Different spatio-temporal strategies for controlling a striking gesture to slide an object toward a target distance

Abstract Humans never perform the same movement twice, and there is interindividual variability in the spatio-temporal regulation of movements. The literature on striking gestures suggests that three types of spatio-temporal control can be observed when coping with task difficulty: increasing the amplitude of the movement while keeping its duration constant; keeping the amplitude of the movement constant and reducing the duration of the movement; or increasing both amplitude and duration of the movement by varying on the acceleration at impact. In this study, participants (n = 33) striked a cube which slides inside a gutter toward a target distance. Task difficulty varied as a result of the combination of three factors: surface material at the base of the gutter (aluminum and balsa), target distance (25 cm and 50 cm) and surface slope (-10°, 0°, + 10°). Clustering (K-Means) and correlational analyses on the hand movement data as a function of task difficulty confirmed that participants used the above-mentioned three strategies for the spatio-temporal control of the ballistic strike gesture. Although each cluster differed in how they exploited strike amplitude and duration to control movement, impact speed functioned as an invariant control variable across clusters, which did not differ in mean performance (spatial error).