Visual and tactile action effects determine bimanual coordination performance

Effect-based models of motor control assign a crucial role to anticipated perceptual feedback in action planning. Two experiments were conducted to test the validity of this proposal for discrete bimanual key press responses. The results revealed that the normally observed performance advantage for the preparation of two responses with homologous rather than non-homologous fingers becomes inverted when homologous fingers produce non-identical visual effects, and non-homologous fingers produce identical visual effects. In the second experiment the finger homology effect was strongly reduced when homologous fingers produced non-identical tactile feedback. The results show that representations of to-be-produced visual and tactile action effects both contribute to action planning, though possibly to a varying degree. Implications of these results for effect-based models of motor control are considered.     

Multitimescale dynamical interactions between speech rhythm and gesture

Temporal patterns in human movement, and in speech in particular, occur on multiple timescales. Regularities in such patterns have been observed between speech gestures, which are relatively quick movements of articulators (e.g., tongue fronting and lip protrusion), and also between rhythmic units (e.g., syllables and metrical feet), which occur more slowly. Previous work has shown that patterns in both domains can be usefully modeled with oscillatory dynamical systems. To investigate how rhythmic and gestural domains interact, an experiment was conducted in which speakers performed a phrase repetition task, and gestural kinematics were recorded using electromagnetic articulometry. Variance in relative timing of gestural movements was correlated with variance in rhythmic timing, indicating that gestural and rhythmic systems interact in the process of planning and producing speech. A model of rhythmic and gestural planning oscillators with multifrequency coupling is presented, which can simulate the observed covariability between rhythmic and gestural timing.     

THE MAGICIAN IN THE WORLD: BECOMING, CREATIVITY, AND TRANSVERSAL COMMUNICATION

This essay interprets the meaning of one of the cards in aTarot deck, "The Magician," in the context of process philosophy in the tradition of Alfred North Whitehead. It brings into the conversation the philosophical legacy of American semiotician Charles Sanders Peirce as well as French poststructuralist Gilles Deleuze. Some of their conceptualizations are explored herein for the purpose of explaining the symbolic function of the Magician in the world. From the perspective of the logic of explanation, the sign of the Magician is an index of nonmechanistic, mutualist or circular, causality that enables self-organization embedded in coordination dynamics. Its action is such as to establish an unorthodox connection crossing over the dualistic gap between mind and matter, science and magic, process and structure, the world without and the world within, subject and object, and human experience and the natural world, thereby overcoming what Whitehead called the paradox of the connectedness of things. The Magician represents a certain quality that acts as a catalytic agent capable of eliciting transmutations, that is, the emergence of novelty. I present a model for process∼structure that uses mathematics on the complex plane and the rules of projective geometry. The corollary is such that the presence of the Magician in the world enables a particular organization of thought that makes pre-cognition possible.     

Cracks in a postdisaster service delivery network

Poor linkage cracks are defined and identified empirically in a postdisaster service delivery network. These cracks exist when essential services are provided only by isolated or peripheral clusters of organizations. Network analysis is used to identify the isolated and peripheral clusters of organizations. Measures of experience in responding to disasters and service capacity are used to identify the organizations whose services are essential in the network. Cracks prevent the network from responding effectively in the aftermath of a disaster. Suggestions are made for using network analysis to identify cracks and to improve planning and coordination in all kinds of service networks. Collection of the data for this work was supported by the National Science Foundation (NSF), Societal Response to Earthquake Hazards Mitigation Program, Grant No. CEE-8314421. The analysis and writing were accomplised with support from the National Science Foundation, Grant No. BCS-8920472. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation. An early version of this paper was presented at the annual meetings of the Midwest Sociological Society, Des Moines, Iowa, April 1991. This paper was distinctly improved through our response to extensive and perceptive suggestions given by the editor and reviewers of theAmerican Journal of Community Psychology. We thank them for the help.     

Effects of physical fatigue and cognitive challenges on the potential for low back injury

There is no question that the motor control system will adapt under fatiguing conditions; however, there is documented evidence showing that when fatigued or challenged, the motor control system will, on occasion, perform inappropriate muscle sequencing, increasing the risk of injury, or directly causing injury. Knowing that inappropriate muscle activations can lead to injury, the purpose of this study was to investigate motor patterns during cognitive and physical challenges. Rather than ensure change with severe challenges, milder challenges were purposefully chosen. Eight male subjects performed a low external load task performed near end ROM while in an unchallenged state, and while in three challenged states: passive tissue creep, muscle fatigue and cognitive distraction. Data were collected using EMG of the trunk muscles and angular displacement of the lumbar spine. Comparison of motor control patterns between the unchallenged state and each of the three challenged conditions showed no systematic differences. However, several random anomalies were observed. A case study of a single subject was chosen to show inappropriate motor control during one trial under the cognitive distraction conditions. The response of the motor control system is very individualized and does on occasion produce inappropriate motor patterns. This supports the notion that injury may also occur as the result of random motor control errors as well as predictable, systematic changes.     

