The illusion of having a large virtual body biases action-specific perception in patients with mild cognitive impairment

The illusion of having a large body makes us perceive objects as smaller than they really are. This action-specific perception effect occurs because we perceive the property of an object (i.e., size) differently according to our unique action capability (i.e., the affordance of body size). Although the body-ownership illusion contributing to this action-specific perception has been studied, its effects remain unclear in neurological patients. We examined the action-specific perception impairments of MCI patients by means of body-ownership illusion in a non-immersive virtual reality environment. Twenty healthy young adults, 21 healthy older adults, and 15 MCI patients were recruited. We assessed their “original-body action-specific perception” and “enlarged-body action-specific perception” using the original and enlarged sizes of their virtual bodies, respectively. The MCI patients’ original-body action-specific perception was no different than that of the healthy controls (p = 0.679). However, the enlarged-body action-specific perception of the MCI patients was significantly biased (p < 0.001). The inclusion of the enlarged-body action-specific perception provides additional discriminative power for early diagnosis of MCI (89.3% accuracy, 75.0% sensitivity, 100.0% specificity, and 87.5% balanced accuracy).

Obstacles Affect Perceptions of Egocentric Distances in Virtual Environments

Distance perception in humans can be affected by oculomotor and optical cues and a person’s action capability in a given environment, known as action-specific effects. For example, a previous study has demonstrated that egocentric distance estimation to a target is affected by the width of a transparent barrier placed in the intermediate space between a participant and a target. However, the characteristics of a barrier’s width that affect distance perception remain unknown. Therefore, we investigated whether visual and tactile inputs and actions related to a barrier affect distance estimation to a target behind the barrier. The results confirmed previous studies by demonstrating that visual and tactile presentations of the barrier’s width affected distance estimation to the target. However, this effect of the barrier’s width was not observed when the barrier was touchable but invisible nor when the barrier was visible but penetrable. These findings indicate the complexity of action-specific effects and the difficulty of identifying necessary information for inducing these effects.

The influence of skill and task complexity on perception of nested affordances

This study investigated how skill level and task complexity influence the calibration of perception–action and particularly how close an individual acts relative to his or her maximal action capabilities. Complexity was manipulated between two (Touch, Grasp) and more than two (Removing, Moving Up) nested affordance conditions. For all conditions, we examined whether advanced climbers had greater maximal action capabilities than intermediate climbers or whether they better scaled their action (i.e., acted nearer to their maximal action capabilities) or both. Eleven intermediate and 11 advanced male climbers were first asked to estimate the maximum distance that they could reach a climbing hold. The hold was moved along a slide and fixed once requested by the participant; subsequently, the distance to the starting hold was measured. After each estimation, the participant was required to execute the climbing action. After four estimation-action trials in each of the four conditions, the maximal action capability (i.e., actual maximal reaching distance) was determined. Advanced climbers demonstrated greater actual maximal reaching distances than intermediate climbers for all conditions, but they only estimated greater maximal reaching distances for the more complex conditions, which featured more than two nested affordances. When estimated maximal reaching distances were scaled to actual maximal reaching distances, advanced climbers did not differ from intermediate climbers for any condition, and there were no differences between conditions. Our findings indicate that expertise was a function of greater action capabilities, but not due to the accuracy of calibration.

Body size perception in stroke patients with paresis

Recent studies have suggested that people’s intent and ability to act also can influence their perception of their bodies’ peripersonal space. Vice versa one could assume that the inability to reach toward and grasp an object might have an impact on the subject’s perception of reaching distance. Here we tested this prediction by investigating body size and action capability perception of neurological patients suffering from arm paresis after stroke, comparing 32 right-brain-damaged patients (13 with left-sided arm paresis without additional spatial neglect, 10 with left-sided arm paresis and additional spatial neglect, 9 patients had neither arm paresis nor neglect) and 27 healthy controls. Nineteen of the group of right hemisphere stroke patients could be re-examined about five months after initial injury. Arm length was estimated in three different methodological approaches: explicit visual, explicit tactile/proprioceptive, and implicit reaching. Results fulfilled the working hypothesis. Patients with an arm paresis indeed perceived their bodies differently. We found a transient overestimation of the length of the contralesional, paretic arm after stroke. Body size and action capability perception for the extremities thus indeed seem to be tightly linked in humans.

