Andrew Prestwich

Are interventions theory-based? Development of a Theory Coding Scheme.

OBJECTIVE Interventions are increasingly described as theory-based; however, the basis for this is often not clear. Advancing behavioral science requires a good understanding of how interventions are informed by, and test, theory. This study aims to develop a reliable method for assessing the extent to which behavioral interventions are theory-based. DESIGN The reliability, usability, and comprehensiveness of an initial coding scheme were improved in 13 iterative stages on the basis of its application to 29 papers, from a systematic review of interventions to promote physical activity and healthy eating. RESULTS The final Theory Coding Scheme contained 19 items, each with satisfactory interrater reliabilities, coding whether a theory or model was mentioned, how theories were used in intervention design, how intervention evaluations tested theory, and the implications of the results for future theory development. CONCLUSION The Theory Coding Scheme is an important methodological innovation, providing a research tool to reliably describe the theoretical base of interventions, inform evidence syntheses within literature reviews and meta-analyses, and stimulate the use of empirical data for theory development.

Does theory influence the effectiveness of health behavior interventions? Meta-analysis.

OBJECTIVE To systematically investigate the extent and type of theory use in physical activity and dietary interventions, as well as associations between extent and type of theory use with intervention effectiveness. METHODS An in-depth analysis of studies included in two systematic reviews of physical activity and healthy eating interventions (k = 190). Extent and type of theory use was assessed using the Theory Coding Scheme (TCS) and intervention effectiveness was calculated using Hedgess g. Metaregressions assessed the relationships between these measures. RESULTS Fifty-six percent of interventions reported a theory base. Of these, 90% did not report links between all of their behavior change techniques (BCTs) with specific theoretical constructs and 91% did not report links between all the specified constructs with BCTs. The associations between a composite score or specific items on the TCS and intervention effectiveness were inconsistent. Interventions based on Social Cognitive Theory or the Transtheoretical Model were similarly effective and no more effective than interventions not reporting a theory base. CONCLUSIONS The coding of theory in these studies suggested that theory was not often used extensively in the development of interventions. Moreover, the relationships between type of theory used and the extent of theory use with effectiveness were generally weak. The findings suggest that attempts to apply the two theories commonly used in this review more extensively are unlikely to increase intervention effectiveness.

The use of implementation intentions and the decision balance sheet in promoting exercise behaviour

Although increasing exercise and fitness has often been associated with positive health outcomes, infrequent exercise participation has remained a problem. Since two distinct motivational and volitional phases to goal pursuit have been proposed, a combined motivational (decision balance sheet, DBS) and volitional (implementation intentions) intervention was predicted to be more effective in increasing exercise behaviour than a control or either strategy alone. A total of 86 students were randomly assigned to one of the four conditions, and were all asked to try to exercise two more times a week than they currently did, over a four week period. Their fitness levels were measured through fitness tests conducted pre- and post-intervention. A priori orthogonal contrasts indicated that the experimental strategies produced a greater increase in exercise frequency and total time spent exercising per week and accordingly showed greater fitness improvements than the control group. Moreover, the volitional groups taken together produced greater increase in time spent exercising and a marginally greater improvement in frequency than the DBS alone. The combined intervention led to improvements in fitness and marginal increases in frequency over the implementation intention alone group. It is proposed that for the combined group the DBS may have aided recall of the implementation intention or increased commitment to it, as remembering and then acting on the plan, in the stated place and time, mediated the implementation intention–behaviour relationship. The combined intervention produced the greatest fitness improvements, indicating that this strategy can lead to important health benefits.

Can Implementation Intentions and Text Messages Promote Brisk Walking? A Randomized Trial

OBJECTIVE To test the efficacy in promoting brisk walking of two theory-based interventions that incorporate implementation intentions and text message (Short Message Service; SMS) reminders directed at ones walking-related plans or goals. DESIGN Participants (N = 149) were randomized to one of three conditions (implementation intention + SMS plan reminder, implementation intention + SMS goal reminder, control) before completing measures at baseline and follow-up 4 weeks later. At follow-up, the experimental groups were given a surprise recall task concerning their plans. All participants completed an equivalent goal recall task. MAIN OUTCOME MEASURES Validated self-report measures of physical activity and measures of implementation intention and goal recall, weight, and waist-to-hip ratio. RESULTS Both intervention groups increased their brisk walking relative to the control group, without reducing other physical activity. The goal reminder group lost the most weight. The SMS plan reminder group recalled more of their plans than the SMS goal reminder group, but the latter were more successful in goal recall. CONCLUSION Both interventions can promote brisk walking in sedentary populations. Text messages aid the recall of, and could enhance interventions that target, implementation intentions and goals.

Using Aversive Images to Enhance Healthy Food Choices and Implicit Attitudes: An Experimental Test of Evaluative Conditioning

OBJECTIVE To examine the effect of communicating images of energy-dense snack foods paired with aversive images of the potential health consequences of unhealthy eating, on implicit and explicit attitudes and food choice behavior. DESIGN Participants were randomly allocated to either an evaluative conditioning (EC) procedure that paired images of snack foods with images of potential adverse health consequences or a control condition that featured images of snack foods alone. MAIN OUTCOME MEASURES Implicit attitudes were assessed pre- and post-intervention. Explicit attitudes and food choice behavior were assessed post-intervention. RESULTS The conditioning intervention made implicit attitudes toward energy-dense snacks more negative, with this effect greatest in those with relatively more favorable implicit attitudes toward these snacks at baseline. Participants in the conditioning intervention were more likely to choose fruit rather than snacks in a behavioral choice task, a relationship mediated by changes in implicit attitudes. CONCLUSION Presenting aversive images of potential health consequences with those of specific foodstuffs can change implicit attitudes, which impacts on subsequent food choice behavior.

