We quantify the nature and frequency of anticipation behaviours in professional tennis using video coding of incidents where the time delay between the opponent's stroke and the reaction of the player were recorded. We argue that anticipation is based on uncertain information and should lead in some situations to erroneous decisions. We identified the transition between reaction (with 100% accuracy in the selection of where the ball is played on the court) and anticipation (with less than 100% accuracy) as being 140-160 ms after ball contact. Anticipation behaviours occurred on between 6.14% and 13.42% of the coded situations. These anticipation behaviours appeared almost exclusively in 'unfavourable' situations, where the opponent had a significant tactical advantage, with the type of playing surface having only a limited effect. Moreover, the decrease in accuracy with shorter response times is not monotonic, with an increase in response accuracy being observed for times shorter than 120 ms before ball contact. We propose that very early anticipation behaviours occur when players use significant context-specific information before the opponent's stroke. When such information is not available, players produce anticipation behaviours that are closer to the moment of ball-racket contact using information that is more likely to be based on the opponent's preparation of the stroke. This study opens new directions for research focusing on the testing and training of anticipation in fast ball sports.

In many situations, it is necessary to predict when a moving object will reach a given target even though the object may be partially or entirely occluded. Typically, one would track the moving object with eye movements, but it remains unclear whether ocular pursuit facilitates accurate estimation of time-to-contact (TTC). The present study examined this issue using a prediction-motion (PM) task in which independent groups estimated TTC in a condition that required fixation on the arrival location as an object approached, or a condition in which participants were instructed to pursue the moving object. The design included 15 TTC ranging from 0.4 to 1.5 s and three object velocities (2.5, 5, 10 deg/s). Both constant error and variable error in TTC estimation increased as a function of actual TTC. However, for the fixation group only, there was a significant effect of object velocity with a relative overestimation of TTC for the slower velocity and underestimation for the faster velocity. Further analysis indicated that the velocity effect exhibited by the fixation group was consistent with participants exhibiting a relatively constant misperception for each level of object velocity. Overall, these findings show that there is an advantage in the PM task to track the moving object with the eyes. We explain the different pattern of TTC estimation error exhibited when fixating and during pursuit with reference to differences in the available retinal and/or extra-retinal input.

Infants with MMC responded to the treadmill by stepping (but less so than infants with TD) and showing increased motor activity, but they demonstrated a different developmental trajectory. Future studies are needed to explore the impact of enhancing sensory input during treadmill practice to optimize responses in infants with MMC.

No abstract