Chapter 2: Literature review
A. MRC framework for developing and evaluating complex interventions
2.8 Behaviour change theories
The ultimate goal of a weight loss intervention is to attain weight loss by producing the desired change in behaviour. Glanz et al. (1990) state that a theoretical understanding of behaviour change is required to develop interventions which are effective and evidence-based. According to Davis et al. (2014), theory refers to knowledge regarding mechanisms of action, moderators of change and the largely accepted assumptions about human behaviour and the factors which influence these assumptions.
58 As already stated, the UK MRC considers the application of theory into intervention development and evaluation as an integral step in intervention development [Skivington et al., 2021; Craig et al., 2008].
This approach allows for causal determinants of behaviour to be identified, which can then be targeted by the intervention using appropriate behaviour change techniques [Michie et al., 2008; Hardeman et al., 2005; Michie & Abraham, 2004]. Application of theory also allows researchers to determine whether an intervention failed because it had no effect on a hypothesised mediator, or whether the hypothesised mediator had no effect on behaviour, thus enabling efficient refinement of the intervention [Rothman, 2009, 2004; Michie & Abraham, 2004].
There are four major theories of behaviour change identified by Glanz et al. (2008), namely: The Social Cognitive Theory (SCT), The Transtheoretical (Stages of Change) Model (TTM), The Health Belief Model (HBM) and The Theory of Planned Behaviour (TPB). Continuum theories like the SCT and HBM, assume that variables such as intention and skills influence behaviour while stage theories, like the TTM, assume that behaviour change occurs in a process over several stages [Wang et al., 2019].
2.8.2 The Social Cognitive Theory (SCT)
Bandura’s SCT developed from the Social Learning Theory in 1986 posits that external factor (personal and environmental) influence behaviour in a triadic interaction [Bandura, 1986]. (Figure 2.4).
Figure 2.4: Bandura’s Social Cognitive Theory model [Bandura, 1986]
This theory uniquely focuses on social influence and social reinforcement. The SCT is therefore useful to explain how behaviour is regulated through control and reinforcement so that the desired behaviour can be maintained over time. It consists of five constructs: reciprocal determinism (refers to the interaction between the person, environment and behaviour); behavioural capability (refers to the actual ability to perform a behaviour through knowledge and skills); observational learning
59 (reproducing actions after observing the behaviour being conducted by others); reinforcements (internal and external responses to a behaviour which affect the likelihood of it being continued);
expectations (a judgement of the likely consequences produced by a behaviour); and self-efficacy (a judgement of one’s ability to perform the behaviour) [Bandura, 1986]. The SCT places emphasis on the individual and the environment, making it’s use widely acceptable for public health interventions.
There are however a few limitations associated with its use in intervention planning. The theory pays minimal attention to emotion or motivation and assumes that environmental changes will automatically lead to behavioural changes. The constructs of the theory are also loosely organised and the extent to which each one impacts behaviour is undefined [LaMorte, 2019].
2.8.3 The Transtheoretical Stages of Change Model (TTM)
The TTM [Prochaska, 1979; Prochaska and DiClemente, 1983; Prochaska et al., 1992] assumes that change occurs during a process of six stages (Figure 2.5).
Figure 2.5: Transtheoretical Stages of Change [Prochaska, 1979]
Precontemplation is the stage in which people are not intending to make a change in the near future (the next 6 months). The contemplation stage is when people intend to change but are not yet taking action to do so (within the next 6 months). Preparation is the stage in which people have a plan of action and intend to make the change within the next month. Action is the stage when the behaviour is performed and maintenance is the stage when work is performed to prevent a relapse. Termination is when total efficacy is attained and the behaviour can be maintained.
The TTM is often applied to interventions targeting addictive behaviour and it assumes that individuals at the same stage have similar barriers and problems and consequently, can be helped with the same type of intervention [Nisbet & Gick, 2008]. This model is more favoured by practitioners than
60 researchers as the constructs are not well defined and the model does not clearly explain how individuals change, or why some change more effectively or quickly than others [Morris et al., 2012].
