The National Football League-225 Bench Press Test and the Size-Weight Illusion

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.The purpose of this study was to test reports that size and arrangement manipulations of weight plates (i.e., inducing a size-weight illusion [SWI]) would have an effect on athletic weightlifting performance. The participants were 72 experienced, weight-trained collegiate American football players. Across 3 weeks, each athlete performed three different repetitions-to-fatigue bench press tests (NFL-225, SWI-225, and SWI-215). A multiple regression revealed a positive association between participants' strength relative to the test load and repetitions for NFL-225 and SWI-215, but no association with SWI-225. To explore these results, players were ranked into quartiles based on their one-repetition maximum relative to 102.27 kg (225 lb), and a 3 × 4 repeated measures analysis of variance was conducted. The primary finding was a significant Test Condition × Quartile interaction ( p = .004). Bonferroni-corrected pairwise comparisons revealed that Quartile 4 (those with lowest strength relative to test load) completed more repetitions for SWI-225 compared with NFL-225 ( p = .049). These results suggest that alternate weight plate arrangements may be beneficial for those whose bench press load is near the lifter's one-repetition maximum. However, variations of the SWI do not appear to affect the performance of repetitions-to-fatigue bench press tests for the majority of collegiate American football players

Toward "Pseudo-Haptic Avatars": Modifying the Visual Animation of Self-Avatar Can Simulate the Perception of Weight Lifting

International audienceIn this paper we study how the visual animation of a self-avatar can be artificially modified in real-time in order to generate different haptic perceptions. In our experimental setup, participants could watch their self-avatar in a virtual environment in mirror mode while performing a weight lifting task. Users could map their gestures on the self-animated avatar in real-time using a Kinect. We introduce three kinds of modification of the visual animation of the self-avatar according to the effort delivered by the virtual avatar: 1) changes on the spatial mapping between the user's gestures and the avatar, 2) different motion profiles of the animation, and 3) changes in the posture of the avatar (upper-body inclination). The experimental task consisted of a weight lifting task in which participants had to order four virtual dumbbells according to their virtual weight. The user had to lift each virtual dumbbells by means of a tangible stick, the animation of the avatar was modulated according to the virtual weight of the dumbbell. The results showed that the altering the spatial mapping delivered the best performance. Nevertheless, participants globally appreciated all the different visual effects. Our results pave the way to the exploitation of such novel techniques in various VR applications such as sport training, exercise games, or industrial training scenarios in single or collaborative mode

A System to Monitor Cognitive Workload in Naturalistic High-Motion Environments

Across many careers, individuals face alternating periods of high and low attention and cognitive workload can impair cognitive function and undermine job performance. We have designed and are developing an unobtrusive system to Monitor, Extract, and Decode Indicators of Cognitive Workload (MEDIC) in naturalistic, high-motion environments. MEDIC is designed to warn individuals, teammates, or supervisors when steps should be taken to augment cognitive readiness. We first designed and manufactured a forehead sensor device that includes a custom fNIRS sensor and a three-axis accelerometer designed to be mounted on the inside of a baseball cap or headband, or standard issue gear such as a helmet or surgeon’s cap. Because the conditions under which MEDIC is designed to operate are more strenuous than typical research efforts assessing cognitive workload, motion artifacts in our data were a persistent issue. Results show wavelet-based filtering improved data quality to salvage data from even the highest-motion conditions. MARA spline motion correction did not further improve data quality. Our testing shows that each of the methods is extremely effective in reducing the effects of motion transients present in the data. In combination, they are able to almost completely remove the transients in the signal while preserving cardiac and low frequency information in the signal which was previously unrecoverable. This has substantially improved the stability of the physiological measures produced by the sensors in high noise conditions

The material-weight illusion disappears or inverts in objects made of two materials

