Saccades are very fast voluntary eye movements, characterized by a consistent relationship of peak velocity, duration, and amplitude, the so-called main sequence (Bahill, Clark, & Stark,
1975; Harris & Wolpert,
2006). Despite being fast, they are also quite accurate (Kapoula & Robinson,
1986; Kowler & Blaser,
1995; van Beers,
2007), even in response to moving targets (Heywood & Churcher,
1981; Ron, Vieville, & Droulez,
1989; Keller & Steen Johnsen,
1990; de Brouwer, Missal, & Lefèvre, 2001; de Brouwer, Missal, Barnes, & Lefèvre,
2002; de Brouwer, Yuksel, Blohm, Missal, & Lefèvre,
2002; Eggert, Guan, Bayer, & Büttner,
2005; Guan, Eggert, Bayer, & Büttner,
2005; Etchells, Benton, Ludwig, & Gilchrist,
2010). Depending on many factors such as stimulus characteristics and fixation-target timing conditions, training, and age, it takes about 100–300 ms to initiate a target-directed saccade. Typical mean saccadic latencies are about 180–200 ms in man (Saslow,
1967; Fischer & Ramsperger,
1984; Gellman & Carl,
1991; Munoz, Broughton, Goldring, & Armstrong,
1998). Saccades reflect a more final choice of the oculomotor system, because shortly before their onset about 80–100 ms (“dead time”) their amplitude cannot be altered (Wheeless, Boynton, & Cohen,
1966; Becker & Jürgens,
1979; Aslin & Shea,
1987; Ludwig, Mildinhall, & Gilchrist,
2007).