Visual perception and gaze control in judging versus producing phase relations

Informational constraints on spontaneous visuomotor entrainment

Past research has revealed that an individual's rhythmic limb movements become spontaneously entrained to an environmental rhythm if visual information about the rhythm is available and its frequency is near that of the individual's movements. Research has also demonstrated that if the eyes track an environmental stimulus, the spontaneous entrainment to the rhythm is strengthened. One hypothesis explaining this enhancement of spontaneous entrainment is that the limb movements and eye movements are linked through a neuromuscular coupling or synergy. Another is that eye-tracking facilitates the pick up of important coordinating information. Experiment 1 investigated the first hypothesis by evaluating whether any rhythmic movement of the eyes would facilitate spontaneous entrainment. Experiments 2 and 3 (respectively) explored whether eye-tracking strengthens spontaneous entrainment by allowing the pickup of trajectory direction change information or allowing an increase in the amount of information to be picked-up. Results suggest that the eye-tracking enhancement of spontaneous entrainment is a consequence of increasing the amount of information available to be picked-up.

Observational practice of relative but not absolute motion features in a single-limb multi-joint coordination task

The learning of relative and absolute motion features as a function of physical (actor group) and observational (observer group) practice was examined in a rhythmic single limb multi-joint coordination task. The task required the participants to learn a 90 degrees relative phase pattern between the elbow and wrist in combination with an absolute elbow joint angle of 80 degrees and a wrist joint angle of 48 degrees . Each actor practiced the required relative and absolute motion features for 2 days while being watched by an observer. Overall, the actor group was characterized by an improvement in performance on the relative phase component and showed a clear differentiation in joint amplitudes. In a 24-h retention test, the observer group more closely matched the performance of the actors on the relative phase component in comparison to a control group that was not exposed to physical or observational practice. However, the observer and control groups did not demonstrate a clear differentiation in required joint amplitudes. In agreement with Scully and Newell (1985), we conclude that relative phase may be classified as a relative motion feature that may be picked through observation and benefit initial physical performance, whereas the joint amplitudes may be classified as absolute motion features that require physical practice to achieve the appropriate scaling.

Pattern Stability and Error Correction During In-Phase and Antiphase Four-Ball Juggling

The authors studied pattern stability and error correction during in-phase and antiphase 4-ball fountain juggling. To obtain ball trajectories, they made and digitized high-speed film recordings of 4 highly skilled participants juggling at 3 different heights (and thus different frequencies). From those ball trajectories, the authors determined and analyzed critical events (i.e., toss, zenith, catch, and toss onset) in terms of variability of point estimates of relative phase and temporal correlations. Contrary to common findings on basic instances of rhythmic interlimb coordination, in-phase and antiphase patterns were equally variable (i.e., stable). Consistent with previous findings, however, pattern stability decreased with increasing frequency. In contrast to previous results for 3-ball cascade juggling, negative lag-one correlations for catch-catch intervals were absent, but the authors obtained evidence for error corrections between catches and toss onsets. That finding may have reflected participants' high skill level, which yielded smaller errors that allowed for corrections later in the hand cycle.

1/f (beta) fluctuations in bimanual coordination: an additional challenge for modeling

We analyzed the correlation structure of discrete relative phase (DRP) series in bimanual in-phase and anti-phase coordination by associating a number of fractal methods and using discrete rather than continuous relative phase measurement. ARFIMA/ARMA modeling provided statistical evidence for the presence of long-range correlation, and the series were unambiguously characterized as 1/f (beta) noise. Diverging accounts of bimanual coordination are defended in the literature. Since the evidence for 1/f (beta) noise provides new insight into the properties of stability in coordination, it should be considered as an empirical criterion for determining which mechanisms are likely to be engaged in bimanual coordination models. We discussed some implications for studying the neural basis of coordination, and we tested the performance of three current models in accounting for 1/f (beta) noise in DRP. None of these models was proven to generate the expected correlation structure.