© the American Physiological Society. The material-weight illusion disappears or inverts in objects made of two materials. J Neurophysiol 121: 996 –1010, 2019. First published January 23, 2019; doi:10.1152/jn.00199.2018.—The material-weight illusion (MWI) occurs when an object that looks heavy (e.g., stone) and one that looks light (e.g., Styrofoam) have the same mass. When such stimuli are lifted, the heavier-looking object feels lighter than the lighter-looking object, presumably because well-learned priors about the density of different materials are violated. We examined whether a similar illusion occurs when a certain weight distribution is expected (such as the metal end of a hammer being heavier), but weight is uniformly distributed. In experiment 1, participants lifted bipartite objects that appeared to be made of two materials (combinations of stone, Styrofoam, and wood) but were manipulated to have a uniform weight distribution. Most participants experienced an inverted MWI (i.e., the heavier-looking side felt heavier), suggesting an integration of incoming sensory information with density priors. However, a replication of the classic MWI was found when the objects appeared to be uniformly made of just one of the materials (experiment 2). Both illusions seemed to be independent of the forces used when the objects were lifted. When lifting bipartite objects but asked to judge the weight of the whole object, participants experienced no illusion (experiment 3). In experiment 4, we investigated weight perception in objects with a nonuniform weight distribution and again found evidence for an integration of prior and sensory information. Taken together, our seemingly contradictory results challenge most theories about the MWI. However, Bayesian integration of competing density priors with the likelihood of incoming sensory information may explain the opposing illusions. NEW & NOTEWORTHY We report a novel weight illusion that contradicts all current explanations of the material-weight illusion: When lifting an object composed of two materials, the heavier-looking side feels heavier, even when the true weight distribution is uniform. The opposite (classic) illusion is found when the same materials are lifted in two separate objects. Identifying the common mechanism underlying both illusions will have implications for perception more generally. A potential candidate is Bayesian inference with competing priors

Cross-sensory correspondences:heaviness is dark and low-pitched

Everyday language reveals how stimuli encoded in one sensory feature domain can possess qualities normally associated with a different domain (e.g., higher pitch sounds are bright, light in weight, sharp, and thin). Such cross-sensory associations appear to reflect crosstalk among aligned (corresponding) feature dimensions, including brightness, heaviness, and sharpness. Evidence for heaviness being one such dimension is very limited, with heaviness appearing primarily as a verbal associate of other feature contrasts (e.g., darker objects and lower pitch sounds are heavier than their opposites). Given the presumed bi-directionality of the crosstalk between corresponding dimensions, heaviness should itself induce the cross-sensory associations observed elsewhere, including with brightness and pitch. Taking care to dissociate effects arising from the size and mass of an object this is confirmed. When hidden objects varying independently in size and mass are lifted, objects that feel heavier are judged to be darker and to make lower pitch sounds than objects feeling less heavy. These judgements track the changes in perceived heaviness induced by the size-weight illusion. The potential involvement of language, natural scene statistics, and Bayesian processes in correspondences, and the effects they induce, is considered

MindFull: Tableware to Manipulate Sensory Perception and Reduce Portion Sizes

Rising obesity levels across the world are a major threat to health, well-being and the economy. Reducing the amount we eat is difficult. This is partly because consciously controlling our eating typically increases the amount we eat. The paper presents the MindFull tableware—a new design for tableware to help people to reduce portion sizes effectively and unconsciously. MindFull designs exploit a range of features of our sensory perception identified from psychological research literature. Initial experiments show encouraging results for the design and suggest several directions for future development, research and applications for the design findings

Material perception and action : The role of material properties in object handling

