The ecological notion of specification is traditionally understood within a single perceptual modality, with the structure of a given ambient (say optic) energy uniquely related to physical reality. The experiment evaluates the existence of the global array in the context of layout perception, which is often assumed to rely on vision. It formalized an intermodal invariant (i.e., a parameter of the global array) specifying the egocentric distance between a moving observer and astatic object. Three main conditions were tested: Vision-Movement (VM), Vision only (VO), Movement only (MO). Egocentric distance was specified only in the VM condition, and the researchers expected participants to detect it only in that condition. Reachability judgments were precise only when the relation between energy flows was preserved (VM condition). Judgement accuracy in that condition corresponded to the actual reaching distance, but was slightly overestimated (5%). Judgements in the VO and MO conditions were close to random.

Spatial and temporal factors are known to highly influence tactile perception, but their role has been largely unexplored in the case of two-dimensional (2D) pattern recognition. We investigated whether recognition is facilitated by the spatial and/or temporal separation of pattern elements, or by conditions known to favor perceptual integration, such as the ones eliciting apparent movement. 2D vibrotactile patterns were presented to the abdomen of novice participants. In Experiment 1, we manipulated the spatial (inter-tactor distance) and temporal (burst duration and inter-burst interval) parameters applied to the tracing mode (sequential activation of pattern elements). In Experiment 2, we compared display modes differing in their level of temporal overlap in the presentation of pattern elements: the static mode (simultaneous activation of pattern elements), the slit-scan mode (pattern revealed line by line), and the tracing mode. The results of both experiments reveal that (a) recognition performance increases with the isolation of pattern elements in space and/or in time, (b) spatial and temporal factors interact in pattern recognition, and (c) conditions leading to apparent movement tend to be associated with lower recognition accuracy. These results further our understanding of tactile perception and provide guidance for the design of future vibrotactile communication systems. Public Significance Statement This study reveals that patterns made up of several vibration points are better recognized when pattern elements are clearly isolated in time and space. The feeling of a single point moving continuously along the skin, as if the pattern was manually drawn on the skin, does not appear to favor the recognition of patterns' shape.

The aim of this study was to investigate how the affordances of an indoor climbing wall changed for intermediate climbers following a period of practice during which hold orientation was manipulated within a learning and transfer protocol. The learning protocol consisted of four sessions, in which eight climbers randomly ascended three different routes of fixed absolute difficulty (5c on the French scale), as fluently as possible. All three routes were 10.3 m in height and composed of 20 hand-holds at the same locations on an artificial climbing wall; only hold orientations were altered: (i) a horizontal-edge route (H) was designed to afford horizontal hold grasping, (ii) a vertical-edge route (V) afforded vertical hold grasping, and (iii), a double-edge route (D) was designed to afford both horizontal and vertical hold grasping. Five inertial measurement units (IMU) (3D accelerometer, 3D gyroscope, 3D magnetometer) were attached to the hip, feet and forearms to analyze the vertical acceleration and direction (3D unitary vector) of each limb and hip in ambient space during the entire ascent. Segmentation and classification processes supported detection of movement and stationary phases for each IMU. Depending on whether limbs and/or hip were moving, a decision tree distinguished four states of behavior: stationary (absence of limb and hip motion), hold exploration (absence of hip motion but at least one limb in motion), hip movement (hip in motion but absence of limb motion) and global motion (hip in motion and at least one limb in motion). Results showed that with practice, the learners decreased the relative duration of hold exploration, suggesting that they improved affordance perception of hold grasp-ability. The number of performatory movements also decreased as performance increased during learning sessions, confirming that participants' climbing efficacy improved as a function of practice. Last, the results were more marked for the H route, while the D route led to longer relative stationary duration and a shorter relative duration of performatory states. Together, these findings emphasized the benefit of manipulating task constraints to promote safe exploration during learning, which is particularly relevant in extreme sports involving climbing tasks.

J. J. Gibson (1966) rejected many classical assumptions about perception but retained 1 that dates back to classical antiquity: the assumption of separate senses. We suggest that Gibson's retention of this assumption compromised his novel concept of perceptual systems. We argue that lawful, 1:1 specification of the animal–environment interaction, which is necessary for perception to be direct, cannot exist in individual forms of ambient energy, such as light, or sound. We argue that specification exists exclusively in emergent, higher order patterns that extend across different forms of ambient energy. These emergent, higher order patterns constitute the global array. If specification exists exclusively in the global array, then direct perception cannot be based upon detection of patterns that are confined to individual forms of ambient energy and, therefore, Gibson's argument for the existence of several distinct perceptual systems cannot be correct. We argue that the senses function as a single, irreducible perceptual system that is sensitive exclusively to patterns in the global array. That is, rather than distinct perceptual systems there exists only 1 perceptual system.

