Control of rapid aimed hand movements: The one-target advantage

A series of 8 experiments examined the phenomenon that a rapid aimed hand m ovement is executed faster when it is performed as a single, isolated movem ent than when it is followed by a second movement (the 1-target advantage). Three new accounts of this effect are proposed and tested: the eye movemen t hypothesis, the target uncertainty hypothesis, and the movement integrati on hypothesis. Data are reported that corroborate the 3rd hypothesis, but n ot the first 2 hypotheses. According to the movement integration hypothesis , the first movement in a series is slowed because control of the second mo vement may overlap with execution of the first. It is shown that manipulati ons of target size and movement direction mediate this process and determin e the presence and absence of the 1-target advantage. Possible neurophysiol ogical mechanisms and implications for motor control theory are discussed.