This dissertation is about visual perception of material properties and their role in preparation for object handling. Usually before an object is touched or picked-up we estimate its size and shape based on visual features to plan the grip size of our hand. After we have touched the object, the grip size is adjusted according to the provided haptic feedback and the object is handled safely. Similarly, we anticipate the required grip force to handle the object without slippage, based on its visual features and prior experience with similar objects. Previous studies on object handling have mostly examined object characteristics that are typical for object recognition, e.g., size, shape, weight, but in the recent years there has been a growing interest in object characteristics that are more typical to the type of material the object is made from. That said, in a series of studies we investigated the role of perceived material properties in decision-making and object handling, in which both digitally rendered materials and real objects made of different types of materials were presented to human subjects and a humanoid robot. Paper I is a reach-to-grasp study where human subjects were examined using motion capture technology. In this study, participants grasped and lifted paper cups that varied in appearance (i.e., matte vs. glossy) and weight. Here we were interested in both the temporal and spatial components of prehension to examine the role of material properties in grip preparation, and how visual features contribute to inferred hardness before haptic feedback has become available. We found the temporal and spatial components were not exclusively governed by the expected weight of the paper cups, instead glossiness and expected hardness has a significant role as well. In paper II, which is a follow-up on Paper I, we investigated the grip force component of prehension using the same experimental stimuli as used in paper I. In a similar experimental set up, using force sensors we examined the early grip force magnitudes applied by human subjects when grasping and lifting the same paper cups as used in Paper I. Here we found that early grip force scaling was not only guided by the object weight, but the visual characteristics of the material (i.e., matte vs. glossy) had a role as well. Moreover, the results suggest that grip force scaling during the initial object lifts is guided by expected hardness that is to some extend based on visual material properties. Paper III is a visual judgment task where psychophysical measurements were used to examine how the material properties, roughness and glossiness, influence perceived bounce height and consequently perceived hardness. In a paired-comparison task, human subjects observed a bouncing ball bounce on various surface planes and judged their bounce height. Here we investigated, what combination of surface properties, i.e., roughness or glossiness, makes a surface plane to be perceived bounceable. The results demonstrate that surface planes with rough properties are believed to afford higher bounce heights for the bouncing ball, compared to surface planes with smooth properties. Interestingly, adding shiny properties to the rough and smooth surface planes, reduced the judged difference, as if surface planes with gloss are believed to afford higher bounce heights irrespective of how smooth or rough the surface plane is beneath. This suggests that perceived bounce height involves not only the physical elements of the bounce height, but also the visual characteristics of the material properties of the surface planes the ball bounces on. In paper IV we investigated the development of material knowledge using a robotic system. A humanoid robot explored real objects made of different types of materials, using both camera and haptic systems. The objects varied in visual appearances (e.g., texture, color, shape, size), weight, and hardness, and in two experiments, the robot picked up and placed the experimental objects several times using its arm. Here we used the haptic signals from the servos controlling the arm and the shoulder of the robot, to obtain measurements of the weight and hardness of the objects, and the camera system to collect data on the visual features of the objects. After the robot had repeatedly explored the objects, an associative learning model was created based on the training data to demonstrate how the robotic system could produce multi-modal mapping between the visual and haptic features of the objects. In sum, in this thesis we show that visual material properties and prior knowledge of how materials look like and behave like has a significant role in action planning

Sensorimotor Differences in Autism Spectrum Disorder: An evaluation of potential mechanisms.

This thesis examined the aetiology of sensorimotor impairments in Autism Spectrum Disorder: a neurodevelopmental condition that affects an individual’s socio-behavioural preferences, personal independence, and quality of life. Issues relating to clumsiness and movement coordination are common features of autism that contribute to wide-ranging daily living difficulties. However, these characteristics are relatively understudied and there is an absence of evidence-based practical interventions. To pave the way for new, scientifically-focused programmes, a series of studies investigated the mechanistic underpinnings of sensorimotor differences in autism. Following a targeted review of previous research, study one explored links between autistic-like traits and numerous conceptually-significant movement control functions. Eye-tracking analyses were integrated with force transducers and motion capture technology to examine how participants interacted with uncertain lifting objects. Upon identifying a link between autistic-like traits and context-sensitive predictive action control, study two replicated these procedures with a sample of clinically-diagnosed participants. Results illustrated that autistic people are able to use predictions to guide object interactions, but that uncertainty-related adjustments in sensorimotor integration are atypical. Such findings were advanced within a novel virtual-reality paradigm in study three, which systematically manipulated environmental uncertainty during naturalistic interception actions. Here, data supported proposals that precision weighting functions are aberrant in autistic people, and suggested that these individuals have difficulties with processing volatile sensory information. These difficulties were not alleviated by the experimental provision of explicit contextual cues in study four. Together, these studies implicate the role of implicit neuromodulatory mechanisms that regulate dynamic sensorimotor behaviours. Results support the development of evidence-based programmes that ‘make the world more predictable’ for autistic people, with various theoretical and practical implications presented. Possible applications of these findings are discussed in relation to recent multi-disciplinary research and conceptual advances in the field, which could help improve daily living skills and functional quality of life.Economic and Social Research Council (ESRC

