Movement Speed and Accuracy in Space and Time: The Complementarity of Error Distributions

Movement speed-accuracy trade-off is a function of the space-time constraints of the task. We investigated the space-time account of Hancock and Newell (1985) and the hypothesis of complementarity between the four moments of the error distribution in space and time. Twelve participants performed 15 conditions in a line drawing task composed of different spatial (10, 20, and 30 cm) and temporal (250 to 2,500 ms) criteria. The results showed that all moments of distributions changed systematically between conditions but there were some departures from the Hancock and Newell predictions. In contrast, individual analysis revealed the complementarity of the spatial and temporal error including a trade-off between the four moments of error. These findings support a complementary space-time account of movement speed and accuracy.     

Response Timing Accuracy as a Function of Movement Velocity and Distance

In two experiments, patterns of response error during a timing accuracy task were investigated. In Experiment 1. these patterns were examined across a full range of movement velocities, which provided a test of the hypothesis that as movement velocity increases, constant error (CE) shifts from a negative to a positive response bias, with the zero CE point occurring at approximately 50% of maximum movement velocity (Hancock & Newell, 1985). Additionally, by examining variable error (VE), timing error variability patterns over a full range of movement velocities were established. Subjects (N = 6) performed a series of forearm flexion movements requiring 19 different movement velocities. Results corroborated previous observations that variability of timing error primarily decreased as movement velocity increased from 6 to 42% of maximum velocity. Additionally, CE data across the velocity spectrum did not support the proposed timing error function. In Experiment 2, the effect(s) of responding at 3 movement distances with 6 movement velocities on response timing error were investigated. VE was significantly lower for the 3 high-velocity movements than for the 3 low-velocity movements. Additionally, when MT was mathematically factored out. VE was less at the long movement distance than at the short distance. As in Experiment 1, CE was unaffected by distance or velocity effects and the predicted CE timing error function was not evident.     

On the Role of Visual Afferent Information for the Control of Aiming Movements Toward Targets of Different Sizes

The authors investigated (a) whether the specificity of practice hypothesis is mediated by the importance of visual afferent information for the control of manual aiming movements and (b) how movement planning and online correction processes to the movement initial impulse are affected by the withdrawal of visual information in transfer. In acquisition, participants (N = 40) aimed at targets of different sizes in a full-vision or in a target-only condition before being transferred to a target-only condition without knowledge of results. The results supported the hypothesis that learning is specific to the source or sources of afferent information that are more likely to ensure optimal performance. The results also suggested that individuals will not always use visual afferent information more extensively when aiming at a small rather than at a large target. Instead, in a temporally constrained task, the relative efficiency of visually based corrections appears to mediate how exclusively an individual will rely on online visual afferent information for movement control. Finally, the detailed kinematic analysis performed in the present study clearly indicated that online modifications to the movement primary impulse are possible, arguing for a continuous or pseudo-continuous control of relatively slow aiming movements on the basis of visual afferent input.     

Shared timing variability in eye and finger movements increases with interval duration: Support for a distributed timing system below and above one second

The origins of the ability to produce action at will at the hundreds of millisecond to second range remain poorly understood. A central issue is whether such timing is governed by one mechanism or by several different mechanisms, possibly invoked by different effectors used to perform the timing task. If two effectors invoke similar timing mechanisms, then they should both produce similar variability increase with interval duration (interonset interval) and thus adhere to Weber's law (increasing linearly with the duration of the interval to be timed). Additionally, if both effectors invoke the same timing mechanism, the variability of the effectors should be highly correlated across participants. To test these possibilities, we assessed the behavioural characteristics across fingers and eyes as effectors and compared the timing variability between and within them as a function of the interval to be produced (interresponse interval). Sixty participants produced isochronous intervals from 524 to 1431?ms with their fingers and their eyes. High correlations within each effector indicated consistent performance within participants. Consistent with a single mechanism, temporal variability in both fingers and eyes followed Weber's law, and significant correlations between eye and finger variability were found for several intervals. These results can support neither the single clock nor the multiple clock hypotheses but instead suggest a partially overlapping distributed timing system.     

