Towards a Unitary Approach to Human Action Control

From its academic beginnings the theory of human action control has distinguished between endogenously driven, intentional action and exogenously driven, habitual, or automatic action. We challenge this dual-route model and argue that attempts to provide clear-cut and straightforward criteria to distinguish between intentional and automatic action have systematically failed. Specifically, we show that there is no evidence for intention-independent action, and that attempts to use the criterion of reward sensitivity and rationality to differentiate between intentional and automatic action are conceptually unsound. As a more parsimonious, and more feasible, alternative we suggest a unitary approach to action control, according to which actions are (i) represented by codes of their perceptual effects, (ii) selected by matching intention-sensitive selection criteria, and (ii) moderated by metacontrol states. Human action control and decision-making are traditionally understood as emerging from the competition between will (representing intentionality and rationality) and habit (representing automatized and stimulus-driven tendencies). This dual-route concept is still dominant in behavioral, clinical, and neuroscientific research. Criticism has been accommodated by allowing some degree of continuity between the two routes, but without specifying clear-cut criteria to locate behavior on this continuum, however. We suggest replacing the dual-route model by a unitary model of action control which assumes that goal-directed actions are represented in terms of expected action effects that are selected according to a match between intended and expected action effects.