ABSTRACT
Executive functions (EF) are a complex set of supervisory functions that are involved in the control of mental processes. Burgess and Simons (2005) describe EF as those capacities that make people effective in the real world, allowing them to adapt to new situations and to develop and pursue their life goals in a constructive way. Lezak (1982) distinguished higher order EF from hierarchically lower cognitive functions based on the problems with which they are associated. Cognitive functions concern the knowledge, skills and intellectual equipment people may possess, addressing what they know or are able to do, whereas EF are related to whether and how people actually use these abilities. This implies that patients with impaired EF may have preserved cognitive functions, but fail to use them when needed. Hence, impairments in EF will have severe consequences for daily life functioning of patients since they are needed in situations that are novel, complex, offer little structure and cannot be dealt with in a routine manner. Such unstructured task situations are common in daily life and require a new, problem-solving approach, which has to be planned and executed adequately.