Introduction: Toward a Fully Human Theory of Evolution

During the 20th century two major ventures were launched to advance Darwinian evolution theory. Both involved historic visions and were vital steps for science and society, but then something happened on the way to the millennium. By mid-century the first venture had become a virtual scientific monopoly governed by the biology of the neoDarwinian paradigm. The second venture then set out in the 1980s to remedy the inadequacies of the neoDarwinian paradigm by widening the prospects for evolution theory. But overwhelmed by the underlying mismatch between scientific abstraction and evolutionary reality the first venture established, it soon settled into a fierce attempt to further expand the territory for the neoDarwinian monopoly into what became a militant ideology for sociobiology and evolutionary psychology. This special issue of World Futures contains the papers of a small "task force" of the General Evolution Research Group that set out in the summer of 2000 to try to put behind us what increasingly looms as the "old" paradigm, as well as the "old" story, of evolution.     

The Efficiency of Skilled Performance

The observed ease or effort of performance has traditionally been considered an integral part of any definition of skill (e.g., Guthrie, 1935). Empirical investigations of skill learning and performance have, however, largely ignored the effort or efficiency with which the movement is performed. This situation has arisen despite the fact that in many skills, particularly athletic endurance events or industrial work tasks, efficiency of performance may be essential to the goal of the task. This paper focuses on the energy demand of various skills and its relationship to issues of learning, performance, and individual differences in preferred rhythm. It is shown that across a variety of tasks the individual’s freely chosen work-rate is the most efficient. The significance of preferred rhythm to theoretical perspectives on rhythmic activity is discussed.     

Toward a Connectionist Model of Recursion in Human Linguistic Performance

Naturally occurring speech contains only a limited amount of complex recursive structure, and this is reflected in the empirically documented difficulties that people experience when processing such structures. We present a connectionist model of human performance in processing recursive language structures. The model is trained on simple artificial languages. We find that the qualitative performance profile of the model matches human behavior, both on the relative difficulty of center-embedding and cross-dependency, and between the processing of these complex recursive structures and right-branching recursive constructions. We analyze how these differences in performance are reflected in the internal representations of the model by performing discriminant analyses on these representations both before and after training. Furthermore, we show how a network trained to process recursive structures can also generate such structures in a probabilistic fashion. This work suggests a novel explanation of people's limited recursive performance, without assuming the existence of a mentally represented competence grammar allowing unbounded recursion.     

Weber (Slope) Analyses of Timing Variability in Tapping and Drawing Tasks

Timing variability in continuous drawing tasks has not been found to be correlated with timing variability in repetitive finger tapping in recent studies (S. D. Robertson et al., 1999; H. N. Zelaznik, R. M. C. Spencer, & R. B. Ivry, 2002). Furthermore, the central component of timing variability, as measured by the slope of the timing variance versus the square of the timed interval, differed for tapping and drawing tasks. On the basis of those results, the authors posited that timing in tapping is explicit and as such uses a central representation of the interval to be timed, whereas timing in drawing tasks is implicit, that is, the temporal component is an emergent property of the trajectory produced. The authors examined that hypothesis in the present study by determining the linear relationship between timing variance and squared duration for tapping, circle-drawing, and line-drawing tasks. Participants (N = 501 performed 1 of 5 tasks: finger tapping, line drawing in the x dimension, line drawing in the y dimension, continuous circle drawing timed in the x dimension, or continuous circle drawing timed in the y dimension. The slopes differed significantly between finger tapping, line drawing, and circle drawing, suggesting separable sources of timing variability. The slopes of the 2 circle-drawing tasks did not differ from one another, nor did the slopes of the 2 line-drawing tasks differ significantly, suggesting a shared timing process within those tasks. Those results are evidence of a high degree of specificity in timing processes.     

