Interactions between goal-directed eye and arm movements: arguments for an interdependent motor control

The accuracy of movements of the arm directed toward a point in space was investigated in healthy human subjects. To study the influence of the eye movement itself, on the guidance of the arm in the absence of any visual context, subjects performed the goal-directed arm movements without visual feedback about the arm displacement and the target position. The subjects were asked either to keep their eyes centered or oriented toward a previously flashed target. The analysis of the distribution of the errors in arm final position in the two conditions suggests that the eye movement influences the final position adopted by the arm. It is postulated that an interaction exists between the eye and arm systems during the motor program elaboration phase.     

Hemispheric asymmetries in attentional control: implications for hand preference in sensorimotor tasks

Liepmann (1908) proposed that handedness reflects the greater capacity of one hemisphere to learn the execution of skilled movements. Although asymmetries in motor control are an important basis for hand asymmetries, recent studies have suggested that handedness may be determined by multiple factors. In the present study, we examine how attentional asymmetries may contribute to hand preferences. Right-handed subjects participated in a reaction time task in which they were given preliminary information about where a target stimulus would occur (selective attention) or which hand to use for responding (selective intention). Our findings indicate that these processes influence each other reciprocally and favor a state of optimal attentional and intentional preparation of the right hand. We suggest that these hemispheric asymmetries in attentional control contribute to hand preferences in certain sensorimotor tasks.     

Fast aiming movements with the left and right arm: Evidence for two-process theories of motor control

Summary The kinematics of leftward and rightward movements are different. The question is raised whether these differences in both arms are best accounted for in terms of the flexion-extension dimension or the leftward-rightward dimension. In a simple step-tracking experiment the acceleration-time curves of fast flexions and extensions of the left and of the right elbow joint in a horizontal plane were recorded. The durations of individual segments of the acceleration curves are best predicted by spatial direction: that is, the differences between leftward and rightward movements are either both positive or both negative in both arms. This holds only for the first part of the movement until maximum deceleration is reached. From then on the timing is best predicted by the flexion-extension dimension. This is taken as evidence for a two-process theory of motor control according to which a central process is first in command and a lower-level, muscle-related process then takes over. Although a change which corresponds to the one observed in the time variables is not seen in the maxima of the acceleration curves, this seeming disparity can be reconciled with a two-process theory.     

Language learning and innateness: some implications of Compounds Research

In noun compounds in English, the modifying noun may be singular (mouse-eater) or an irregularly inflected plural (mice-eater), but regularly inflected plurals are dispreferred (*rats-eater). This phenomenon has been taken as strong evidence for dual-mechanism theories of lexical representations, which hold that regular (rule-governed) and irregular (exception) items are generated by qualitatively different and innately specified mechanisms. Using corpus analyses, behavioral studies, and computational modeling, we show that the rule-versus-exceptions approach makes a number of incorrect predictions. We propose a new account in which the acceptability of modifiers is determined by a constraint satisfaction process modulated by semantic, phonological, and other factors. The constraints are acquired by the child via general purpose learning algorithms, based on noun compounds and other constructions in the input. The account obviates the regular/irregular dichotomy while simultaneously providing a superior account of the data.     

Counselling and psychotherapy as a form of learning: some implications for practice

This paper explores counselling and psychotherapy as a form of learning. Previous experiences may create distortions in meaning-making perspectives, distortions that create templates for evaluating future experience. These templates act as barriers to being open to experience; thus there is an inability to learn from experience. The process of therapy can provide a learning milieu for the exploration and working through of these barriers, with a potential outcome of a return to learning from experience. It is suggested here that intrinsic to the learning milieu created in therapy there are elements of significant, transformative and emotional learning. Therapy is thus a reparative discourse that facilitates a return to learning from experience. A deconstruction of this concept is provided here as a way of developing the exploration of counselling and psychotherapy as a form of learning.     

