A unified fielder theory for interception of moving objects either above or below the horizon

The role of prediction and visual tracking strategies during manual interception: An exploration of individual differences

The interception (or avoidance) of moving objects is a common component of various daily living tasks; however, it remains unclear whether precise alignment of foveal vision with a target is important for motor performance. Furthermore, there has also been little examination of individual differences in visual tracking strategy and the use of anticipatory gaze adjustments. We examined the importance of in-flight tracking and predictive visual behaviors using a virtual reality environment that required participants (n = 41) to intercept tennis balls projected from one of two possible locations. Here, we explored whether different tracking strategies spontaneously arose during the task, and which were most effective. Although indices of closer in-flight tracking (pursuit gain, tracking coherence, tracking lag, and saccades) were predictive of better interception performance, these relationships were rather weak. Anticipatory gaze shifts toward the correct release location of the ball provided no benefit for subsequent interception. Nonetheless, two interceptive strategies were evident: 1) early anticipation of the ball's onset location followed by attempts to closely track the ball in flight (i.e., predictive strategy); or 2) positioning gaze between possible onset locations and then using peripheral vision to locate the moving ball (i.e., a visual pivot strategy). Despite showing much poorer in-flight foveal tracking of the ball, participants adopting a visual pivot strategy performed slightly better in the task. Overall, these results indicate that precise alignment of the fovea with the target may not be critical for interception tasks, but that observers can adopt quite varied visual guidance approaches.

The geometry of consciousness

Conscious experience implies a reference-frame or vantage, which is often important in scientific models. Control models of ball-interception are used as an example. Models that use viewer-dependent egocentric reference-frames are contrasted with viewer-independent allocentric ones. Allocentric reference-frames serve well for models like Newtonian physics, which utilize static coordinate-systems that allow forces and object-movements to be compartmentalized. In contrast, egocentric reference-frames are natural for modeling mobile organisms or robots when controlling perception-action behavior. Lower-level perception-action behavior is often characterized using egocentric coordinate-systems that optimize processing-speed, while higher-level cognitive-processes use allocentric frames that provide a stationary spatial reference. Brain-behavior models like the Ventral-Stream What System, and Dorsal-Stream Where-How System, also respectively utilize allocentric and egocentric reference-frames. Reference-frame clarification can resolve disputes about models of control-tasks like running to catch baseballs, and can provide insights for biomimetic-robots. Confusion regarding geometry and reference-frames contributes to a lack of clarity between how and when egocentric versus allocentric geometries are imposed, with perception-actions generally being more egocentric and conscious experience more allocentric.

Mapping Time-to-Contact and Time-to-Peak Effector Velocity in Interceptive Striking Tasks

PURPOSE

This study investigated perception and action coupling as reflected in a mapping between time-to-contact (TTC) and time-to-peak-velocity (TPV) for children and youths aged 7 to 8, 11 to 12, and 15 to 16 years old and adults aged 19 to 20 years old performing a task that allowed the participants to self-select the interception position in a baseball-like batting game on a graphics tablet.

METHOD

The moving object to be hit for distance had curvilinear trajectories toward the hitter that were determined by simulated weightings of gravity and velocity.

RESULTS

Successful interceptions in all age groups were characterized by a mapping of mean TTC and TPV and a higher correlation of these variables with increasing age. The object was hit at approximately 90% TPV so that the implement was still accelerating on contact-an adaptive task feature for a striking distance criterion.

CONCLUSION

The results are consistent with theories of perception-action coupling that are congruent with the ecological and dynamical approaches to action where TTC, a source of environmental information, is mapped relative to TPV, largely independent of the particular kinematic task demands of the approaching object. The organization of the coupling of TTC prior to TPV was evident across all age groups and is evidence for a common strategy for this type of interceptive action. The age-related changes in the strength of the relationship between TTC and TPV are evidence of increased sensitivity to the coupling between TTC and TPV.

Navigational strategy used to intercept fly balls under real-world conditions with moving visual background fields

This study explored the navigational strategy used to intercept fly balls in a real-world environment under conditions with moving visual background fields. Fielders ran across a gymnasium attempting to catch fly balls that varied in distance and direction. During each trial, the launched balls traveled in front of a moving background texture that was projected onto an entire wall of a gymnasium. The background texture consisted of a field of random dots that moved together, at a constant speed and direction that varied between trials. The fielder route deviation was defined as the signed area swept out between the actual running path and a straight-line path to the destination, and these route deviation values were compared as a function of the background motion conditions. The findings confirmed that the moving visual background fields systematically altered the fielder running paths, which curved more forward and then to the side when the background gradient moved laterally with the ball, and curved more to the side and then forward when the background gradient moved opposite the ball. Fielder running paths deviated systematically, in a manner consistent with the use of a geometric optical control strategy that helps guide real-world perception-action tasks of interception, such as catching balls.

