Multi-person and multisensory synchronization during group dancing

Synchronized group dancing is one of the hallmarks of both coordination and cooperation in the humans species. While a large amount of research has focused on joint action in dyads, the mechanisms of coordination in larger groups are not well understood. In the present study, we explored the coordination dynamics of a group of folk dancers by examining the influence of three sensory-coupling channels on the stability of group coordination. Using 3D motion capture, we recorded a group of 13 expert folk dancers performing to the beat of music (auditory coupling) while holding hands in a circle (haptic coupling) and seeing their fellow dancers (visual coupling). Analyses of group synchrony using cluster phase analysis demonstrated that selective elimination of any one of the three types of sensory coupling significantly reduced group synchrony, where haptic coupling had the strongest effect on movements in the horizontal plane, but also impacted the vertical axis. This study provides some of the first evidence of how sensory couplings support multi-person coordination in a large group, and in particular the effect of body contact on this coordination.     

Effects of arm weight on C-not-B task performance: implications for the motor inhibitory deficit account of search failures

Toddlers have been found to fail on a three-location search task involving the invisible displacements of an object, namely the C-not-B task. In this task, a child is shown the experimenter's hand that contains a toy. The toy then successively disappears under the three cloths (A, B, then C). The examiner silently releases the toy under the second cloth (B). The hidden object makes a bump in the B cloth that covers it. Young children emit a strong bias toward the last cloth that the experimenter's hand passes under, and this has been labeled the C-not-B error. One possible explanation for toddlers' failures in the C-not-B task is that children lack the motor inhibitory mechanisms. To test this hypothesis, the robustness of the C-not-B error was tested, in a first experiment, against variations in body parameters. By putting additional weights on the arm, the C-not-B error was reduced substantially and the C-not-B task had a higher rate of success. Indeed, in contrast to control participants, who ignored a visual clue indicating the correct location of the hidden object and reached for the last location of the experimenter's hand, the participants with arm weights initiated their reaching movements by using the visual clue. The findings from the second control group indicate that the dramatic increase in successful performance by children with arm weights is not merely a consequence of the focus on the attention to arm movements. The motion of the experimenter's hand in space appears to have made the task difficult because toddlers had no problems inferring that a lump under a cloth indicates the existence of an object without actually having watched an object be hidden there, as demonstrated in a second experiment. The findings are consistent with the hypothesis that C-not-B task content activates a prepotent motor response that preempts full consideration of a visual clue indicating the correct location of the hidden object. We propose that the success in the C-not-B task of toddlers with additional arm weights could result from a disruption of automatic hand movement that is triggered by sensory signals, namely salient features of the C-not-B task.     

Gaze behaviors of goaltenders under spatial-temporal constraints

It is still not known what underlies successful performance in goaltending. Some studies have reported that advanced cues from the shooter's body (hip, kicking leg or support leg) are most important (Savelsbergh, G. J. P., Williams, A. M., Van der Kamp, J., & Ward, P. (2002). Visual search, anticipation and expertise in soccer goalkeepers. Journal of Sports Sciences, 20, 279-287; Savelsbergh, G. J. P., Williams, A. M., Van der Kamp, J., & Ward, P. (2005). Anticipation and visual search behaviour in expert soccer goalkeepers. Ergonomics, 48, 1686-1697; Williams, A. M., & Burwitz, L. (1993). Advanced cue utilization in soccer. In T. Reilly, J. Clarys, & A. Stibbe (Eds.), Science and football II (pp. 239-243). London, England: E&FN Spon), while others have found that the early tracking of the object prior to and during flight is most critical (Bard, C., & Fleury, M. (1981). Considering eye movement as a predictor of attainment. In: I. M. Cockerill, & W. M. MacGillvary (Eds.), Vision and Sport (pp. 28-41). Cheltenham, England: Stanley Thornes (Publishers) Ltd.). These results are similar to those found in a number of interceptive timing studies (Land, M. F., & McLeod, P. (2000). From eye movements to actions: How batsmen hit the ball. Nature Neuroscience, 3, 1340-1345; Ripoll and Fleurance, 1988; Vickers, J. N., & Adolphe, R. M. (1997). Gaze behaviour during a ball tracking and aiming skill. International Journal of Sports Vision, 4, 18-27). The coupled gaze and motor behavior of elite goaltenders were determined while responding to wrist shots taken from 5 m and 10 m on ice. The results showed that the goalies faced shots that were significantly different in phase durations due to distance (5 versus 10 m), but this was not a factor in making saves. Instead, the ability to stop the puck was dependent on the location, onset and duration of the final fixation/tracking gaze (or quiet eye) prior to initiating the saving action. The relative onset of quiet eye was significantly (p<.001) earlier (8.6%) and the duration was longer on saves (M=80.5%; 952.3 ms) compared to goals (onset 18.86%; M=70.1%, 826.1 ms). The quiet eye was located on the puck/stick during the preparation and execution of the shot in 70.53% of all trials, or on the ice in front of the release point of the puck (25.68%) and rarely on the body of the shooter (2.1%). The results are discussed within the context of current research on goaltending with specific emphasis on the timing of critical cues and the effect of tasks constraints.     

