Geoffrey P. Bingham

Task Specific Devices and the Perceptual Bottleneck

An approach to the problem of organization in human action is presented. The approach describes the observable forms of behavior in terms of the dynamics of task-specific devices (TSD). The properties of a TSD delineate problems for research. The properties are task specificity, smartness, determinism, soft assembly and reduction, controllability, scale specificity, assembly over properties of organism and environment, and modifiability to new purpose. Nonlinear properties of four subsystems of the human action system are described. The subsystems are the link-segment system, the musculotendon system, the circulatory system, and the nervous system. A methodological dilemma is created by the need to do justice in description to all four subsystems while at the same time not being completely overwhelmed by the extreme complexity. A strategic resolution is to describe the simpler dynamics of TSDs. This strategy holds the promise of working backwards to the complex dynamics of the subsystems from which a TSD is assembled. Finally, TSDs require perceptual access to the dynamics. The characteristics of the human perceptual system lead to the perceptual bottleneck. Information about the dynamics of actions and events must be preserved over two mappings. One mapping is from the dynamics to the kinematics of an event. This introduces the identification problem in perception. How do the qualitative properties of an event allow an observer to recognize it? The second mapping is from the ratio-scaled kinematics of an event to the nonratio-scaled structure of the optic, acoustic, and haptic arrays. This introduces the scaling problem in perception. How do the qualitative properties of an event allow an observer to judge the scale values in an event?

Kinematic Form and Scaling: Further Investigations on the Visual Perception of Lifted Weight

Observers are able to judge accurately the weight lifted by another person when only the motions of reflective patches attached to the lifters major limb joints and head can be seen (Runeson & Frykholm, 1981). What properties of these complex kinematic patterns allow judgments of weight to be made? The pattern of variation in velocity of the lifted object over position is explored as a source of information for weight: It is found to provide limited information. How are variations in kinematic patterns scaled to allow judgments of weight, a kinetic quantity? The possibility of a source of information for scaling in the kinematics is investigated. Judgments based only on patch-light displays are accurate to a degree that is improved by an extrinsic scaling basis. Finally, the sensitivity to scaling of alternative metrics used in judging is explored. Intrinsic metrics are discovered to be less sensitive to the absence of an extrinsic basis for scaling.

Hefting for a Maximum Distance Throw: A Smart Perceptual Mechanism*

Objects for throwing to a maximum distance were selected by hefting objects varying in size and weight. Preferred weights increased with size reproducing size-weight illusion scaling between weight and volume. In maximum distance throws, preferred objects were thrown the farthest. Throwing was related to hefting as a smart perceptual mechanism. Two strategies for conveying high kinetic energy to projectiles were investigated by studying the kinematics of hefting light, preferred, and heavy objects. Changes in tendon lengths occurring when objects of varying size were grasped corresponded to changes in stiffness at the wrist. Hefting with preferred objects produced an invariant phase between the wrist and elbow. This result corresponded to an optimal relation at peak kinetic energy for the hefting. A paradigm for the study of perceptual properties was compared to size-weight illusion methodology.

Visual perception of mean relative phase and phase variability

Perception of relative phase and phase variability may play a fundamental role in interlimb coordination. This study was designed to investigate the perception of relative phase and of phase variability and the stability of perception in each case. Observers judged the relative phasing of two circles rhythmically moving on a computer display. The circles moved from side to side, simulating movement in the frontoparallel plane, or increased and decreased in size, simulating movement in depth. Under each viewing condition, participants observed the same displays but were to judge either mean relative phase or phase variability. Phase variability interfered with the mean-relative-phase judgments, in particular when the mean relative phase was 0 degrees. Judgments of phase variability varied as a function of mean relative phase. Furthermore, the stability of the judgments followed an asymmetric inverted U-shaped relation with mean relative phase, as predicted by the Haken-Kelso-Bunz model.

Visual perception of the relative phasing of human limb movements

Studies of bimanual coordination have found that only two stable relative phases (0° and 180°) are produced when a participant rhythmically moves two joints in different limbs at the same frequency. Increasing the frequency of oscillation causes an increase in relative phase variability in both of these phase modes. However, relative phasing at 180° is more variable than relative phasing at 0°, and when the frequency of oscillation reaches a critical frequency, a transition to 0° occurs. These results have been replicated when 2 people have coordinated their respective limb movements using vision. This inspired us to investigate the visual perception of relative phase. In Experiment 1, recordings of human interlimb oscillations exhibiting different frequencies, mean relative phases, and different amounts of phase variability were used to generate computer displays of spheres oscillating either side to side in a frontoparallel plane or in depth. Participants judged the stability of relative phase. Judgments covaried with phase variability only when the mean phase was 0° or 180°. Otherwise, judgments covaried with mean relative phase, even after extensive instruction and demonstration. In Experiment 2, mean relative phase and phase variability were manipulated independently via simulations, and participants were trained to perceive phase variability in testing sessions in which mean phase was held constant. The results of Experiment 1 were replicated. The HKB model was fitted to mean judgment standard deviations.

