The Influence of Foreperiod Duration on the Preparation and Control of Sequential Aiming Movements

Reaction and movement times to the first target are typically longer for
two-target sequential movements compared to one-target movements (i.e., one-target advantage). While foreperiod duration has been varied
randomly in past studies, there has been no systematic investigation of how
this interval influences the planning and execution of sequential movements. According to the Movement Integration Hypothesis, segments are
loaded into a buffer prior to response initiation, which then enables the
second segment to be implemented during movement to the first target. The
Movement Constraint Hypothesis is based on the assumption that variability in limb trajectories to the first target are constrained in order to meet
the accuracy demands at the second target. To test if the one-target
advantage is influenced by foreperiod duration, we performed two experiments. In Experiment 1, participants performed one- and two-target
movements in two separate blocks of trials. In Experiment 2, target
conditions were randomized from trial to trial. The interval between
target(s) appearing and stimulus tone (i.e., foreperiod) was varied randomly (0, 500, 1000, 1500, 2000 ms). The results of Experiment 1 revealed
that while the one-target advantage in reaction time was not influenced by
foreperiod duration, the one-target advantage in movement time increased
as foreperiod duration increased. There were also greater decreases in
variability from peak velocity to the first target in the two- compared to
one-target condition. In Experiment 2, the one-target advantage in both
reaction and movement time increased as the length of the foreperiod
increased. However, there was no difference in limb trajectory variability
between target conditions. Collectively, these results support the movement integration hypothesis by demonstrating that planning and execution
of sequential aiming movements is influenced by the interval prior to the
stimulus. Support for the Movement Constraint Hypothesis was revealed
only when the number of targets was the same from trial to trial.