Visual influences on postural and manual interpersonal coordination during a joint precision task.

We investigated whether the interpersonal postural coordination that occurs during a joint supra-postural, manual precision task is driven by the constraints of the task, or, instead results from visual entrainment to the movements of a co-actor. Participants were instructed to coordinate their finger movements under conditions where participants could see others' whole-body movements or could only see the results of the other's actions. Participants' finger and torso movements were recorded. Coordination was quantified using cross-recurrence quantification analysis measures. Interpersonal coordination was enhanced by, although it did not depend entirely upon, visual information about the co-actor's body movements.

Surface shape affects the three-dimensional exploratory movements of nocturnal arboreal snakes.

Movement and searching behaviors at diverse spatial scales are important for understanding how animals interact with their environment. Although the shapes of branches and the voids in arboreal habitats seem likely to affect searching behaviors, their influence is poorly understood. To gain insights into how both environmental structure and the attributes of an animal may affect movement and searching, we compared the three-dimensional exploratory movements of snakes in the dark on two simulated arboreal surfaces (disc and horizontal cylinder). Most of the exploratory movements of snakes in the dark were a small fraction of the distances they could reach while bridging gaps in the light. The snakes extended farther away from the edge of the supporting surface at the ends of the cylinder than from the sides of the cylinder or from any direction from the surface of the disc. The exploratory movements were not random, and the surface shape and three-dimensional directions had significant interactive effects on how the movements were structured in time. Thus, the physical capacity for reaching did not limit the area that was explored, but the shape of the supporting surface and the orientation relative to gravity did create biased searching patterns.

Feedback about isometric force production yields more random variations.

We investigated the relation between visual feedback and the degree of structure versus randomness in the variability of single-digit, isometric force output. Participants were instructed to maintain a constant level of force during the presence or absence of visual feedback about force output. The structure of force output variability was quantified using spectral analysis and detrended fluctuation analysis. Both analyses revealed that force output was less structured (more random) when visual feedback was available than when it was not. More random performance variation seemed to reflect a corrective strategy in the control of action.