Posture control and complex arm coordination: analysis of multijoint coordinative movements and stability of stance

The authors addressed the interactions between control of bimanual multijoint coordination tasks and posture. Participants (N = 6) performed 8 coordination patterns that differed in degree of complexity by using their bilateral elbows and wrists under 3 scaled motion speeds while standing on 2 force plates. Results indicated that producing complex bimanual multijoint coordinative tasks affected postural sway, thus resulting in an increase of sway activity. Behavioral as well as mechanical factors accounted for the increased disturbance in postural sway. Those findings suggest that performing complex coordination tasks disrupts postural control in normal young adults.     

Mental representations of magnitude and order: A dissociation by sensorimotor learning

Numbers and spatially directed actions share cognitive representations. This assertion is derived from studies that have demonstrated that the processing of small- and large-magnitude numbers facilitates motor behaviors that are directed to the left and right, respectively. However, little is known about the role of sensorimotor learning for such number–action associations. In this study, we show that sensorimotor learning in a serial reaction-time task can modify the associations between number magnitudes and spatially directed movements. Experiments 1 and 3 revealed that this effect is present only for the learned sequence and does not transfer to a novel unpracticed sequence. Experiments 2 and 4 showed that the modification of stimulus–action associations by sensorimotor learning does not occur for other sets of ordered stimuli such as letters of the alphabet. These results strongly suggest that numbers and actions share a common magnitude representation that differs from the common order representation shared by letters and spatially directed actions. Only the magnitude representation, but not the order representation, can be modified episodically by sensorimotor learning.     

Computergraphic modeling and analysis: A portable system for tracking arm movements in three-dimensional space

A system is presented that allows automated, three-dimensional tracking of hand and arm movements. The system incorporates commercially available optoelectronic cameras and provides portable and affordable, yet accurate, three-dimensional monitoring of multiple joints of the hands and arms. Special-purpose hardware components were developed, as was software for data acquisition, data processing, and graphic display. The hardware and software are described, along with such necessary procedures as system calibration and transformation of coordinate system frames of reference. Testing of the system revealed highly accurate three-dimensional spatial tracking. The three-dimensional numeric and graphic analyses of movement made possible by this system allow new studies into the nature of the neural control of movement.     

From movements to actions: two mechanisms for learning action sequences

When other individuals move, we interpret their movements as discrete, hierarchically-organized, goal-directed actions. However, the mechanisms that integrate visible movement features into actions are poorly understood. Here, we consider two sequence learning mechanisms – transitional probability-based (TP) and position-based encoding computations – that have been studied extensively in the domain of language learning, and investigate their potential for integrating movements into actions. If these learning mechanisms integrate movements into actions, then they should create memory units that contain (i) movement information, (ii) information about the order in which movements occurred, and (iii) information allowing actions to be recognized from different viewpoints. We show that both mechanisms retain movement information. However, only the position-based mechanism creates movement representations that are view-invariant and contain order information. The TP-based mechanism creates movement representations that are view-dependent and contain no order information. We therefore suggest that the TP-based mechanism is unlikely to play an important role for integrating movements into actions. In contrast, the position-based mechanism retains some of the types of information needed to represent goal-directed actions, which makes it an attractive target for further research to explore what, if any, role it plays in the perception of goal-directed actions.     

Modularity for sensorimotor control: evidence and a new prediction

By combining a few modules, the CNS may learn new control policies quickly and efficiently. Support for a modular organization of the motor system has recently come from the observation of low dimensionality in the motor commands. However, stronger evidence would come from testing the predictions on the effect of an intervention on the mechanisms required to implement a modular controller. Thus, the authors propose to test the predictions of modularity on motor adaptation. They argue that unlike a nonmodular controller, a modular controller must adapt faster to a perturbation that is compatible with the modules (i.e., one that can be compensated by reusing the same modules), than to an incompatible perturbation (i.e., one that requires new modules).     

Application of a model to paired-associate learning

The proposal is made to consider a paired-associate item as becoming conditioned to its correct response in all-or-none fashion, and that prior to this conditioning event the subject guesses responses at random to an unlearned item. These simple assumptions enable the derivation of an extensive number of predictions about paired-associate learning. The predictions compare very favorably with the results of an experiment discussed below.This research was supported by a grant, M-3849, from the National Institutes of Mental Health, United States Public Health Service.     

