Abstract
Habitual behaviours are elicited when a familiar context activates cue-behaviour associations that have been learned through previous performance. A core hypothesis within habit theory is that, by virtue of its automaticity, habit weakens the impact of intention on action, such that in facilitating conditions, action will be guided more by habit than momentary intentions. This has led to recommendations that habit formation be harnessed as a mechanism for sustaining desirable behaviour over time, when people would otherwise relapse due to loss of motivation. This article reviews theory and evidence around the hypothesized interaction between habit and intention as determinants of behaviour. We first qualify the hypothesis by clarifying that it pertains only to determinants of the instigation of action, rather than execution. Next, drawing on a systematic review of 52 behaviour-prediction studies, we highlight mixed empirical support for the interaction. We argue that ostensibly inconsistent findings can be reconciled by recognizing the distinction between the direction and strength of intention, and identifying the "facilitating conditions" that may determine the relative influence of habit and intention on behaviour. Evidence demonstrates that when self-control is diminished, people act habitually regardless of intention direction or strength. When people possess self-control, habits can help people to act on favourable but weakened intentions, but intentions that oppose habitual tendencies can override habitual influence. This has important implications for behaviour change: even if habit has formed, a minimal level of favourable conscious motivation may be required to sustain behaviours over time. Social psychology might fruitfully move beyond askingwhetherhabit moderates the intention-behaviour relationship, and instead probehowandin which conditionshabits and intentions interact.