Abstract
Prediction is a central skill in human life. As our environment is constantly changing, both as a consequence of our actions and independently of us, it's necessary to anticipate when and where future events will happen, in order to be able to synchronize our actions with them and to proficiently interact with the world (e.g. Gredebäck et al. 2002). The study of interception abilities represents a good option to investigate this topic, as interception is a quite common task and, at the same time, it strongly requires anticipation skills. In fact it wouldn't be possible to catch any target acting in a purely reactive manner, due to the visuo-motor transmission delays of the human body (Zago & Lacquaniti, 2005). In our experiments we measured how different parameters of two-dimensional target motion (i.e. curvature, speed and acceleration) affected the predictive strategy adopted by subjects. Two predictive tasks were compared: one involving the only visual estimation of the arrival point of a virtual target and the other requiring subjects to directly intercept the virtual target by pointing on it with their index finger (vision plus motor involvement). This way it has been possible to understand whether the goal of a predictive effort affects how prediction is performed. The study of the recorded index finger motion allowed us also to study the kinematic features of predictive actions. Particular attention was devoted to understand if an internal model of target motion is built and exploited in prediction. Moreover a further investigation was performed to evaluate whether habituation to a gravitational environment (i.e. where objects move according to the gravitational laws) plays a role in determining predictive performances.