Analysis of dual sports performance typically involves observational techniques to gather data samples during actual competition. These techniques are limited by the amount of data that can be collected and the need to define the observable variables in advance. Today's advanced technologies have considerably overcome these limitations, enabling high‐volume data collection for post‐recording analysis. The present study was based on the three‐dimensional kinematic data recorded by the automated ball‐tracking Hawk‐Eye system between the 2003 and 2008 seasons in elite tennis tournaments, which provided a database of 262 596 points. The analysis consisted of an examination of the relationships between the various characteristics of the serve summed up by the resulting ball trajectory and winning‐point probabilities. The influence of factors such as serve speed, serve location, court surface, gender differences, and spin intensity on the winning‐point rate was assessed to gain insight into efficient serve tendencies in world‐class tennis. The implications for practitioners are highlighted and directions for future research in tennis performance analysis based on automatic ball tracking are proposed. © 2016 Wiley Periodicals, Inc. Statistical Analysis and Data Mining: The ASA Data Science Journal, 2016

Body movement influences the structure of multiple forms of ambient energy, including optics and gravito-inertial force. Some researchers have argued that egocentric distance is derived from inferential integration of visual and non-visual stimulation. We suggest that accurate information about egocentric distance exists in perceptual stimulation as higher-order patterns that extend across optics and inertia. We formalize a pattern that specifies the egocentric distance of a stationary object across higher-order relations between optics and inertia. This higher-order parameter is created by self-generated movement of the perceiver in inertial space relative to the illuminated environment. For this reason, we placed minimal restrictions on the exploratory movements of our participants. We asked whether humans can detect and use the information available in this higher-order pattern. Participants judged whether a virtual object was within reach. We manipulated relations between body movement and the ambient structure of optics and inertia. Judgments were precise and accurate when the higher-order optical-inertial parameter was available. When only optic flow was available, judgments were poor. Our results reveal that participants perceived egocentric distance from the higher-order, optical-inertial consequences of their own exploratory activity. Analysis of participants’ movement trajectories revealed that self-selected movements were complex, and tended to optimize availability of the optical-inertial pattern that specifies egocentric distance. We argue that accurate information about egocentric distance exists in higher-order patterns of ambient energy, that self-generated movement can generate these higher-order patterns, and that these patterns can be detected and used to support perception of egocentric distance that is precise and accurate.

In the present study, we aim at showing how some characteristics of the serve summed up in the resulting ball trajectory can determine the efficiency of tennis serves. To that purpose, we analyzed a big set of data collected between 2003 and 2008 at international ATP, WTA and Grand Slam tournaments and corresponding to 84 tournaments, 1729 matches, 262,596 points. Using time-dependent three-dimensional ball trajectory data recorded by the automated ball tracking Hawk-Eye system, we show the relationships that exists between the characteristics of the serve kinematics and impacts on the ground on the gain of the points.

AbstractThe design community has growing familiarity with the concept of affordances and with the utility of this concept in many areas of design. Less emphasis has been placed on natural processes by which people acquire knowledge about affordances. Consequently, little is known about how design might be optimized to enable users to detect the actions that are available in a given human–machine system. We review scientific research about what people do to obtain information about affordances. We discuss implications of this research for design.

By primarily focusing on the perceptual information available to an organism and by adopting a functional perspective, the ecological approach to perception and action provides a unique theoretical basis for addressing the remote perception problem raised by telerobotics. After clarifying some necessary concepts of this approach, we first detail some of the major implications of an ecological perspective to robot teleoperation. Based on these, we then propose a framework for coping with the alteration of the information available to the operator. While our proposal shares much with previous works that applied ecological principles to the design of man-machine interfaces (e.g., ecological interface design), it puts a special emphasis on the control of action (instead of process) which is central to teleoperation but has been seldom addressed in the literature.

We investigated the information that supports perception of whether an object is within reach using a locomotor task. Participants adjusted their own position relative to a fixed target by stepping or by propelling a wheelchair until they judged it to be within reach. The to-be-reached object was presented in virtual reality. The display of the target was driven in real time as a function of the observer's movement, thus depicting a stationary virtual object at a definite distance only through the relation across optical and nonoptical patterns of stimulation. We asked participants to judge the distance they could reach with their unaided hand or when holding a rod that extended their effective reach. They could see neither their body nor the rod thereby limiting available visual information about oreachability.o As expected, our results showed that despite the limited information that was available, participants' locomotor adjustments were influenced by (a) their simulated distance from the target, (b) their arm length, and (c) the presence or absence of the rod. The type of motion (stepping or wheelchair) had little influence. However, judgment accuracy was influenced by participants' initial simulated distance from the target. We compare the performance obtained in our locomotor judgment task with previous studies that have used different methods for measuring perceived reaching-ability. We discuss perceptual information that could have supported performance within the framework of the global array.

This paper reports on a study on the perception and rendering of distance in multimodal virtual environments. A model for binaural sound synthesis is discussed, and its integration in a real-time system with motion tracking and visual rendering is presented. Results from a validation experiment show that the model effectively simulates relevant auditory cues for distance perception in dynamic conditions. The model is then used in a subsequent experiment on the perception of egocentric distance. The design and preliminary result from this experiment are discussed.

This commentary highlights the similarities and differences between on the one hand the (Noeian-viewed) concept of enaction defended by Lenay and criticized by Jacob, and on the other hand the Gibsonian, ecological approach to perception and action. In this context, we address the notions of representation, sensation and information, sensori-motor coupling, and inadequacy of efferent copy.

Enactive interfaces must incorporate intuitive activity that characterizes naturalistic perception. However, the manner in which information is presented is not more important than the contents: what information is presented. In this contribution, we address the contents of perception. We argue that people perceive affordances, that is, the possible actions that are available in any given situation. We further argue that enactive interfaces should be designed to optimize presentation of information about the possible actions that are available to a person using the enactive interface. The design of enactive interfaces might be guided by an extension of the theory of ecological interface design (Vicente in Hum Factors 44:62–78, 2002 ) to include multimodal information that is accessed through fast, intuitive exploratory movement. We review two empirical studies that illustrate our arguments. Careful analysis of affordances, together with our increasing understanding of the enactive perception of affordances, should influence the design of enactive interfaces.