It’s in your hands: How variable perception affects grasping estimates in virtual reality

Successful interaction within one’s environment is contingent upon one’s ability to accurately perceive the extent over which actions can be performed, referred to as action boundaries. As our possibilities for action are subject to variability, it is necessary for individuals to be able to update their perceived action boundaries to accommodate for variance. While research has shown that individuals can update their action boundaries to accommodate for variability, it is unclear how the perceptual system calibrates to this variance to inform our action boundaries. This study investigated the influence of perceptual motor variability by analysing the effect of random and systematic variability on perceived grasp ability in virtual reality. Participants estimated grasp ability following perceptual-motor experience with a constricted, normal, extended, or variable grasp. In Experiment 1, participants experienced all three grasping abilities (constricted, normal, extended) 33% of the time. In Experiment 2 participants experienced the constricted and normal grasps 25% of the time, and the extended grasp 50% of the time. The results indicated that when perceptual-motor feedback is inconsistent, the perceptual system disregards the frequency of perceptual-motor experience with the different action capabilities and considers each action capability experienced as a type, and subsequently calibrates to the average action boundary experienced by type.

Autonomous Capability Evaluation of Ground-Attack UAV Based on Cloud Model and Combined Weight Theory

The evaluation for autonomous capability of ground-attack unmanned aerial vehicle (UAV) comes from the demand of reality, which determines the operational use of airborne equipment authority. It essentially entails a multicriteria decision-making process accounting for evaluation model and uncertainties. Firstly, as for the construction of evaluation model, the index model is proposed from four aspects of observation capability, decision capability, action capability, and security capability, namely, ODAS, which analogizes cognitive behavior mechanism of human based on airborne equipment; then, to solve uncertainties of randomness and fuzziness in the process of autonomous capability evaluation, a cloud model approach is proposed, which expresses uncertainties by the certainty degree distribution. Finally, the cloud model-based approach is tested by evaluating typical UAVs and comparing with Hopfield neural network method. The results show that the evaluation of the autonomous capability based on the cloud model is accurate and more representative than the Hopfield neural network method.

The Pong Effect as a Robust Visual Illusion: Evidence From Manipulating Instructions

Visual perception is not always veridical but can be influenced by factors such as ease of acting, energetic cost, and even body type of the observer. This notion is called action-specific perception. Several effects of action capability on visual perception have been found, but there is much controversy as to whether these effects are truly perceptual. Because perception cannot be measured directly, resolving the controversy relies on ruling out alternative explanations through systematic testing. We combined one of the most robust action-specific effects (the Pong effect) with one of the primary suggestions for exploring an alternative explanation, namely whether the effect persists across instructions that emphasize different aspects of the task. The Pong effect was robust to the type of instructions. The results provide critical evidence that the Pong effect is truly perceptual, furthering the argument that a person’s ability to act can influence visual perception.

Do exploratory arm movements contribute to maximum reach distance judgements?

Exploratory movements provide information about agents’ action capabilities in a given environment. However, little is known about the specifics of these exploratory movements, such as which movements are necessary to perceive a given action capability. This experiment tested whether arm movements contributed to judgements of maximum reach distance. Participants made judgements about their maximum reach distance by walking to the point farthest from an object from which they still perceived the object to be reachable. Over the course of two sets of nine judgements, participants’ arms either swung naturally by their sides (Unrestricted Condition) or were held together behind their backs (Restricted Condition). Arm movement restriction increased maximum reach distance judgement error when compared with unrestricted judgements. In addition, judgement error improved over trials only when exploratory arm movements were unrestricted, and the improvements did not carry over to subsequent judgements made when exploratory arm movements were restricted. Arm movement restriction did not increase the variability of judgement error when compared with unrestricted judgements. The results indicate that exploration is necessary to generate affordance information, show that restricted exploration degrades affordance perception, and suggest that maximum reach distance exists at the global array level. In addition, they have practical implications for operational situations in which actors’ arm movements are restricted, such as when military personnel wear body armour.

Perfect Tunable All-Optical Diode based on Periodic Photonic Crystal Grand Graded Structures

We have investigated nonlinear properties and optically diode action capability in graded nonlinear one-dimensional photonic crystals-made up of graded index and thickness layers using transfer matrix method (TMM). We have considered the efficacy of index and thickness gradient parameters on the nonlinear properties in right to left and left to right optical pumping. It is found that the difference between the up-switch threshold input intensities of the left to right and right to left impinging lights and optical bistability (OBS) threshold can be tunable with thickness gradation parameter and index gradation parameter, respectively. Proposed structure can be useful in designing low threshold and high speed optical diode, switches and rectifiers.