A visual perceptual sweet spot for endpoint accuracy judgments during slower actions?

Abstract

When performing rapid voluntary actions (i.e., < 375 ms), brief visual samples provided at approximately 1.0 m/s, prior to peak limb velocity (PV), can yield more accurate endpoint accuracy judgments and online corrections than when provided earlier or later during the limb trajectory (Tremblay et al., 2017). However, it is not known if the optimal window to gather online visual feedback extends to slower actions (cf. sweet spot due to a limited opportunity to utilize online vision during rapid actions). The current study tested for the presence of a perceptual visual sweet spot for slower movements (i.e., 550-650 ms). One of three visual windows of 20 ms was provided when real-time limb velocity reached 0.3, 0.54, or 0.7 m/s, before PV, which were intended to corresponded to comparable proportions of PV than in Tremblay et al. (2017: i.e., approx. 30, 60 and 80% of PV). The results of a forced-choice endpoint judgment task (i.e., undershoot or overshoot) that followed each trial were contrasted with the actual endpoint locations. Using a correlational rank analysis, 55.56% of the participants exhibited their best endpoint bias judgments in the 0.3 m/s (cf. 22.22% participants in each 0.54 and 0.7 m/s window). The results provided some evidence for the generalizability of the sweet spot for slower movements. Also, gathering online visual feedback may take place at an optimal velocity prior to PV (i.e., 30% of PV) during slower movements, at least when making predictions about endpoint accuracy.

Acknowledgments: Natural Sciences and Engineering Research Council of Canada (NSERC), University of Toronto (UofT), Canada Foundation for Innovation (CFI), Ontario Research Fund (ORF).