Piet C.W. van Wieringen

Phase transitions in rhythmic tracking movements : a case of unilateral coupling

Abstract Previous research has demonstrated that both within and between persons two limbs coordinated in an anti-phase mode (relative phase of 180 degrees) spontaneously switch to an in-phase mode (relative phase of 0 degrees) when movement frequency is increased. These phase transitions satisfy the criteria of physical bifurcations. The present experiments generalize this finding to movements of a single limb (lower arm) coordinated with the motion of an externally driven visual signal. The results support the idea that phase transitions in coordinated rhythmic movements are due to the presence of informational resolution limitations of the system, and are therefore to be understood as ‘threshold non-linearities’. Once in a particular behavioural mode a threshold is reached due to changes in a system parameter, a phase transition occurs if, and only if, there is another behavioural mode available under which the global task goals can be satisfied at lower informational costs. If the spatial conditions of the task are manipulated in such a way that the relation between the information specifying the behaviour and the information generated by the behaviour is identical for both behavioural modes (in-phase, anti-phase), no phase transitions occur.

Gait coordination after stroke: Benefits of acoustically paced treadmill walking

Background and Purpose: Gait coordination often is compromised after stroke. The purpose of this study was to evaluate the efficacy of acoustically paced treadmill walking as a method for improving gait coordination in people after stroke. Participants: Ten people after stroke volunteered for the study and comprised the experimental group. Nine elderly people who were healthy served as a control group. Methods: Gait cycle parameters, interlimb coordination, and auditory-motor coordination were examined while participants walked on a treadmill with and without acoustic pacing. Results: Stride frequency was adjusted to different acoustic pacing frequencies in all participants. In people after stroke, gait symmetry improved with acoustic pacing. They predominantly coordinated movements of the nonparetic limb to ipsilateral tones. Discussion and Conclusion: The results suggest that acoustically paced treadmill walking provides an effective means for immediately modifying stride frequency and improving gait coordination in people after stroke and, therefore, may be usefully applied in physical therapist practice. Future research directions for developing guidelines for using acoustically paced treadmill walking in physical therapist practice are discussed.

Beauty in the eye of expert and nonexpert beholders : A study in the appraisal of art

In this study, professional art experts and nonexperts with an active interest in art rated sets of 10-20 slides of artworks made available by young artists. Each set was rated on bipolar scales, including not original-original; absence of crafts-manship-craftsmanship; and poor quality-good quality. Intraclass coefficients R i for these three scales were .17, .21, and .22 for experts and .19, .08, and .16 for nonexperts, respectively. There was a significant agreement between experts and nonexperts with respect to originality, but no agreement with respect to craftsmanship and quality. The correlation between originality and quality was significantly (p <.01) higher for experts (r.88) than for nonexperts (r=.40). Thus, experts seem to attach much more value to originality in determining aesthetic quality than nonexperts.

Frequency-induced phase transitions in bimanual tapping

The stability of bimanual performance of the frequency ratios 3∶8 and 5∶8 was examined from the perspective of the sine circle map and the associated Farey mode-locking hierarchy. By gradually increasing movement frequency, abrupt transitions from the initial frequency ratios to other frequency ratios were induced. In general, transitions occurred to frequency ratios that were near the initial frequency ratio but lower in the Farey ordering and, hence, of higher stability in the sine circle map. A fair percentage of these transitions were to unimodularly related ratios. The transition routes from 3∶8 and 5∶8 remained largely unaffected by extensive practice of the lower-order ratios 2∶5 and 3∶5. Collectively, these results suggest that (i) bimanual tapping occurs in a domain in which frequency-locked states either overlap or are located sufficiently close to each other to make stochastic switching possible (coupling parameter K > 1 or close to 1); (ii) the overall stability of these frequency-locked states decreases as movement frequency increases (due to a decrease in K) and, consequently, (iii) the probability of transitions to nearby frequency ratios increases as movement frequency increases, due to the differential stability of the frequency locks.

Limit cycle properties of rhythmic forearm movements.

The kinematics of 1and 2-armed rhythmic forearm movements were examined using the methodology and limit cycle modeling strategy of B. A. Kay, J. A. S. Kelso, E. L. Saltzman, and G, Schoner (1987). As frequency was paced from 1 to 6 Hz (in steps of 1 Hz), amplitude decreased in all 7 participants, whereas peak velocity showed different trends for different participants. The data of 2 of the 7 participants could be described with Kay et al.s model. To account for the data of the remaining 5 participants, a new model was proposed with a dissipative structure involving a frequency-dependent Rayleigh term and a standard Van der Pol term. For 2 of these 5 participants, the coefficient of the Van der Pol term was not significantly different from zero. Contrary to Kay et al.s model, the new model suggests that the energy bookkeeping of rhythmic forearm oscillations is affected by the frequency of movement.

The impact of level of expertise on the evaluation of original and altered versions of post-impressionistic paintings

Abstract Twelve post-impressionistic paintings were manipulated along two dimensions: degree of realism (figurative vs. abstract) and colour (colour vs. black-and-white). The resulting 48 pictures were rated by three groups of twenty subjects each, on a number of rating scales. The three groups differed as to their expertise in art. Analyses of variance on the mean liking scores indicated that the negative effects of changing the original pictures to abstract or black-and-white versions decreased with increasing expertise. This differential impact of the experimental manipulations confirmed hypotheses about changes in taste due to artistic training.

Gross motor performance and physical fitness in children with psychiatric disorders

Aim  Gross motor performance appears to be impaired in children with psychiatric disorders but little is known about which skill domains are affected in each disorder, nor about possible accompanying deficits in physical fitness. The present study has sought to provide information about these issues in children with emotional, behavioural, and pervasive developmental disorders (PDD).

Spatio-temporal organisation of natural prehension ☆

Bootsma, R.J. and P.C.W. van Wieringen, 1992. Spatio-temporal organisation of natural prehension. Human Movement Science 11, 205-215. An information-based model of natural prehension is proposed that can account for a large number of experimental findings without taking recourse to prestructured movement plans. It is suggested that coordination of the transport and grasping components is guaranteed because both components are ultimately geared to the same information specifying time-to-contact between the hand and the object to be grasped, and that therefore no special control structures responsible for this coordination are required.

The Effect of Verbal Instruction and Artistic Background on the Aesthetic Judgment of Rectangles

A review of studies on the judgment of rectangle proportions pointed out that individual differences in preference might be partly due to differences in verbal instructions given to the subjects. In the present experiment two types of instruction were used and their effects on both naive and experienced (art school) subjects were assessed. Following a subjective instruction, emphasizing personal preference, mean ratings of naive subjects revealed a preference peak around the Golden Section, whereas mean ratings of experienced viewers peaked at the square. In the objective condition, involving judgment of the goodness of proportion regardless of personal liking, the mean preferences of both groups clearly tended toward the square. Individual preference functions partly confirmed these mean patterns, but demonstrated large intersubject variability. Moreover, the naive viewers were significantly more consistent in their ratings than the experienced ones.

Perspectives on the relation between information and dynamics: An epilogue

Abstract In this epilogue to the special issue of Human Movement Science on the role of information in dynamical accounts of action, three broadly defined approaches are distinguished, namely the ecological approach formulated by Gibson, the perception-action approach formulated by Kugler and Turvey and the dynamical approach formulated by Kelso and Schoner. These three approaches serve as a framework for discussing the various contributions to the special issue, which address current conceptual problems in connecting information and dynamics and propose novel ways to solve them.