Quiet eye and eye quietness: Electrooculographic methods to study ocular activity during motor skills

Abstract

Camera-based eye tracking research has revealed that experts make longer fixations on the target of an action (e.g., the ball in golf putting) prior to and following movement onset, compared to novices. Yet it is not clear how ocular activity affects motor performance. It is possible that the limited temporal resolution of camera systems has held back progress on this issue. We analysed horizontal EOG (512 Hz, 0.1-30 Hz filtered) from ten expert and ten novice golfers as they putted 60 balls to a 2.4 m distant hole. We used multiple voltage thresholds to measure the duration of the final fixation (quiet eye; QE) with its pre- and post-movement onset components. We also measured ocular activity across time as the standard deviation of the EOG in 0.5 s bins, –4 to +2 s from movement onset (eye quietness; EQ): lower values correspond with greater quietness. Finally, we measured ball address and club swing durations using infrared and sound sensors. Total QE duration did not differ between groups. However, experts had shorter pre-movement QE and longer post-movement QE than novices. Experts had less EQ before movement onset and greater EQ after movement onset. EQ was inversely correlated with QE duration, concurrently validating EQ as an index of ocular activity. Experts had longer swing durations than novices. Swing duration correlated positively with post-movement QE and negatively with post-movement EQ. Our findings provide new evidence that expert-novice differences in ocular activity may reflect differences in the kinematics of how experts and novices execute motor skills.