Dynamics and the orientation of kinematic forms in visual event recognition.

The authors investigated event dynamics as a determinant of the perceptual significance of forms of motion. Patch-light displays were recorded for 9 simple events selected to represent rigid-body dynamics, biodynamics, hydrodynamics, and aerodynamics. Observers described events in a free-response task or by circling properties on a list. Cluster analyses performed on descriptor frequencies reflected the dynamics. Observers discriminated hydro- versus aerodynamic events and animate versus inanimate events. The latter result was confirmed by using a forced-choice task. Dynamical models of the events led us to consider energy flows as a determinant of kinematic properties that allowed animacy to be distinguished. Orientation was manipulated in 3 viewing conditions. Descriptions varied with absolute display orientation rather than the relative orientation of display and observer.

Accommodation, occlusion, and disparity matching are used to guide reaching: a comparison of actual versus virtual environments.

The authors used a virtual environment to investigate visual control of reaching and monocular and binocular perception of egocentric distance, size, and shape. With binocular vision, the results suggested use of disparity matching. This was tested and confirmed in the virtual environment by eliminating other information about contact of hand and target. Elimination of occlusion of hand by target destabilized monocular but not binocular performance. Because the virtual environment entails accommodation of an image beyond reach, the authors predicted overestimation of egocentric distances in the virtual relative to actual environment. This was confirmed. The authors used -2 diopter glasses to reduce the focal distance in the virtual environment. Overestimates were reduced by half. The authors conclude that calibration of perception is required for accurate feedforward reaching and that disparity matching is optimal visual information for calibration.

Perceptual coupling in rhythmic movement coordination: stable perception leads to stable action

Rhythmic movement coordination exhibits characteristic patterns of stability, specifically that movements at 0° mean relative phase are maximally stable, 180° is stable but less so than 0°, and other coordinations are unstable without training. Recent research has demonstrated a role for perception in creating this pattern; perceptual variability judgments covary with movement variability results. This suggests that the movement results could be due in part to differential perceptual resolution of the target movement coordinations. The current study used a paradigm that enabled simultaneous access to both perception (between-trial) and movement (within-trial) stability measures. A visually specified 0° target mean relative phase enabled participants to produce stable movements when the movements were at a non-0° relationship to the target being tracked. Strong relationships were found between within-trial stability (the traditional movement measure) and between-trial stability (the traditional perceptual judgment measure), suggestive of a role for perception in producing coordination stability phenomena. The stabilization was incomplete, however, indicating that visual perception was not the sole determinant of movement stability. Rhythmic movement coordination is intrinsically a perception/action system.

Task Dynamics and Resource Dynamics in the Assembly of a Coordinated Rhythmic Activity

Task dynamics corresponding to rhythmic movements emerge from interactions among dynamical resources composed of the musculature, the link segments, and the nervous and circulatory systems. This article investigated whether perturbations of interlimb coordination might be effect over circulatory and nervous elements. Stiffness of wrist-pendulums oscillated at a common tempo and at 180 degrees relative phase was perturbed through the use of tonic activity about an ankle. Left and right stiffnesses, the common period, and the phase relation all changed. Stiffnesses increased with ankle torque in proportion to the wrists inertial load. Despite different changes in stiffness at the two wrists, isochrony was preserved. The stability was shown to be consistent with the proportionality of changes in stiffness to the inertial loads. The phase departed from antiphase in proportion to the asymmetry of inertial loads. The size of departures decreased with increasing ankle torque. An account was developed in terms of muscular, circulatory, and nervous functions.

Comparing Measures of Monocular Distance Perception: Verbal and Reaching Errors Are Not Correlated

Monocular perception of egocentric distance via optic flow generated by head movement toward a target was investigated with a helmet-mounted video camera and display. Ability to perceive target distance was assessed with 2 response measures: verbal reports and reaches. Systematic and random errors differed as a function of the response measure. Verbal estimates of targets within and beyond reach were obtained before and after the performance of reaches to targets within reach. Systematic errors of verbal estimates changed but did not decrease overall. Random error decreased. Verbal estimates and reaches were performed concurrently to targets within reach. Verbal and reaching errors were uncorrelated. Verbal judgments appear to have been anchored using the range of distances experienced while reaching rather than being calibrated to the perceptual information itself. Discussion focuses on the advantages of action response measures.