Effect of Instructions Prioritizing Speed or Accuracy on Kinematics and Kicking Performance in Football Players

The authors' purpose was to investigate if there is a speed accuracy trade-off in soccer kicking by using instructions prioritizing velocity, accuracy, or both upon soccer kicking performance and kicking direction in experienced soccer players. In addition, kinematics were measured to investigate the eventual differences in performance. Thirteen experienced male footballers performed penalty kicks with different instructions prioritizing velocity, accuracy or both. Three-dimensional kinematics, together with maximal ball velocity and hitting accuracy, were measured on all kicks. The main findings were that when the main aim was accuracy, accuracy increased, while the velocity reduced, which supports Fitts' law (Fitts, 1954 Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47, 381–391.[Crossref], [PubMed] , [Google Scholar]). In addition, kicking accuracy was higher when kicking to the contralateral side. The slower ball velocity was caused by lower segmental and in run velocities. These lower segmental velocities were mainly caused by the lower maximal knee extension and pelvis rotation during the accuracy priority kicks.     

Blocking in Rapid Finger Tapping: The Role of Variability in Proximodistal Coordination

In rapid finger tapping, occasional intertap intervals of about twice the normal length or even longer, called blockings, can be observed. Skilled rapid tapping requires that flexor and extensor activity be timed so that they coincide with certain phases of the finger movement. In the present study, the hypothesis examined was that blockings are associated with a deviation from the proper timing relations between the more proximal signals (electromyographic [EMG] bursts) and the more distal signal (position-time curve of the finger). Participants (N = 8) performed up-and-down tapping. Blockings were compared with the preceding normal tapping cycles; a temporal forward shift of the flexor burst in the time interval between two kinematic landmarks—the lifting of the finger and the reversal of the movement—was found consistently in the blockings The phase shift of the flexor burst relative to the kinematic landmarks did not develop gradually in the course of the tapping cycles that preceded the blocking but was an abrupt deviation, which suggests that blockings occur with an increased likelihood as the extremes of the normal variability of the phase relation are approached.     

Performance and Learning of Generalized Motor Programs: Relative (GMP) and Absolute (Parameter) Errors

The effects of practice (Experiment 1) and parameter variability (Experiment 2) on the learning of generalized motor programs (GMPs) and movement parameterization were investigated In each experiment, 2 tasks with different relative force-time structures were tested. Participants (N = 32, Experiment (N = 40, Experiment 2) attempted to exert a pattern of force that resembled in force and time a waveform that was displayed on a computer monitor. In both experiments, the analysis suggested that the GMP, although refined over practice, was relatively stable (i.e., resistant to decay and interference), even early in practice (after 20 trials). In addition, the results indicated that constant and variable parameter practice did not differentially affect GMP learning but did degrade the learning of the parameter that was not varied. The data provided additional evidence for the dissociation of the GMP and the parameterization processes proposed in GMP theory. Contrary to schema theory, the present data suggest an interdependence between the force and the time parameters: The manipulation of 1 of the parameters has a negative effect on the learning of the other parameter.     

Schema Theory: A Critical Appraisal and Reevaluation

The authors replicated and extended results from the gunfight paradigm (A. Welchman, J. Stanley, M. Schomers, R. Miall, & H. Bulthoff, 2010a) in which participants moved faster when reacting to the perceived initiation of an opponent compared to initiating an action themselves. In addition to replicating these movement time effects, the authors found that time to peak velocity, peak velocity, and movement-endpoint dispersions were similarly impacted. The findings are discussed in terms of a triggering mechanism involved in ballistic and internally generated movements.     

