to reach the saccade target. So, it seems that extra-retinal information is still available for saccade execution after a lesion to the parietal lobe. Here, we investigated whether extra-retinal signals are also available for perceptual judgements in nine patients with strokes affecting the posterior parietal cortex. We assessed perceptual continuity with the intra-saccadic displacement task. We exploited the increased sensitivity when a small temporal blank is introduced after saccade offset (blank effect). The blank effect is thought to reflect the availability of extra-retinal signals for perceptual judgements. Although patients exhibited a relative difference to control subjects, they still demonstrated the blank effect. The data suggest that a lesion to the posterior parietal cortex (PPC) alters the processing of extra-retinal signals but does not abolish their influence altogether.

El papel de la experiencia visual previa en el desarrollo de habilidades de permanencia de objetos en delfines nariz de botella (Tursiops truncatus)

La permanencia de los objetos, la capacidad de representar objetos ocultos, no se ha evaluado ampliamente en los cetáceos y la evidencia disponible es contradictoria. Aunque se cree que los delfines nariz de botella (Tursiops truncatus) están dotados de las capacidades cognitivas necesarias para aprobar pruebas complejas de permanencia de objetos, han fallado en una serie de tareas que involucran desplazamientos invisibles, lo que plantea la cuestión de si logran la permanencia de los objetos maestros. La falta de comprensión de la contención o la falta de experiencia en el seguimiento de objetos ocultos tanto de la vista como de la ecolocación pueden explicar estos resultados inesperados. El objetivo del presente estudio fue probar estas dos hipótesis en una serie de tareas de desplazamiento visibles e invisibles con delfines nariz de botella. Nuestros resultados sugieren que los delfines pueden tener éxito en tareas complejas de permanencia de objetos, pero solo si tienen experiencia visual previa con los movimientos de objetos dentro de otros objetos. Por lo tanto, estos resultados apuntan a un papel importante de la experiencia visual en el desarrollo de habilidades de permanencia de objetos.

Representational momentum in displacement tasks: Relative object weight matters in toddlers’ search behavior

Various developmental studies have demonstrated that implied object weight is a key variable in children’s interpretations of motion, such as predicting the objects’ speeds. An additional bias in predictions of object motion is representational momentum (RM), where objects are anticipated to be found in a location farther along in the direction of motion from where they actually are. The present study aimed to evaluate when children begin to be sensitive to relative weight in a RM-related search task. Toddlers (N = 60) aged 2, 2½ and 3 years first visually and manually experienced a heavy ball, a light ball, or both balls at the same time. They then watched one of the balls roll down a ramp and behind a screen with four doors, with a visible barrier placed along the ramp in various positions that would stop the ball’s motion, after which the toddlers were allowed to search for the ball by opening one of the doors. Search accuracy generally increased with age but the accuracy also depended on condition. Relative heaviness in particular led to reduced search accuracy. Further analyses revealed relative heaviness to lead to more searches farther beyond the barrier, adding to the expected RM effect.

Visual working memory supports perceptual stability across saccadic eye movements.

Vision is suppressed during saccadic eye movements. To create a stable perception of the visual world we must compensate for the gaps in visual input caused by this suppression. Some theories of perceptual stability, such as the Saccade Target Object Theory (McConkie & Currie, 1996), propose that stability relies on object correspondence across saccades. According to these views, the visual system encodes features of the saccade target into visual working memory (VWM) before a saccade is made. After the saccade, participants attempt to locate those features within a small region near the fovea. If this locating process succeeds, perceptual stability is maintained. The present study investigated directly whether perceptual stability relies on VWM. If it does, perceived stability should be impaired when VWM is loaded with other visual information. Participants detected saccade target displacements while simultaneously maintaining a VWM or verbal working memory (AWM) load. In three experiments, a VWM load negatively impacted participants' ability to detect saccade target displacements and the saccade target displacement task negatively impacted memory for VWM task items. Neither of these effects were apparent when AWM was loaded, suggesting that performance on VWM and saccade target displacement detection tasks, and thus perceptual stability, relies on VWM resources. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Topology optimization of leaf flexures to maximize in-plane to out-of-plane compliance ratio

In fields requiring precision manipulation, monolithic flexures are frequently used to guide motion. They utilize the structure's predictable elastic deformation, when a force is applied, to facilitate linear and rotational motions. Amongst the several common flexure designs, leaf flexures are the best suited to ‘large’ displacement tasks. Their range is typically restricted by the actuator's supplied force, such that reducing stiffness in the motion direction beneficially increases displacement. However, high out-of-plane stiffness is required to support structural loads and reject parasitic motions. In this work, topology optimization is investigated to maximize the in-plane to out-of-plane compliance ratio of a leaf flexure. The minimization of out-of-plane compliance in leaf flexures is also investigated for comparison. In both cases, the optimized structures resemble trusses. Compliance ratio optimized structures offer performance 1.5 to 6 times greater than standard leaf structures, with reduced mass. From the results, a parameterized flexure design is suggested, which can replace leaf flexures in 3D printed mechanisms. A parallelogram linear flexure guide is analyzed as an example of a practical implementation of the optimized design.

