Abstract
This chapter shows that executive functions and motor planning are impaired in Williams syndrome (WS). It assesses inhibition (such as inhibition of a prepotent response) and its influence on social functioning, and evaluates how the cascading developmental effects of poor planning ability impact on the wider functioning of other aspects of cognition such as performance on visuospatial tasks. It considers studies that have investigated the interplay between multiple executive functions to resolve the mixed evidence relating to executive dysfunction in WS. Motoric planning is discussed in terms of walking, stairdescent, and reaching studies that reveal evidence for poor motor planning in WS. The chapter highlights how the use of neuroimaging techniques and analysis of movement in real-world situations has advanced the understanding of executive function and motor planning in typical development as well as in groups with neurodevelopmental disorders including WS.