Expanding Echo: Coordinated Head Articulations as Nonmanual Enhancements in Sign Language Phonology

Echo phonology was originally proposed to account for obligatory coordination of manual and mouth articulations observed in several sign languages. However, previous research into the phenomenon lacks clear criteria for which components of movement can or must be copied when the articulators are so different. Nor is there discussion of which nonmanual articulators can echo manual movement. Given the prosodic properties of echoes (coordination of onset/offset and of dynamics such as speed) as well as general motoric coordination of various articulators in the human body, we expect that the mouth is not the only nonmanual articulator involved in echo phonology. In this study, we look at a fixed set of lexical items across 36 sign languages and establish that the head can echo manual movement with respect to timing and to the axis/axes of manual movement. We propose that what matters in echo phonology is the visual percept of temporally coordinated movement that repeats a salient movement property in such a way as to give the visual impression of a copy. Our findings suggest that echoes are not obligatory motor couplings of two or more articulators but may enhance phonological distinctions that are otherwise difficult to see.     

The Dependency Structure of Coordinate Phrases: A Corpus Approach

Hudson (1990) proposes that each conjunct in a coordinate phrase forms dependency relations with heads or dependents outside the coordinate phrase (the “multi-head” view). This proposal is tested through corpus analysis of Wall Street Journal text. For right-branching constituents (such as direct-object NPs), a short-long preference for conjunct ordering is observed; this is predicted by the multi-head view, under the assumption that structures resulting in shorter dependencies are preferred. A short-long preference is also observed for left-branching constituents (such as subject NPs), which is less obviously accommodated by the multi-head view but not incompatible with it. The repetition of determiners was also examined (the dog and cat versus the dog and the cat), and a stronger preference was found for repetition with singular count nouns as opposed to mass or plural nouns; this accords well with the multi-head view, under the reasoning that single-determiner constructions require crossing dependencies with count nouns but not with plural or mass nouns.     

Relationship between fine/gross motor skills and language and math development in Colombian Caribbean children: A study in Barranquilla

Literature suggests that motor skills are associated with other areas of development or domains, such as language and math, especially at early ages. These results are mainly based on studies developed in medium-to-high sociocultural contexts. Thus, this study was conducted in a medium-to-low-income area. The aim was to know the 4–5 years old children's motor development (both fine and gross motor skills), and its relation to language and mathematical development. A total of 219 Colombian Caribbean children (105 boys and 114 girls) aged 4 and 5 years participated in this study. Results revealed higher motor skills among girls, although differences by gender were not notable. Positive and significant correlations were found between motor skills and language and mathematical skills, although most of the correlations were weak or moderate. Also, it was observed that fine motor skills were less related to language or mathematical development in comparison with gross motor skills, especially among boys. These results suggest that among Colombian Caribbean children gross motor skills could have a higher influence on the development and acquisition of some language and mathematical skills in comparison with fine motor skills.     

Lifting weights in neonates: Developing visual control of reaching

To test whether newborn babies take account of external forces in moving their limbs, spontaneous arm-waving movements were measured while the baby lay supine with its head turned to one side. Free-hanging weights, attached to each wrist by strings passing over pulleys, pulled on the arms in the direction of the toes. The results showed the babies applied compensatory forces to keep the hand they faced moving in the same region. In contrast, the (invisible) contra-lateral hand was pulled down by the weights. In a second experiment, where the arms were occluded, both arms were pulled down, suggesting that sight of the arm was necessary in compensating for the weight. In a third, conclusive experiment the babies viewed the arm they were not facing on a small video-monitor and this time the babies kept the visible contra-lateral hand up despite the weights. The results challenge the general view that spontaneous arm movements of neonates are purposeless and either reflexive or due to spontaneous patterned efference to the muscles. Instead, the findings suggest that in waving their arms, neonates are developing visual control of reaching.     

Practice Effects in Bimanual Force Control: Does Age Matter?

ABSTRACT

The authors examined age-related differences in fine motor control during a bimanual coordination task. The task required the modulation of fingertip forces in the precision grip according to a visually presented sinusoidal antiphase pattern (force range 2–12 N; frequency 0.2 Hz). Thirty-four right-handed participants of three age groups (young, early middle-aged, and late middle-aged) practiced 30 trials of the task. Accuracy and variability of relative timing and relative forces at minima and maxima of the sine wave were analyzed for hand–hand and hand–stimulus couplings and compared between age groups. Analysis showed for relative timing and force weaker hand–hand than hand–stimulus coupling as well as lower accuracy and higher variability for minima as compared to maxima. Further, we analyzed practice effects by comparing the first and last trials and characterized the course of practice by detecting the transition of a steeper to a shallower acquisition slope for the different age groups. Late middle-aged participants demonstrated poorer performance than both other groups for all parameters. All groups improved performance to a similar amount. However, an age-related difference in acquisition strategy is visible. Late middle-aged participants seemed to have focused on improvement of force amplitude, whereas young and early middle-aged focused on timing.