Evidence of Common Timing Processes in the Control of Manual,Orofacial, and Speech Movements

Recent investigations of timing in motor control have been interpreted as support for the concept of brain modularity. According to this concept, the brain is organized into functional modules that contain mechanisms responsible for general processes. Keele and colleagues (Keele & Hawkins, 1982; Keele & Ivry, 1987; Keele, Ivry, & Pokorny, 1987; Keele, Pokorny, Corcos, & Ivry, 1985) demonstrated that the within-subject variability in cycle duration of repetitive movements is correlated across finger, forearm, and foot movements, providing evidence in support of a general timing module. The present study examines the notion of timing modularity of speech and nonspeech movements of the oral motor system as well as the manual motor system. Subjects produced repetitive movements with the finger, forearm, and jaw. In addition, a fourth task involved the repetition of a syllable. All tasks were to be produced with a 400-ms cycle duration; target duration was established with a pacing tone, which then was removed. For each task, the within-subject variability of the cycle duration was computed for the unpaced movements over 20 trials. Significant correlations were found between each pair of effectors and tasks. The present results provide evidence that common timing processes are involved not only in movements of the limbs, but also in speech and nonspeech movements of oral structures.     

The Effect of Rest Following Massed Practice of Continuous and Discrete Motor Tasks

Theories of the rest-related phenomena of reminiscence and warm-up decrement regard them as independent, being due to different factors. In this study it was found that rest following massed practice of a continuous task increased performance (reminiscence) and rest following massed practice of a discrete task lowered performance (warm-up decrement). The near-zero correlation found between the phenomena indicates that they are indeed independent and task-specific. Implications of the findings for the prediction of the effect of rest, and the fact that much motor learning and performance is task-specific, is discussed.     

The Timing Effects of Accent Production in Periodic Finger-Tapping Sequences

When subjects are required to produce short sequences of equally paced finger taps and to accentuate one of the taps, the interval preceding the forceful tap is shortened and the one that immediately follows the accent is lengthened. Assuming that the tapping movements are triggered by an internal clock, one explanation attributes the mistiming of the taps to central factors: The momentary rate of the clock is accelerated or decelerated as a function of motor preparation to, respectively, increase or decrease the movement force. This hypothesis predicts that the interre-sponse intervals measured between either tap movement onsets or movement terminations (taps) will show the same timing pattern. A second explanation for the observed interval effects is that the tapping movements are triggered by a regular internal clock but the timing of the successive taps is altered because the forceful movement is completed in less time than the other tap movements are. This “peripheral” hypothesis predicts regular timing of movement onsets but distorted timing of movement terminations. In the present study, the trajectories of the movements performed by subjects were recorded and the interresponse intervals were measured at the beginning and the end of the tapping movements. The results of Experiment 1 showed that neither model can fully explain the interval effects: The fast forceful movements were initiated with an additional delay that took into account the small execution time of these movements. Experiment 2 reproduced this finding and showed that the timing of the onset and contact intervals did not evolve with the repetition of trial blocks. Therefore, the assumption of an internal clock that would trigger the successive movements must be rejected. The results are discussed in the framework of a modified two-stage model in which the internal clock, instead of triggering the tapping movements, provides target time points at which the movements have to produce their meaningful effects, that is, contacts with the response key. The timing distortions are likely to reflect both peripheral and central components.     

Toward a Confucian Notion of Human Dignity

This essay discusses the possibility of conceptualizing a Confucian notion of human dignity. Previous discussions on this topic have been either historical or reconstructive, the former discussing mainly how Confucianism considers dignity and the latter exploring the possibility of conceptualizing a Confucian human dignity as an alternative to Kant’s Menschenwürde. This essay focuses on mainly the latter effort. Specifically, I critically evaluate professor Ni Peimin’s celebrated attempt at reconstructing Confucian dignity in the context of Kant’s Menschenwürde, arguing that Ni’s work offers us novel and original insights on human dignity but fails to be coherent in several senses. On the other hand, Kant’s Menschenwürde may well lack motivation in particular circumstances, and gives no credit to moral efforts. Building upon this criticism, I further Ni’s discussion of the “four hearts” and propose a revised version of Confucian dignity.