2.8.4 The Health Belief Model (HBM)
The HBM [Rosenstock et al., 1988; Rosenstock, 1960, 1966, 1974; Hochbaum, 1958] proposes that behaviour is determined by a number of beliefs regarding the threats to an individual’s wellbeing and the effectiveness of the recommended health behaviour (Figure 2.6).
Figure 2.6: The Health Belief Model [Hochbaum, 1958]
Perceived threat is linked to how ready an individual is to take action and is at the core of the model.
It is influenced by beliefs of individuals regarding their perceived susceptibility to a specific threat, as well as the perceived seriousness of the expected consequences associated with it. The extent to which a behaviour is beneficial is determined by weighing up the perceived benefits associated with the behaviour against the perceived costs and negative implications that may result from it (perceived barriers). Some constructions of the HBM include self-efficacy and, internal and external cues to action, which trigger adoption of the behaviour [Sharma & Romas, 2012; Becker, 1974; Rosenstock 1966; Hochbaum, 1958]. Researchers suggest that perceived barriers are the most influential construct of behaviour in the HBM [Janz & Becker, 1984].
There are two well established criticisms of this model which include the following: 1) the constructs of the model and the inter-relationships between them are not well defined; and 2) social, economic or unconscious influences on behaviour are not considered [Jackson, 2005].
61 2.8.5 The Theory of Planned Behaviour (TPB)
The TPB (Figure 2.7) is one of the most commonly applied theories of behaviour and most widely cited [Ajzen, 1985, 1991; Ajzen & Madden, 1986]. It started off as the Theory of Reasoned Action [Fishbein & Azjen, 1975].
Figure 2.7: The Theory of Planned Behaviour [Ajzen, 1985, 1991]
The TPB posits that an individual’s intention is the best predictor of behaviour; the core of this model is thus behavioural intent. According to the model intention is influenced by attitude toward a behaviour (beliefs and values regarding the outcome of a behaviour) and subjective norms (beliefs about what others think one should do and thus includes social pressure). Intention is also an outcome of perceived behavioural control (perceived ease or difficulty related to performing the behaviour).
The TPB therefore suggests that achieving the behavioural outcome depends on motivation (intention) and self-efficacy (behavioural control) [Ajzen, 1985, 1991].
Limitations of the TPB that have been identified include the following: 1) variables such as fear, threat, mood or past experiences which can impact intention and motivation, are not accounted for; 2) environmental or economic factors are also not considered; 3) perceived behavioural control was an important addition to The Theory of Reasoned Action, however, no detail regarding actual control over behaviour is provided; 4) the theory does not address the time frame between “intent” and
“behavioural action”; and 5) the theory assumes that opportunities and resources required to perform the behaviour have been acquired, regardless of intention [LaMorte, 2019].
Researchers in public health tend to prefer the TPB above the HBM, but because of the mentioned limitations, additional components from other behavioural theories are often integrated with the TPB constructs to make the model more comprehensive [LaMorte, 2019; Taylor et al., 2007; Armitage &
Conner, 2001]. Some researchers conclude that the TPB should be used to explain and predict behaviour to identify specific contributing factors of behaviour to be targeted in interventions, rather
62 than designing and planning the type of intervention that will result in behaviour change [Webb et al., 2010; Taylor et al., 2007; Hardeman et al., 2002]. Hardeman et al. (2002:149) supports this with the following statement: “even when authors use the TPB to develop parts of the intervention, they seem to see the theory as more useful in identifying cognitive targets for change than in offering suggestions on how these cognitions might be changed”. The TPB is therefore specifically useful, and preferred by researchers, for intervention development that involves identification of components of a behaviour that need to be targeted to bring about behaviour change.
2.9 Feasibility testing