 This is a prospective interventional study involving young children who will all receive non-invasive, passive assessments of sensory and motor function. In addition a subpopulation of young children with cerebral palsy will participate in a randomized controlled trial of constraint-induced movement therapy, a routinely prescribed therapy used in clinical practice for children with motor difficulties. The study attempts to apply a rigorous scientific approach to study a widely used but poorly studied practice. The design is an RCT with wait-list controls to allow all children to benefit from the therapy, even if they are randomized to the control group. All children, regardless of group allocation will continue with their standard of care occupational and physical therapy throughout the study. 