Abstract
Many studies in interceptive timing only consider visual information provided by the moving target in order to explain how action is executed and, largely ignore the contribution of the temporal and spatio-temporal reliability of the feedback. We address how these two aspects of the feedback affect action kinematics in intercepting virtual parabolic balls with the hand. In some sessions the feedback on successful timing was temporally reliable (a beep), but less robust in terms of the grip aperture at the time of the beep. In other sessions we gave spatio-temporal reliable feedback by providing haptic information through a tennis ball stuck on the data glove in addition to the beep. Within each session, we showed parabolic paths with four flight durations (0.606, 0.776, 0.945, 1.115 s) in two different viewing conditions (early and full vision). We expect to observe differences between type of feedback when subjects could not rely on online vision (early vision) to time their catch and rather had to plan the movement by anticipating the expected feedback. In full vision subjects started close the hand earlier when haptic feedback was provided but there were no differences between type of feedback in the velocity of the closing hand which was clearly bell-shaped denoting great capacity to anticipate the moment of the contact. However, when subjects only saw the initial 40% of the path, velocity profiles in the temporally-reliable condition were no longer bell-shaped, specially for paths with longer duration (i.e. longer blank period) which reflects less capacity to anticipate the contact. Interestingly, when haptic information was present grip velocity profiles were again bell-shaped as if subjects anticipated better the moment of contact. The spatio-temporal feedback seems to compensate a bit for the absence of late vision when planning interceptive movements.
Meeting abstract presented at VSS 2015