Target dimension affects 1/f noise in aiming.

The present study tested for 1/f noise to examine how timing and target constraints affect cognitive processes in aiming. Participants pointed to targets of varied height and width at preferred speed (Experiment 1) and as quickly as possible (Experiment 2). Results show greater intensity of 1/f noise, or long-range correlation in variability, at preferred speed and with increased accuracy demands perpendicular to the target (i.e., related to height). Prior research suggests that increased 1/f noise in movement reflects increased coordination of processes at different timescales (e.g., planning and control), particularly when there is more time to complete the movement. Previous studies also suggest that target height constraints promote more reliance on both predictive and reactive control, as more time is spent during initial aiming and adjustment. Thus, present results expand on what we know about aiming movements in two ways: (a) by further suggesting a non-orthogonal relation between planning (coarse aiming) and control (fine tuning) that is time dependent; and (b) by demonstrating that such an integration of processes, reflected in distinct patterns of 1/f noise, may be modulated by multiple environmental characteristics (i.e., target shape).