The strength of habit

Despite its presence in the psychological literature for more than one hundred years, the habit concept, the means by which habit serves to control human behaviour in daily life and the means by which psychologists might promote or change strong habits remain active research topics. Although habit and past behaviour have been acknowledged determinants of human social behaviour in various theoretical models (e.g., Bagozzi & Warshaw, 1990; Ouellette & Wood, 1998; Triandis, 1977), research that might have explored the relative roles of motivational (reflective) and habitual (automatic) processes in human action was hindered by the lack of an adequate measure of habit (Eagly & Chaiken, 1993). Gardner’s (2015) engaging discussion of the literature is a welcome reminder of how research in this field has progressed. Psychologists are now somewhat closer to realising empirical evidence to justify James’ (1891) recommendation to the young to make habitual, as many useful actions as possible. Habitual behaviours proceed without effortful cognitive mediation and are performed even under conditions of egodepletion, when self-control and motivational energy are directed elsewhere (Hagger, Wood, Stiff, & Chatzisarantis, 2010; Neal, Wood, & Drolet, 2013). Different accounts of habit converge upon three elements: a habit has a history of repetition (e.g., Aarts, Verplanken, & van Knippenberg, 1998; Lally, van Jaarsfeld, Potts, & Wardle, 2010; Mullan, Allom, Fayn, & Johnston, 2014; Verplanken & Aarts, 1999), a high degree of automaticity (e.g., Aarts & Dijksterhuis, 2000; Orbell & Verplanken, 2010; Verplanken & Orbell, 2003) and is cued in stable contexts (e.g., Neal, Wood, Labrecque, & Lally, 2012; Orbell & Verplanken, 2010; Wood & Neal, 2007). Our contention, however, is that habit should not be equated with the concept of an impulse (Gardner, 2015) or with the trait characteristic of impulsivity (e.g., Patton, Stanford, & Barratt, 1995; Stanford, Mathias, Dougherty, Lake, Anderson, & Patton, 2009, see also Strack & Deutsch, 2004 for an alternative use of the term), which amongst other things may be equated with capriciousness (the antonym of a habitual response). It is true that a habitual response may take many forms: it may be an overt act, or a sequence of acts, a mental response (e.g., Verplanken, Friborg, Wang, Trafimow, & Woolf, 2007) or even an emotional reaction (e.g., Verplanken & Fisher, 2014; Verplanken & Roy, 2013), but a habit does not necessitate an affective component. To define habit as an impulse also risks confusion with related concepts such as temptation and addiction (Reddish, Jensen, &