Finger interdependence and unintentional force drifts: Lessons from manipulations of visual feedback

Area of Science:

• Neuroscience
• Motor Control
• Human Factors

Background:

• Unintentional force drift is a phenomenon observed in motor control tasks.
• Existing hypotheses propose drifts originate from individual finger control or coordinated finger modes.

Purpose of the Study:

• To investigate the underlying mechanism of unintentional finger force drift.
• To differentiate between individual finger coordinate drifts and finger mode drifts.

Main Methods:

• Participants performed force production tasks with instructed (master) and non-instructed (enslaved) finger pairs.
• Visual feedback was provided for either master or enslaved finger force, with conditions counterbalanced and blinded.
• Force output of both finger sets was continuously monitored.

Main Results:

• Force drift was observed in both feedback conditions, with subjects unaware of the changes.
• Feedback on master finger force led to an upward drift in enslaved finger force.
• Feedback on enslaved finger force resulted in a downward drift in master finger force.
• Observed drifts could exceed 35% of initial force magnitude.

Conclusions:

• The findings support the hypothesis that force drifts originate from referent coordinate drifts at the individual digit level.
• Evidence does not support the hypothesis of drifts at the level of finger modes.
• The study suggests that quantification of finger enslaving should incorporate brief force production tasks due to observed relative force increases.