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Previous developmental research examining sensorimotor control of the arm in school-age children has demonstrated age-related improvements in movement kinematics. However, the mechanisms that underlie these age-related improvements are still unclear. This study hypothesized that changes in sensorimotor performance across childhood can be attributed, in part, to the development of state estimation, defined as estimates computed by the central nervous system, which specify both current and future hand positions and velocities (i.e., hand “state”). Two behavioral experiments were conducted, in which 6- to 12-year-old children and young adults executed goal-directed arm movements. Results from Experiment 1 revealed that young children (i.e., ∼6–8 years) have less precise proprioceptive feedback for static (i.e., stationary) hand state estimation compared with older children (i.e., ∼10–12 years), resulting in increased variability of target-directed reaching movements. Experiment 2 demonstrated that young children rely on delayed and unreliable state estimates during the execution of goal-directed hand movements (i.e., dynamic state estimation), resulting in both increased movement errors and directional variability. Collectively, these results suggest that improvements in sensorimotor behavior across childhood can be attributed, at least partially, to the development of both static and dynamic state estimation.

The extant developmental literature investigating age-related differences in the execution of aiming movements has predominantly focused on visuomotor coordination, despite the fact that additional sensory modalities, such as audition and somatosensation, may contribute to motor planning, execution, and learning. The current study investigated the execution of aiming movements toward both visual and acoustic stimuli. In addition, we examined the interaction between visuomotor and auditory-motor coordination as 5- to 10-yr-old participants executed aiming movements to visual and acoustic stimuli before and after exposure to a visuomotor rotation. Children in all age groups demonstrated significant improvement in performance under the visuomotor perturbation, as indicated by decreased initial directional and root mean squared errors. Moreover, children in all age groups demonstrated significant visual aftereffects during the postexposure phase, suggesting a successful update of their spatial-to-motor transformations. Interestingly, these updated spatial-to-motor transformations also influenced auditory-motor performance, as indicated by distorted movement trajectories during the auditory postexposure phase. The distorted trajectories were present during auditory postexposure even though the auditory-motor relationship was not manipulated. Results suggest that by the age of 5 yr, children have developed a multisensory spatial-to-motor transformation for the execution of aiming movements toward both visual and acoustic targets.