Abstract
Predictive eye movements targeted towards the direction of ball-bounce are a feature of gaze behavior when intercepting a target soon after it has bounced (Land & McLeod, 2000). However, there is conjecture over the strategy that is used when generating these predictions and why they would be necessary. In particular, some studies have reported that gaze as a result of those predictions ‘lies-in-wait’ for the ball at the location of bounce (Land & McLeod, 2000; Mann, Spratford & Abernethy, 2013) whereas other studies suggest that exquisite predictions are made to relocate gaze towards where the ball will be at some point following bounce (Diaz, Cooper, Rothkopf & Hayhoe, 2013). The aim of this study was to better understand the nature of the predictive eye movements that are made when hitting a bouncing ball. We tracked the eye and head movements of 23 novice participants who attempted to hit approaching tennis balls that bounced at different distances from them in a virtual environment. Results revealed that participants made predictive saccades in advance of ball bounce in half of all trials, with saccades directed several degrees above the bounce rather than towards or beyond it. Instead of gaze after the saccade lying-in-wait for the ball to catch-up, gaze instead moved throughout the bounce period. Ongoing head movements ensured that gaze continued to follow the ball laterally during bounce, while vertical eye movements realigned gaze with the ball often within the first 100ms after bounce, which, given the visual-motor delay, suggests that corrective eye movements were planned in advance of the bounce. Participants do not appear to use predictive eye movements to ensure gaze ‘lies-in-wait’ for the ball at or beyond bounce, but rather seem to use predictions to guide ongoing eye and head movements throughout the moment of bounce.