TMS over posterior parietal cortex disrupts trans-saccadic visual stability

BackgroundSaccadic eye movements change the retinal location of visual objects, but we do not experience the visual world as constantly moving, we perceive it as seamless and stable. This visual stability may be achieved by an internal or efference copy of each saccade that, combined with the retinal information, allows the visual system to cancel out or ignore the self-caused retinal motion. ObjectiveThe current study investigated the underlying brain mechanisms responsible for visual stability in humans with online transcranial magnetic stimulation (TMS). MethodsWe used two classic tasks that measure efference copy: the double-step task and the in-flight displacement task. The double-step task requires subjects to make two memory-guided saccades, the second of which depends on an accurate internal copy of the first. The in-flight displacement task requires subjects to report the relative location of a (possibly displaced) target across a saccade. In separate experimental sessions, subjects participated in each task while we delivered online 3-pulse TMS over frontal eye fields (FEF), posterior parietal cortex, or vertex. TMS was contingent on saccade execution. ResultsSecond saccades were not disrupted in the double-step task, but surprisingly, TMS over FEF modified the metrics of the ongoing saccade. Spatiotopic performance in the in-flight displacement task was altered following TMS over parietal cortex, but not FEF or vertex. ConclusionThese results suggest that TMS disrupted eye-centered position coding in the parietal cortex. Trans-saccadic correspondence, and visual stability, may therefore causally depend on parietal maps.

Spatial transposition tasks in Indian sloth bears (Melursus ursinus) and Bornean sun bears (Helarctos malayanus euryspilus).

Spatial transposition tasks assess individuals' ability to represent nonvisible spatial object displacements. Several nonhuman mammal species have been tested on this task including primates, cats, and dogs, but to date, great apes seem the only taxon that has repeatedly and consistently solved spatial transposition tasks. The authors investigated the ability of captive sloth and sun bears to solve spatial transposition tasks. Both species belong to the same taxonomic group as cats and dogs, but unlike them and similar to apes, they have an omnivorous diet that requires them to keep track of fruit sources in space and time. The bears were first tested on a visible displacement task and those that succeeded were further tested on a spatial transposition task that involved a 180° transposition, followed by 2 tasks with two 360° transpositions. All 7 sloth bears and 7 out of 9 sun bears solved the visible displacement task. The 180° transposition task was solved by 6 out of 7 sloth bears and 1 out of the 5 tested sun bears. Three sloth bears were tested on all 4 experiments and even solved 2-chained 360° transpositions. Control conditions were conducted showing that the bears' performance did not rely on olfactory or auditory cues. The results provide the first indication that bears might be able to track invisible objects. Further studies will be necessary to confirm these results and to control the influence of associative learning. The present study emphasizes the importance of including different animal species in the investigation of what underlies the evolution of different cognitive skills. (PsycINFO Database Record

What do monkeys know about others’ knowledge?

Recently, comparative psychologists have suggested that primates represent others’ knowledge states. Evidence for this claim comes from studies demonstrating that primates expect others to maintain representations of objects when those objects are not currently visible. However, little work has explored whether nonhuman primates expect others to share the more sophisticated kinds of object knowledge that they themselves possess. We therefore investigated whether primates attribute to others knowledge that is acquired through the mental transformation of a static object representation. Specifically, we tested whether rhesus macaques (Macaca mulatta) expected a human demonstrator to solve a difficult rotational displacement task. In Experiment 1, monkeys watched a demonstrator hide a piece of fruit in one of two boxes. The monkey and the demonstrator then watched the boxes rotate 180°. We found that monkeys looked longer when the demonstrator reached into the box that did not contain the fruit, indicating that they expected her to be able to track the fruit to its current location. In Experiment 2, we ruled out the possibility that monkeys simply expected the demonstrator to search for the food in its true location. When the demonstrator did not witness the rotation event, monkeys looked equally long at the two reaching outcomes. These results are consistent with the interpretation that rhesus macaques expect others to dynamically update their representations of unseen objects.

Reliability of the rating of perceived exertion (Borg Scale) in post-stroke during 2 tasks of daily life

The rating of perceived exertion (RPE) scales are used to quantify and prescribe an intensity of exercise and physical activity. Its use in stroke is widespread but its reliability can be questioned by multiple problems inherent to stroke such as cognitive disorders. The objective was to evaluate the reliability of RPE by the BORG scale (6–20) on a task of displacement and climbing/descending stairs in a population of stroke survivors. All subjects with a history of stroke followed in the PMR department of the Limoges University Hospital were recruited. Subjects with cognitive impairments not permitting the use of the Borg scale were excluded. Participants were required to perform a 6-minute of displacement (6MD) at their self-comfort speed, with their usual mode of ambulation, and for the subjects in capacity, a climb and descent of a staircase. The total energy expenditure (TEE) was measured by a portable respiratory gas analyzer (Metamax3B). The RPE was assessed at the end of the tasks by the Borg scale (6–20). A correlation analysis was performed between the TEE values and RPE. Forty-six subjects aged 65.2 years (± 13.7) were included. The TEE/min averaged 5.6 kcal/min (DS = 1.2 kcal/min) for the displacement task and 9.58 kcal/min (DS = 4.3 kcal/min) for the descent stairs. The RPE averaged 10.6 (min 6–max 15) for the 6MD and 11.1 (min 6–max 16) for the task of stairs. No correlation was found between the BORG and the TEE/min, whether for the task of D6M or stairs (r6MD = −0.03, P = 0.8, rstairs = −0.02, P = 0.7). In addition, there was no significant variation between the RPE of 6MD and that of the stairs, while TEE/min showed a 70% increase between displacement and stairs ( P < 0.001). Despite varying levels of effort intensity, no correlation was found between RPE and the TEE on a task of walking and a task of climbing and descending the stairs in a cohort of stoke survivors.