In their article “The Concept of Voluntary Consent,” Robert Nelson and colleagues (2011) argue for two necessary and jointly sufficient conditions for voluntary action: intentionality, and substantial freedom from controlling influences. They propose an instrument to empirically measure voluntariness, the Decision Making Control Instrument. I argue that (1) their conceptual analysis of intentionality and controlling influences needs expansion in light of the growing use of behavioral economics principles to change individual and public health behaviors (growing in part by the designation (...) of “The Science of Behavior Change” as a new National Institutes of Health [NIH] Roadmap Activity); and (2) that their measure of voluntariness that relies on self-perceived intentionality and extent of control is unreliable, given findings from behavioral economics and cognitive science that show that our perceptions about the intentionality and control of our own and others’ decisions and actions are remarkably skewed and un-insightful. (shrink)