Quiet eye and motor performance: Testing the "optimal duration" hypothesis

Particularly in targeting tasks, the final fixation before movement initiation (Quiet Eye, QE) reliably predicts motor performance (Vickers, 2016). In this regard, an optimal QE-performance relation has been assumed (e.g., Behan & Wilson, 2008), meaning short and very long QE durations deteriorate performance. This hypothesis was put to empirical practice by testing throwing accuracy as a function of short, long, and very long QE-duration conditions. In addition, QE-performance curve fittings were conducted to assess the actual relation between those variables. In each of two experiments, 22 sport-science students threw balls as accurate as possible at virtually target disks that were displayed at 8 different moments in time before movement initiation (ranging from 400 ms to 3200 ms). Throwing performance and gaze behavior were assessed with a 10-camera VICON system (200 Hz) and an integrated eye-tracking system (EyeSeeCam, 220 Hz). Radial error (mm) and QE duration (ms) were calculated as dependent measures. For the curve fittings, the actual data for each participant were individually fitted to linear, quadratic and decayed exponential functions.
While the results showed a successful QE manipulation in relative values, particularly in the very long QE-duration conditions the intended QE durations were not reached. For throwing performance, less accurate throws were found in short (M = 165 mm) vs. long (M = 140 mm) but no further performance differences in very long QE-duration conditions. Likewise, the curve fittings revealed performance improvements until 2000 ms but no further notably performance differences until 4000 ms. The results emphasize the mutual coupling between perception and action as the demands of the motor task restricted the intended QE maximization. Furthermore, the relation between the QE and performance seems to be best described by an exponential decay that rather supports a response-programming function of the QE (Gonzales et al., 2015). Further theoretical considerations and the transfer into practice will be discussed.