Sensory information affords exploration of posture in newly walking infants and toddlers

The development of posture and locomotion provides a valuable window for understanding the ontogeny of perception-action relations. In this study, 13 infants were examined cross-sectionally while standing quietly either hands-free or while lightly touching a contact surface. Mean sway amplitude results indicate that infants use light touch for sway attenuation (≈28–40%) as has been seen previously with adults (Jeka & Lackner, 1994). Additionally, while using the contact surface, movement patterns of the head and trunk show reduced temporal coordination (≈25–40%), as well as increased temporal variability, as compared to no touch conditions. These findings are discussed with regard to the ontogeny of perception-action relations, with the overall conclusion that infants use somatosensory information in an exploratory manner to aid in the development of an accurate internal model of upright postural control.     

Leg Asymmetries and Coordination Dynamics in Walking

Models of interlimb coordination (H. Haken, J. A. S. Kelso, &; H. Bunz, 1985 Haken, H., Kelso, J. A. S. and Bunz, H. 1985. A theoretical model of phase transitions in human hand movements. Biological Cybernetics, 51: 347–356. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; P. N. Kugler &; M. T. Turvey, 1987 Kugler, P. N. and Turvey, M. T. 1987. Information, natural law, and the self-assembly of rhythmic movement, Hillsdale, NJ: Erlbaum.  [Google Scholar]) were tested in walking by examining the role of asymmetries between limbs. Participants walked on a treadmill with and without a metronome. Five asymmetry conditions were created via ankle loads of 0, 3, or 6 kg on either leg. With the metronome, participants matched the target period. Without the metronome, stride rate slowed as the mass was increased on either leg. The loads led to an increase in stride period that was predicted by Huygens’ law and the hybrid pendulum-spring model. In agreement with extended Haken–Kelso–Bunz model predictions, leg asymmetries led to deviations from antiphase coordination. Also, perception–action coordination was influenced by the asymmetry between the legs and metronome. In contrast, no predicted stability effects were observed. These findings reveal that some properties of interlimb coordination, apparent in laboratory-based tasks, can also be observed in human walking.     

Coordination Between Arm and Leg Movements During Locomotion

To evaluate the contrasting dynamical and biomechanical interpretations of the 2:1 frequency coordination between arm and leg movements that occurs at low walking velocities and the 1:1 frequency coordination that occurs at higher walking velocities, the authors conducted an experiment in which they quantified the effect of walking velocity on the stability of the frequency and phase coordination between the individual limb movements. Spectral analyses revealed the presence of 2:1 frequency coordination as a consistent feature of the data in only 3 out of 8 participants at walking velocities ranging from 1.0 to 2.0 km/h, in spite of the fact that the eigenfrequencies of the arms were rather similar across participants. The degree of interlimb coupling, as indexed by weighted coherence and variability of relative phase, was lower for the arm movements and for ipsilateral and diagonal combinations of arm and leg movements than for the leg movements. Furthermore, the coupling between all pairs of limb movements was found to increase with walking velocity, whereas no clear signs were observed that the switches from 2:1 to 1:1 frequency coordination and vice versa were preceded by loss of stability. Therefore, neither a purely biomechanical nor a purely dynamical model is optimally suited to explain these results. Instead, an integrative model involving elements of both approaches seems to be required.     

