The concept of effortful control in self-regulation or, in everyday language,“willpower,” has survived a century of historical vicissitudes within psychology. Beginning with William James (1890) who made it central for the field's agenda, to its banishment as unscientific at the height of behaviorism, to its resurgence within contemporary psychology in an explosion of work on “self-regulation,” the concept's popularity has waxed and waned. Currently, this now vigorously pursued and intensively researched–but still elusive-construct is more center stage than ever. It is difficult to find a conference in social, personality, or developmental psychology in which self-regulation and self-control—and a host of related executive and agentic functions (eg, planning, future-orientation, goal-directed behavior, effortful control, proactive behavior)—are not major agenda items. As such, it remains a challenge for psychological research …