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.

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.