Bimanual coupling effects during arm immobilization and passive movements

When humans simultaneously perform different movements with both hands, each limb movement interferes with the contralateral limb movement (bimanual coupling). Previous studies on both healthy volunteers and patients with central or peripheral nervous lesions suggested that such motor constraints are tightly linked to intentional motor programs, rather than to movement execution. Here, we aim to investigate this phenomenon, by using a circles-lines task in which, when subjects simultaneously draw lines with the right hand and circles with the left hand, both the trajectories tend to become ovals (bimanual coupling effect). In a first group, we immobilized the subjects’ left arm with a cast and asked them to try to perform the bimanual task. In a second group, we passively moved the subjects’ left arm and asked them to perform voluntary movements with their right arm only. If the bimanual coupling arises from motor intention and planning rather than spatial movements, we would expect different results in the two groups. In the Blocked group, where motor intentionality was required but movements in space were prevented by immobilization of the arm, a significant coupling effect (i.e., a significant increase of the ovalization index for the right hand lines) was found. On the contrary, in the Passive group, where movements in space were present but motor intentionality was not required, no significant coupling effect was observed. Our results confirmed, in healthy subjects, the central role of the intentional and predictive operations, already evidenced in pathological conditions, for the occurrence of bimanual coupling.     

The effect of preview eccentricity in a lexical decision task

We report lexical decision experiments in which eye movements and lexical decision time were analysed. The results show that nonwords produced more fixation than words, and that the time to make a lexical decision was also greater for nonwords. Further, a preview of the stimulus was presented on some occasions either at fixation or peripherally. When the presentation was peripheral the number of refixations and lexical decision times were reduced. Parafoveal previews of words also reduced word length effects on refixations and lexical decision time. These effects decreased (for nonwords) when the case of the letters was changed in the preview. These results are compatible with the idea that the peripheral preview benefit derives from word visual structure in addition to information about word length, word envelope, and single letter identities.     

伸手拦截启动中的信息利用

通过两项实验考察时空信息对拦截运动启动的影响: 实验一为知觉估计实验, 通过释放匀速小球模拟拦截过程; 实验二为特定拦截路线情景下的拦截行为实验, 即固定手的拦截方向, 但容许拦截速度自由控制。结果发现, 拦截行为的启动基于综合信息, 在所拦截物体作慢速运动的情景下拦截行为启动偏早, 而在快速运动的情景下启动偏晚, 结果不支持单纯用tau理论解释启动行为。本研究对手的速度伴随效应提出了新的解释。     

When the going gets tough,what happens to quiet eye? The role of time pressure and performance pressure during basketball free throws

In aiming sport contexts, the quiet eye (QE) - the final ocular fixation before movement initiation - is a crucial perceptual-cognitive skill. Indeed, an extended QE permits athletes to achieve high performances, aiding optimal attentional control, particularly in situations in which athletes are "under pressure." Such situations are common in sport, especially when time runs out, and even just a few points can mean the difference between victory and defeat. Although QE has been widely investigated across several sports and tasks, no previous studies have considered both the role of time pressure and performance pressure on QE. The current study aimed to comprehend the effect of tough sport situations on QE characteristics. Accordingly, we tested basketball players (competitive-élites and semi-élites) in free throw trials, manipulating both the time available to perform the task and the relevance of the performance. The results showed that time pressure and performance pressure impaired QE characteristics, regardless of expertise levels. Also, time pressure led to a decrease in free throw accuracy. Interestingly, the match between task demands and the ability to cope seemed to play a role on QE, especially in the competitive-élite players, with negative QE characteristics (short and late) when task demands exceeded the ability to cope. These findings suggest that QE research and QE training protocols should account for time pressure, performance pressure, and the players' perceived ability to cope with the requested task.