Spatial accuracy demand in aiming movements: kinematic analysis of subtended angle and tolerance width

Area of Science:

• Human motor control
• Biomechanics
• Cognitive psychology

Background:

• Subtended angle is traditionally considered crucial for aiming movement programming and kinematics.
• Previous research often used circular targets, where subtended angle covaries with target size (tolerance width).

Purpose of the Study:

• To investigate the independent effects of tolerance width and subtended angle on aiming movements.
• To differentiate the influence of these two factors using multiple target shapes and orientations.

Main Methods:

• Participants performed aiming movements towards targets with varying tolerance widths and subtended angles.
• Movement parameters including reaction time, movement time, and kinematic characteristics were recorded.

Main Results:

• Aiming movements were slower and less efficient when targeting objects with smaller tolerance widths (e.g., vertical rectangle).
• The vertical rectangular target condition showed increased secondary submovements, reduced movement velocity, and higher peak displacement.
• These effects were more pronounced than those related to subtended angle alone.

Conclusions:

• Target tolerance width appears to be a more dominant constraint on aiming movement control than subtended angle.
• Understanding tolerance width is critical for accurately modeling and predicting human aiming movements.