In order to perform an interceptive task such as catching a ball, an actor can either predict where and when the ball can be intercepted, as has been suggested by many authors (McLeod, McLaughlin, & Nimmo-Smith, 1985; Montagne & Laurent, 1994; Rosengren, Pick, & Von Hofsten, 1988), or can continuously tune the movement to information specifying the required lateral hand velocity (Peper, Bootsma, Mestre, & Bakker, 1994). Whatever information is used, it seems inevitable that (the rate of change of) the angles ϕ and θ (see Figure 1) are involved