The effect of conscious control on movement automaticity

Abstract

This thesis presents four experiments aimed at testing whether conscious control decreases movement automaticity. Although the term “movement automaticity” is often used in the motor control literature, it is seldom measured in experiments that examine the role of conscious control in movement. A possible reason for this lack of operationalization is that the experiments are based on dualistic assumptions. These assumptions prescribe that conscious control and movement automaticity can be operationalized based on the same phenomena. That is, any increase in conscious control is taken to simultaneously indicate a decrease in movement automaticity. Although this may make intuitive sense, it entails that the hypothesis that conscious control decreases movement automaticity is accepted before it is tested. To test the hypothesis more objectively, a separate measure of movement automaticity is needed. To derive such an independent operationalization of movement automaticity, this thesis draws on existential phenomenology, rather than dualism. This change in perspective makes it possible to define movement automaticity as background corrections. When movements are ongoing, these background corrections occur beyond the grasp of conscious control and therefore represent movement automaticity. The subsequent 4 experiments present progressive steps toward testing the hypothesis that conscious control decreases movement automaticity. The first experiment investigates whether different methods of studying conscious control should be combined or used separately. The second, third and fourth experiment investigate the association between conscious control and three measures related to movement automaticity: movement variability, between-trial functional variability and within-trial functional variability, respectively. Results of these experiments provide partial support for the notions that movement automaticity may be operationalized as within-trial functional variability and that conscious control may decrease movement automaticity.