Does gesture strengthen sensorimotor knowledge of objects? The case of the size-weight illusion

Co-speech gestures have been proposed to strengthen sensorimotor knowledge related to objects’ weight and manipulability. This pre-registered study (https://www.osf.io/9uh6q/) was designed to explore how gestures affect memory for sensorimotor information through the application of the visual-haptic size-weight illusion (i.e., objects weigh the same, but are experienced as different in weight). With this paradigm, a discrepancy can be induced between participants’ conscious illusory perception of objects’ weight and their implicit sensorimotor knowledge (i.e., veridical motor coordination). Depending on whether gestures reflect and strengthen either of these types of knowledge, gestures may respectively decrease or increase the magnitude of the size-weight illusion. Participants (N = 159) practiced a problem-solving task with small and large objects that were designed to induce a size-weight illusion, and then explained the task with or without co-speech gesture or completed a control task. Afterwards, participants judged the heaviness of objects from memory and then while holding them. Confirmatory analyses revealed an inverted size-weight illusion based on heaviness judgments from memory and we found gesturing did not affect judgments. However, exploratory analyses showed reliable correlations between participants’ heaviness judgments from memory and (a) the number of gestures produced that simulated actions, and (b) the kinematics of the lifting phases of those gestures. These findings suggest that gestures emerge as sensorimotor imaginings that are governed by the agent’s conscious renderings about the actions they describe, rather than implicit motor routines

Torque-planning errors affect the perception of object properties and sensorimotor memories during object manipulation in uncertain grasp situations.

This is the author accepted manuscript. The final version is available from American Physiological Society via the DOI in this record.Predicting instead of only reacting to the properties of objects we grasp is crucial to dexterous object manipulation. Although we normally plan our grasps according to well-learned associations, we rely on implicit sensorimotor memories when we learn to interact with novel or ambiguous objects. However, little is known about the influence of sensorimotor predictions on subsequent perception and action. Here, young and elderly subjects repeatedly lifted an object in which the center of mass (CoM) was randomly varied between trials straight upward with the aim of preventing object tilts. After each lift, subjects indicated the location of the perceived CoM and reported how heavy the object felt. Surprisingly, we found that sensorimotor torque memories eventually causing initial lifting errors had substantial effects on the perception of torques, weight, and the torque planning for the next lift. Whereas subjects tended to partly retain their previous erroneous sensorimotor memories (instead of solely relying on the previously encountered torque for the upcoming motor plan), they perceived encountered torques to be stronger when they erroneously predicted them. Additionally, we found that torque prediction errors, as well as the actual torques, made the object feel heavier. By contrast, perception did not influence upcoming motor control. There were no major differences observed between the age groups. The sensorimotor impact on torque perception can be explained by internal feedforward prediction highlighting task-relevant errors, while the partial retention and adaptation of sensorimotor torque memories is reconciled with the trial-to-trial learning rule for motor adaptation. NEW & NOTEWORTHY The current study is the first to demonstrate in an object manipulation task in uncertainty that errors in the sensorimotor prediction of torques influence the perception of both torques and weight, whereas sensorimotor torque memories are partly retained and partly adapted to planning errors. Our results provide novel insights into the predictive mechanisms underpinning the common everyday task of object manipulation and further support theories about the predictive modulation of perception established in other neuroscientific disciplines