Eye-hand coordination during sequential reaching to uncertain targets: the effect of task difficulty, target width,...

Area of Science:

• Human motor control
• Human-computer interaction
• Cognitive neuroscience

Background:

• Fitts' law describes movement time (MT) as a linear function of index of difficulty (ID).
• ID is determined by movement amplitude (A) and target width (W).
• ID influences eye-hand coordination, but previous studies used fixed targets, limiting eye movement analysis.

Purpose of the Study:

• To investigate the impact of index of difficulty (ID) on eye-hand coordination under conditions of target uncertainty.
• To examine how movement amplitude (A) and target width (W) individually affect eye-hand coordination.
• To explore the temporal and spatial trade-offs in eye-hand coordination during reciprocal aiming movements.

Main Methods:

• A modified Fitts' task was used with randomly assigned and unveiled targets.
• Hand and eye movements of 25 participants were recorded.
• Movement amplitude (A) and target width (W) were varied to create different indices of difficulty (ID).

Main Results:

• The linear relationship between movement time (MT) and index of difficulty (ID) persisted despite target uncertainty (R² = 0.99).
• Index of difficulty (ID) continued to impact hand kinematics and eye-hand coordination.
• Eye-hand coordination showed a temporal-spatial trade-off, with greater influence from movement amplitude (A) than target width (W).

Conclusions:

• Task difficulty (ID) critically influences eye-hand coordination, even with unpredictable targets.
• Eye-hand coordination involves a trade-off between temporal and spatial adjustments.
• Movement amplitude (A) plays a more significant role than target width (W) in eye-hand coordination, highlighting potential task scaling effects.