The Size-Weight Illusion Is Not an Illusion When Picking the Best Objects to Throw

Heaviness perception involves a misperception of weight known, since the 19th century, as the Size-Weight Illusion ^1^. The larger of two objects of equal mass is reported to be lighter than the smaller when they are lifted. The illusion has been found to be reliable and robust. It persists even when people know that the masses are equal and handle objects properly ^2^. It has been exhibited by children of only 2 years of age ^3,4^. All this suggests that the effect might be intrinsic to humans. Although different hypotheses have been advanced to account for the illusion over the 100+ years it has been studied ^5-11^, its origin remains unknown. More recently, people's perception of optimal objects for long distance throwing was found to exhibit a size-weight relation similar to the illusion ^12,13^, greater weights were picked for larger objects and they were indeed thrown to the greatest distances. Here we show that the perception of heaviness (including the illusion) and perception of optimal objects for long distance throwing are in fact equivalent. Thus, the size-weight illusion has a useful application: optimal objects for throwing are picked by a thrower as having a particular heaviness, which is the best heaviness learned when learning to throw ^14,15^. Long distance throwing is a uniquely human ability that is understood to have enabled our species to survive and even thrive during the ice ages ^16-22^. The fact that the illusion is a functional component of human throwing skill adds credence to the idea that it is intrinsic to the species

Identifying the information for the visual perception of relative phase

The production and perception of coordinated rhythmic movement are very specifically structured. For production and perception, 0° mean relative phase is stable, 180° is less stable, and no other state is stable without training. It has been hypothesized that perceptual stability characteristics underpin the movement stability characteristics, which has led to the development of a phase-driven oscillator model (e.g., Bingham, 2004a, 2004b). In the present study, a novel perturbation method was used to explore the identity of the perceptual information being used in rhythmic movement tasks. In the three conditions, relative position, relative speed, and frequency (variables motivated by the model) were selectively perturbed. Ten participants performed a judgment task to identify 0° or 180° under these perturbation conditions, and 8 participants who had been trained to visually discriminate 90° performed the task with perturbed 90° displays. Discrimination of 0° and 180° was unperturbed in 7 out of the 10 participants, but discrimination of 90° was completely disrupted by the position perturbation and was made noisy by the frequency perturbation. We concluded that (1) the information used by most observers to perceive relative phase at 0° and 180° was relative direction and (2) becoming an expert perceiver of 90° entails learning a new variable composed of position and speed

Proprioceptive perception of phase variability

Previous work has established that judgments of relative phase variability of 2 visually presented oscillators covary with mean relative phase. Ninety degrees is judged to be more variable than 0° or 180°, independently of the actual level of phase variability. Judged levels of variability also increase at 180°. This pattern of judgments matches the pattern of movement coordination results. Here, participants judged the phase variability of their own finger movements, which they generated by actively tracking a manipulandum moving at 0°, 90°, or 180°, and with 1 of 4 levels of Phase Variability. Judgments covaried as an inverted U-shaped function of mean relative phase. With an increase in frequency, 180° was judged more variable whereas 0° was not. Higher frequency also reduced discrimination of the levels of Phase Variability. This matching of the proprioceptive and visual results, and of both to movement results, supports the hypothesized role of online perception in the coupling of limb movements. Differences in the 2 cases are discussed as due primarily to the different sensitivities of the systems to the information

Object recognition using metric shape

AbstractMost previous studies of 3D shape perception have shown a general inability to visually perceive metric shape. In line with this, studies of object recognition have shown that only qualitative differences, not quantitative or metric ones can be used effectively for object recognition. Recently, Bingham and Lind (2008) found that large perspective changes (⩾45°) allow perception of metric shape and Lee and Bingham (2010) found that this, in turn, allowed accurate feedforward reaches-to-grasp objects varying in metric shape. We now investigated whether this information would allow accurate and effective recognition of objects that vary in respect to metric shape. Both judgment accuracies (d′) and reaction times confirmed that, with the availability of visual information in large perspective changes, recognition of objects using quantitative as compared to qualitative properties was equivalent in accuracy and speed of judgments. The ability to recognize objects based on their metric shape is, therefore, a function of the availability or unavailability of requisite visual information. These issues and results are discussed in the context of the Two Visual System hypothesis of Milner and Goodale (1995, 2006)

Perceiving Size in Events Via Kinematic Form

Traditional solutions to the problem of size perception have confounded size and distance perception. We investigated size perception using information that is independent of distance. As do the shapes of biological objects (Bingham, 1992), the forms of events vary with size. We investigated whether observers were able to use size specific variations in the kinematic forms of events as information about size. Observers judged the size of a ball in displays containing only kinematic information about size. This was accomplished by covarying object distance and actual size to produce equivalent image sizes for all objects and extents in the displays. Simulations were generated using dynamical models for planar events. Motions were confined to a plane parallel to the display screen. Mass density, friction, and elasticity were held constant over changes in size, simulating wooden balls. Observers were able to detect the increasing sizes of the equal image size balls. Mean size judgments exhibited a pattern predicted by a scaling factor in the equation of motion derived using similarity analysis

