Amongst the plethora of behaviour change models an uneven frequency of theory use exists; with early social cognition models generally dominating the literature \citep*{Davis_2014}. These include the Health Belief Model (HBM) and the Theory of Planned Behaviour (TPB). Collectively, these models take a continuum approach to behaviour change, examining the predictors and precursors of health behaviours and comprise of similar, overlapping constructs (Michie et al., 2005).  The Health Belief Model \citep*{Rosenstock_1974}  (Glanz, Rimer & Viswanath, 2008) in its revised entirety (Rosenstock et al., 1988) is based upon value-expectancy concepts. It suggests that one's willingness to change depends upon one's perceived susceptibility to ill-health and consequences of disease, the perceived benefits and barriers to change, levels of self-efficacy to succeed in change, and instrinsic or extrinsic cues to action. It has been successfully applied in instances of ... However, the evidence supporting the application of the HBM is generally weak and its predictive capacity is limited (Taylor et al., 2006). Possibly the most useful element presented within this model concerns the value of ‘perceived threat’ of a behaviour as a key indicator of behavioural change. This concept re-emerges within alternative theories, including Protection Motivation Theory \citep*{Maddux_1983}. This theory incorporates the value of emotion into health behaviours and proposes that protective health behaviours are the product of threat appraisal and one's ability to cope with said threat. Specifically, threat appraisal incorporates the the severity, susceptibility and emotional response (namely, fear) to a health behaviour, whilst one's coping appraisal is influenced by perceptions of self-efficacy and response effectiveness (i.e. that enacting a given behaviour will reduce the likelihood of threat) (Rogers, 1975).  Environmental sources of information, in addition to personal experience, subject the individual to adopt either an adaptive or maladaptive coping response. Methods to increase a ‘perceived threat’ of a behaviour have proven somewhat useful in shaping health behaviours; as evidenced by pictorial warnings on cigarette packaging eliciting increased intentions to quit smoking significantly more so than text-only warnings (Noar et al., 2016). However, a prevailing concern that both the HBM and PMT models share surrounds their failure to account for the impact of social, economic and environmental factors on health behaviours; in addition to their disregard of habitual behaviours.
The Theory of Planned Behaviour, like its predecessor the Theory of Reasoned Action (Fishbein & Ajzen, 1975), emphasise a central role for social cognition in the form of subjective norms. It proposes that behaviour implementation intentions are a function of individual attitudes concerning the desirability of a behaviour, in addition to the subjective norms of that behaviour; and the perceived approval gained from adhering to such norms. The TPB extends upon the Theory of Reasoned Action by incorporating the construct of perceived behavioural control (PBC) as an additional predictor of intention and behaviour. This construct of volitional control is considered conceptually similar to self-efficacy but reflects the perceived ease of performing a behaviour and the extent to which it can become habitual over time. The TPB thus incorporates social and environmental factors, in addition to the role of past behaviour. It confers greater predictive performance of behaviours than that of the HBM, accounting for between 20-30% of the variance in adult health behaviours in the US and UK (Taylor et al., 2006). However, this predictive value is relatively low; thus interventions based upon such models may lack potential for positive change. 
The Trans-Theoretical Model (Prochaska et al., 1992; Prochaska & Velicer, 1997) or 'Stages of Change' model comprises possibly one of the most prevailing models represented within the behaviour change literature \citep{Davis_2014}. This framework proposes that the behaviour change process comprises six dynamic and distinguishable non-linear stages; including pre-contemplation (not intending to change), contemplation (thinking about change), preparation (intending to change a behaviour and initiating change with small steps, action (changing the behaviour), maintenance (sustaining the new behaviour), and termination (when there is no temptation to revert to the original undesirable behaviour). Individuals can relapse at any one of these stages. This model has been used to explain several health behaviours, including smoking, exercise, alcohol use, and screening behaviours (Marshall & Biddle, 2001; Rosen, 2000). It also holds the capacity to serve as a foundation for tailoring interventions to participants based on their stage of change, applicable at both an individual and a community level (Taylor et al., 2006).
- The TTM has been criticised on several grounds (West, 2005) and its empirical support has been questioned by systematic review findings (e.g., Cahill, Lancaster, & Green, 2010; Etter & Perneger, 1999; Littell & Girvin, 2002; Whitelaw, Baldwin, Bunton, & Flynn, 2000).