Relations Between Implicit and Explicit Measures of Attitudes and Measures of Behavior: Evidence of Moderation by Individual Difference Variables

The moderating role of individual difference variables (Self-Reported Habit Index [SRHI], Need for Cognition [NFC]) on relationships between implicit (Implicit Association Test [IAT], Extrinsic Affective Simon Test [EAST]) or explicit measures of attitude and behavior is assessed in two studies. A dissociation pattern is found on self-report diary measures of behavior. In Study 1, the EAST—behavior relationship is moderated by SRHI; explicit measures of the attitude—behavior relationship are moderated by NFC. In Study 2, the IAT—behavior relationship is moderated by SRHI; explicit measures of the attitude—behavior relationship are moderated by NFC. Higher levels of SRHI and NFC are associated with stronger relationships between the implicit or explicit measures of attitude and the measure of behavior. In Study 2, the SRHI × IAT interaction is replicated for an objective behavior measure. Implications for understanding the relationship between implicit and explicit measures of attitudes and measures of behavior are discussed.

Does monitoring goal progress promote goal attainment? A meta-analysis of the experimental evidence.

Control theory and other frameworks for understanding self-regulation suggest that monitoring goal progress is a crucial process that intervenes between setting and attaining a goal, and helps to ensure that goals are translated into action. However, the impact of progress monitoring interventions on rates of behavioral performance and goal attainment has yet to be quantified. A systematic literature search identified 138 studies (N = 19,951) that randomly allocated participants to an intervention designed to promote monitoring of goal progress versus a control condition. All studies reported the effects of the treatment on (a) the frequency of progress monitoring and (b) subsequent goal attainment. A random effects model revealed that, on average, interventions were successful at increasing the frequency of monitoring goal progress (d+ = 1.98, 95% CI [1.71, 2.24]) and promoted goal attainment (d+ = 0.40, 95% CI [0.32, 0.48]). Furthermore, changes in the frequency of progress monitoring mediated the effect of the interventions on goal attainment. Moderation tests revealed that progress monitoring had larger effects on goal attainment when the outcomes were reported or made public, and when the information was physically recorded. Taken together, the findings suggest that monitoring goal progress is an effective self-regulation strategy, and that interventions that increase the frequency of progress monitoring are likely to promote behavior change.

Can the effects of implementation intentions on exercise be enhanced using text messages

Implementation intentions planning in advance the situation in which one will act, have been proposed to be an effective self-regulatory technique for changing health behaviour. Encouraging people to receive text message reminders of their implementation intentions should enhance their strength and, thus, it was predicted that this combined approach would be particularly effective in increasing exercise. Participants (N = 155) were randomly allocated to one of five conditions (implementation intentions and SMS, implementation intention, SMS or one of two control groups) then completed self-report measures of exercise behaviour and motivation. Four weeks later, they responded to similar items. Results suggested that the combined intervention increased exercise frequency significantly more than the other strategies including the implementation intention group. It is proposed, therefore, that implementation intention effects can be enhanced via plan reminders.

The IAT as a predictor of food choice: The case of fruits versus snacks

One of the issues concerning the application of implicit measures like the IAT is whether they can be successfully applied to consumer choices. The empirical evidence of the predictive validity of the IAT so far has been mixed, both at the level of eating habits and of specific behavioural food choices. Moreover, whereas the predictive validity of the IAT has been tested in a number of studies, its incremental validity has not been studied as thoroughly. In this contribution, four studies, run at different points in time and analysed as a single sample (N = 399), tested the predictive and incremental validity of an IAT of attitudes towards fruits versus snacks on the choice of a fruit or a snack at the end of the experimental session. Specifically, an additive pattern in which both implicit and explicit measures predict independently, and an interactive one in which implicit and explicit measures predict interactively, were tested for the prediction of the behavioural preference towards snacks or fruits. The results showed that the IAT has both predictive and incremental validity, over and above the significant prediction provided by explicit measures for behavioural food choice. Furthermore, no interaction effect between implicit and explicit measures in the behavioural prediction was obtained, supporting the additive rather than the interactive pattern. Finally, only the explicit attitude towards snacks predicted behavioural choice whereas the explicit attitude towards fruits did not. This result indirectly suggests that a single target IAT might be fruitfully adopted in future research.

Individual and collaborative implementation intentions and the promotion of breast self-examination

Implementation intentions, plans relating to when and where behaviours will be performed, have been effective in increasing health behaviour. Two studies are reported that test the impact of this strategy in promoting breast self-examination (BSE), a behaviour shown to aid the early detection of tumours. In study 1, 457 participants were randomly allocated to either implementation intention or control conditions. Implementation intentions significantly increased the likelihood of BSE at one month. The effect of the intervention was marginally significant at six months. Study 2 (N = 101) tested the efficacy of a collaborative implementation intention intervention that required female participants to plan, with a partner, collaborative BSE performance. Results indicated that both implementation intentions and partner involvement were associated with BSE performance at one month, whilst the collaborative implementation intention intervention showed a 100% success rate. Collaborative implementation intentions may reduce forgetfulness. Interventions that encourage partner involvement in planning and enacting behaviour appear to enhance implementation intention utility.