3.1.1 Event vs emergent timing of repetitive movements
Recently, Zelaznik and colleagues (Ivry, Spencer, Zelaznik, & Diedrichsen, 2002; Spencer, Zelaznik, Diedrichsen, & Ivry, 2003; Zelaznik, Spencer, & Ivry, 2002) proposed that two qualitatively different control processes could be used for the timing of repetitive movements. When the periodic movements are marked by salient events, such as during finger tapping, control processes include a temporal representation of the target interval between those events. That form of control is referred to as event timing (Ivry et al.). On the other hand, when the movements are smooth and continuous, such as during continuous circle drawing, the ability to maintain a consistent rate does not require an explicit representation of the interval duration. Rather, Zelaznik and colleagues hypothesized that timing under such conditions emerges from the dynamics of trajectory control. Borrowing from the classic article of Turvey (1977), they refer to that form of control as emergent timing (Spencer et al.).