Center or side: biases in selecting grasp points on small bars

Area of Science:

• Neuroscience
• Biomechanics
• Human-Computer Interaction

Background:

• Successful object interaction relies on selecting appropriate grasp points.
• Grasp point selection is influenced by competing factors: stability (center of mass) and movement efficiency (distance).

Purpose of the Study:

• To investigate the interplay between stability and movement minimization in grasp point selection.
• To determine how object properties (mass, friction) and movement parameters affect grasp choices.

Main Methods:

• Participants grasped elongated objects of varying mass and friction from different distances and positions.
• Grasp points were analyzed relative to the object's center of mass and movement origin.
• Experiments included conditions with and without vision, and varying precision requirements.

Main Results:

• Grasping near the center of mass was prioritized, especially for heavy or slippery objects, to prevent rotation.
• A consistent bias towards grasping on the side of the acting hand (right for right-handers) was observed.
• This bias decreased with increased precision demands and was eliminated when movement started above the object.

Conclusions:

• Grasp point selection represents a compromise between stability and a hand-side bias, potentially for enhanced visibility.
• Motor control strategies adapt to object properties and task demands to ensure successful manipulation.