Latency of sequential eye movements: implications for reading

The best available estimates indicate that the average minimum latency of saccadic eye movements (175-200 msec) approaches the mean duration of fixations in reading (200-250 msec). This fact presents a problem for models of reading which assume that an eye movement is initiated only after substantial information is processed on a fixation. Three experiments are reported that support earlier estimates of saccadic latency; the experiments were conducted under conditions in which the length of measured latencies could not reflect a motoric refractory period, spatial uncertainty, or temporal uncertainty.     

A psychological model of social control and stigmatization: evolutionary background and practical implications

The strengths and limitations of three main theoretical approaches to social control and stigmatization are discussed, originating from social psychology, sociology and anthropology, and evolutionary psychology, respectively. A theoretical model is proposed that integrates universal (evolutionary derived) psychological aspects of social control and the great variation that can be observed in responding to deviance within and between cultures and historical periods. Practical implications of the model are discussed.     

Mapping sensorimotor sequences to word sequences: A connectionist model of language acquisition and sentence generation

In this article we present a neural network model of sentence generation. The network has both technical and conceptual innovations. Its main technical novelty is in its semantic representations: the messages which form the input to the network are structured as sequences, so that message elements are delivered to the network one at a time. Rather than learning to linearise a static semantic representation as a sequence of words, our network rehearses a sequence of semantic signals, and learns to generate words from selected signals. Conceptually, the network's use of rehearsed sequences of semantic signals is motivated by work in embodied cognition, which posits that the structure of semantic representations has its origin in the serial structure of sensorimotor processing. The rich sequential structure of the network's semantic inputs also allows it to incorporate certain Chomskyan ideas about innate syntactic knowledge and parameter-setting, as well as a more empiricist account of the acquisition of idiomatic syntactic constructions.     

The response to domestic violence in a model court: some initial findings and implications

This study utilized a non-experimental design to obtain information on a full range of domestic violence incidents brought before the Quincy, Massachusetts District Court, a model court. One limitation of previous research on spouse assaults using more sophisticated designs is that the target population has been restricted to specific subgroups of cases thereby limiting subsequent discussions of policy/practice implications of the findings vis-a-vis all spouse assault cases. To address this research “shortfall”, we obtained permission from the Quincy District Court to examine all the spouse assault cases brought before the court during a 7-month period (June, 1995, through February, 1996). The findings show that in a full enforcement environment, victims took out restraining orders only against the most violent, criminally abusive men. Most men who were arrested for domestic violence had prior criminal histories for a variety of offenses. Domestic violence offenders appeared to be of two types: those with extensive and diverse criminal histories and those with little or no such involvement. However, active criminal justice intervention against domestic violence offenders appears to be primarily directed toward offenders already active in the criminal justice system. © 1998 John Wiley & Sons, Ltd.     

Application of the new method for the Rescorla-Wagner model to a probabilistic learning situation

The author recently showed that it is not always necessary to perform simulations to derive predictions from the Rescorla-Wagner model, and presented an alternative method. In this article, the method is applied to an influential experimental paradigm: base-rate neglect.     

A case study of mediated learning, delayed auditory feedback, and motor repatterning to reduce stuttering

A case study of DW, an 11-yr. old monolingual, English-speaking boy who exhibits stuttering, language delay, and ADHD is presented. DW experienced only limited improvement during stuttering therapy received in public schools, according to parents and the public school clinician. The purpose of this case study was to assess whether fluency treatment which incorporated Mediated Learning, Delayed Auditory Feedback, and Speech Motor Repatterning would enhance progress. Therapy was delivered in two treatments, with each treatment being 5 wk. of intense therapy, separated by one year. Treatment 1 of combined Mediated Learning and Delayed Auditory Feedback yielded improvement in fluency, judged by parents and the teacher to be clinically significant. The improved fluency was maintained for one year when DW was pretested for participation in Treatment 2, which combined Mediated Learning, Delayed Auditory Feedback, and Speech Motor Repatterning Exercises. As no conclusions are possible, further study is needed.