"Adaptation" to Displacement Prisms Is Sensorimotor Learning

Observers reaching to a target seen through wedge shaped displacement prisms initially reach in the direction of displacement, correcting their reaches over a series of about 12 trials. With subsequent removal of the prisms, observers initially reach to the opposite side of the target, correcting over about 6 trials. This phenomenon has been called "adaptation" because of its similarity to the adaptation of sensory thresholds to prevailing energy levels. W e show, however, that this perturbation to visually guided reaching only mimics sensory adaptation initially. Subsequent changes show that this is sensorimotor learning. Error in pointing to targets is the commonly used measure. W e measured times for rapid reaches to place a stylus in a target. Participants wearing a prism worked to achieve criterion times previously established with normal, unperturbed vision. Blocks of trials with and without a prism were alternated. Both the number of trials to criterion and the mean times per block of trials decreased over successive blocks in a session, as well as over successive days. By the third day, participants were able to respond rapidly to perturbations. This reflects the acquisition of a new skill that must be similar to that acquired by users of corrective lens

Is hefting to perceive affordances for throwing is a smart perceptual mechanism

found that, by hefting objects of different sizes and weights, people could choose the optimal weight in each size for throwing to a maximum distance. In Experiment 1, the authors replicated this result. G. P. Bingham et al. hypothesized that hefting is a smart mechanism that allows objects to be perceived in the context of throwing dynamics. This hypothesis entails 2 assumptions. First, hefting by hand is required for information about throwing by hand. The authors tested and confirmed this in Experiments 2 and 3. Second, optimal objects are determined by the dynamics of throwing. In Experiment 4, the authors tested this by measuring throwing release angles and using them with mean thrown distances from Experiment 1 and object sizes and weights to simulate projectile motion and recover release velocities. The results showed that only weight, not size, affects throwing. This failed to provide evidence supporting the particular smart mechanism hypothesis of G. P. Bingham et al. Because the affordance relation is determined in part by the dynamics of projectile motion, the results imply that the affordance is learned from knowledge of results of throwing

Robot guided 'pen skill' training in children with motor difficulties

Motor deficits are linked to a range of negative physical, social and academic consequences. Haptic robotic interventions, based on the principles of sensorimotor learning, have been shown previously to help children with motor problems learn new movements. We therefore examined whether the training benefits of a robotic system would generalise to a standardised test of 'pen-skills', assessed using objective kinematic measures [via the Clinical Kinematic Assessment Tool, CKAT]. A counterbalanced, cross-over design was used in a group of 51 children (37 male, aged 5-11 years) with manual control difficulties. Improved performance on a novel task using the robotic device could be attributed to the intervention but there was no evidence of generalisation to any of the CKAT tasks. The robotic system appears to have the potential to support motor learning, with the technology affording numerous advantages. However, the training regime may need to target particular manual skills (e.g. letter formation) in order to obtain clinically significant improvements in specific skills such as handwriting.</p

Diet and bone mineral density study in postmenopausal women from the TwinsUK registry shows a negative association with a traditional English dietary pattern and a positive association with wine

Background: The effect of diet on bone mineral density (BMD) remains controversial, mainly because of difficulties in isolating dietary factors from the confounding influences of age, lifestyle, and genetic factors. Objective: The aim of this study was to use a novel method to examine the relation between BMD and diet. Design: A co-twin control study design with linear regression modeling was used to test for associations between BMD and habitual intakes of calcium, vitamin D, protein, and alcohol plus 5 previously identified dietary patterns in postmenopausal women from the TwinsUK registry. This approach exploited the unique matching of twins to provide an estimate of an association that was not confounded by age, genetic background, or shared lifestyle. Results: In >2000 postmenopausal women (BMD data on 1019, 1218, and 1232 twin pairs at the hip neck, hip, and spine, respectively), we observed a positive association between alcohol intake (from wine but not from beer or spirits) and spine BMD (P = 0.01) and a negative association with a traditional 20th-century English diet at the hip neck (P = 0.01). Both associations remained borderline significant after adjustment for mean twin-pair intakes (P = 0.04 and P = 0.055, respectively). Other dietary patterns and intakes of calcium, vitamin D, and protein were unrelated to BMD. Conclusion: Our results showed that diet has an independent but subtle effect on BMD; wine intake was positively associated with spine BMD, whereas a traditional (20th-century) English diet had a negative association with hip BMD

Transfer of learning between unimanual and bimanual rhythmic movement coordination: transfer is a function of the task dynamic.

Under certain conditions, learning can transfer from a trained task to an untrained version of that same task. However, it is as yet unclear what those certain conditions are or why learning transfers when it does. Coordinated rhythmic movement is a valuable model system for investigating transfer because we have a model of the underlying task dynamic that includes perceptual coupling between the limbs being coordinated. The model predicts that (1) coordinated rhythmic movements, both bimanual and unimanual, are organised with respect to relative motion information for relative phase in the coupling function, (2) unimanual is less stable than bimanual coordination because the coupling is unidirectional rather than bidirectional, and (3) learning a new coordination is primarily about learning to perceive and use the relevant information which, with equal perceptual improvement due to training, yields equal transfer of learning from bimanual to unimanual coordination and vice versa [but, given prediction (2), the resulting performance is also conditioned by the intrinsic stability of each task]. In the present study, two groups were trained to produce 90° either unimanually or bimanually, respectively, and tested in respect to learning (namely improved performance in the trained 90° coordination task and improved visual discrimination of 90°) and transfer of learning (to the other, untrained 90° coordination task). Both groups improved in the task condition in which they were trained and in their ability to visually discriminate 90°, and this learning transferred to the untrained condition. When scaled by the relative intrinsic stability of each task, transfer levels were found to be equal. The results are discussed in the context of the perception–action approach to learning and performance