Keeping your eyes continuously on the ball while running for catchable and uncatchable fly balls

When faced with a fly ball approaching along the sagittal plane, fielders need information for the control of their running to the interception location. This information could be available in the initial part of the ball trajectory, such that the interception location can be predicted from its initial conditions. Alternatively, such predictive information is not available, and running to the interception location involves continuous visual guidance. The latter type of control would predict that fielders keep looking at the approaching ball for most of its flight, whereas the former type of control would fit with looking at the ball during the early part of the ball's flight; keeping the eyes on the ball during the remainder of its trajectory would not be necessary when the interception location can be inferred from the first part of the ball trajectory. The present contribution studied visual tracking of approaching fly balls. Participants were equipped with a mobile eye tracker. They were confronted with tennis balls approaching from about 20 m, and projected in such a way that some balls were catchable and others were not. In all situations, participants almost exclusively tracked the ball with their gaze until just before the catch or until they indicated that a ball was uncatchable. This continuous tracking of the ball, even when running close to their maximum speeds, suggests that participants employed continuous visual control rather than running to an interception location known from looking at the early part of the ball flight.

The visual system's intrinsic bias influences space perception in the impoverished environment

A dimly lit target in the intermediate distance in the dark is judged at the intersection between the target's projection line from the eye to its physical location and an implicit slanted surface, which is the visual system's intrinsic bias. We hypothesize that the intrinsic bias also contributes to perceptual space in the impoverished environment. We first showed that a target viewed against sparse texture elements delineating the horizontal ground surface in the dark is localized along an implicit slanted surface that is less slanted than that of the intrinsic bias, reflecting the weighted integration of the weak texture information and intrinsic bias. We also showed that while the judged egocentric locations are similar between 0.15- to 5-s exposure durations, the judged precision improves with duration. Furthermore, the precision for the judged target angular declination does not vary with the physical angular declination and is better than the precision of the eye-to-target distance. Second, we used both action and perceptual tasks to directly reveal the perceived surface slant. Confirming our hypothesis, we found that an L-shaped target on the horizontal ground with sparse texture information is perceived with a slant that is less than that of the intrinsic bias.

A dynamical systems account of sensorimotor contingencies

According to the sensorimotor approach, perception is a form of embodied know-how, constituted by lawful regularities in the sensorimotor flow or in sensorimotor contingencies (SMCs) in an active and situated agent. Despite the attention that this approach has attracted, there have been few attempts to define its core concepts formally. In this paper, we examine the idea of SMCs and argue that its use involves notions that need to be distinguished. We introduce four distinct kinds of SMCs, which we define operationally. These are the notions of sensorimotor environment (open-loop motor-induced sensory variations), sensorimotor habitat (closed-loop sensorimotor trajectories), sensorimotor coordination (reliable sensorimotor patterns playing a functional role), and sensorimotor strategy (normative organization of sensorimotor coordinations). We make use of a minimal dynamical model of visually guided categorization to test the explanatory value of the different kinds of SMCs. Finally, we discuss the impact of our definitions on the conceptual development and empirical as well as model-based testing of the claims of the sensorimotor approach.

Receivers in American Football Use a Constant Optical Projection Plane Angle to Pursue and Catch Thrown Footballs

In the present work we test how well two interceptive strategies, which have been proposed for catching balls hit high in the air in baseball and cricket, account for receivers in American football catching footballs. This is an important test of the domain generality of these strategies as this is the first study examining a situation where the pursuer's locomotor axis is directed away from the origin of the ball, and because the flight characteristics of an American football are far different from targets studied in prior work. The first strategy is to elicit changes in the ball's lateral optical position that match changes in the vertical optical position so that the optical projection plane angle, ψ, remains constant, thus resulting in a linear optical trajectory (LOT). The second is keeping vertical optical ball velocity decreasing while maintaining constant lateral optical velocity (generalized optical acceleration cancellation, or GOAC). We found that the optical projection plane angle was maintained as constant significantly more often than maintaining vertical and lateral optical velocities as GOAC predicted. The present experiment extends previous research by showing that the constancy of ψ resulting in an LOT is used by humans pursuing American footballs and demonstrates the domain generality of the LOT heuristic.

Synchronizing self and object movement: how child and adult cyclists intercept moving gaps in a virtual environment

Two experiments examined how 10- and 12-year-old children and adults intercept moving gaps while bicycling in an immersive virtual environment. Participants rode an actual bicycle along a virtual roadway. At 12 test intersections, participants attempted to pass through a gap between 2 moving, car-sized blocks without stopping. The blocks were timed such that it was sometimes necessary for participants to adjust their speed in order to pass through the gap. We manipulated available visual information by presenting the target blocks in isolation in Experiment 1 and in streams of blocks in Experiment 2. In both experiments, adults had more time to spare than did children. Both groups had more time to spare when they were required to slow down than when they were required to speed up. Participants' behavior revealed a multistage interception strategy that cannot be explained by the use of a monotonic control law such as the constant bearing angle strategy. The General Discussion section focuses on possible sources of changes in perception-action coupling over development and on task-specific constraints that could underlie the observed interception strategy.