The Impact of Strategic Trajectory Optimization on Illusory Target Biases During Goal-Directed Aiming

ABSTRACT

During rapid aiming, movements are planned and executed to avoid worst-case outcomes that require time and energy to correct. As such, downward movements initially undershoot the target to avoid corrections against gravity. Illusory target context can also impact aiming bias. Here, the authors sought to determine how strategic biases mediate illusory biases. Participants aimed to Müller-Lyer figures in different directions (forward, backward, up, down). Downward biases emerged late in the movement and illusory biases emerged from peak velocity. The illusory effects were greater for downward movements at terminal endpoint. These results indicate that strategic biases interact with the limb-target control processes associated with illusory biases. Thus, multiple control processes during rapid aiming may combine and later affect endpoint accuracy (D. Elliott et al., 2010).

Keywords:

• aiming
• limb-target control
• movement optimization
• multiple process model

ACKNOWLEDGMENTS

We would like to thank Dave Burkitt for his technical support.

Funding

This project was funded by the Natural Sciences and Engineering Research Council (NSERC) of Canada.

Notes

1. Previous work has shown that similar movement environments featuring visual feedback of the limb typically elicits a robust Müller-Lyer effect (e.g., Mendoza et al., 2006).

2. Though we recognize the backward aims indicate equally greater illusory biases compared to upward and forward aims, the shorter time and displacement in the secondary submovement (limb-target control) suggests it unfolded for very different reasons. We speculate the backward aims may have garnered a predominantly allocentric frame of reference following movement directed toward the performer's space (Forsyth, Puckering, & Bryden, 2015).