The overarching goal of public health is to maximise the health of the population, and to achieve this we need evidence about what works and what does not work. Good studies are difficult to design and implement, and interpretation of their results and conclusions is not always as straightforward as we might hope. How, then, can we make the best use of this information? In the next three chapters we look at ways to identify, appraise, integrate and interpret the literature to generate the evidence we need to inform policy and practice. In this chapter we focus on interpreting the results from a single study, because if they are not valid they will be of limited value. The central question we have to answer when we read a study report is, ‘Are the results of the study valid?’

This chapter reflects on how evidence from realist trials and systematic reviews might be of value, not only in drawing conclusions about specific interventions and their theories of change but also in testing and refining the middle range theories which inform these and other interventions. While evaluation evidence should be of most immediate use in informing decisions about the implementation of the specific interventions being evaluated, a broader and more enduring use for evaluation could be in suggesting refinements to middle range theory. Such refinements might then be used to inform and influence the next generation of complex health interventions. In order to be useful in assessing the validity of middle range theory, evaluations will need to assess interventions informed by a limited number of middle range theories comprising a limited number of well-defined constructs. There may be value in conducting proof of principle studies separately from more pragmatic evaluations in order to test and refine middle range theory.

This chapter explores how policymakers and practitioners in settings beyond the sites of evaluation might make use of evidence from realist trials and systematic reviews, plus local needs assessment, to identify the best candidate interventions for their local contexts. To do this, local decision-makers need to assess how likely are interventions to achieve benefits in their contexts. This is partly a matter of assessing whether interventions are likely to be feasible, accessible and acceptable in their settings, which will be influenced by local capacity and norms. It is also a matter of assessing whether intervention mechanisms will be triggered and whether these are likely to generate beneficial outcomes. This will be influenced by what aetiological mechanisms are generating adverse outcomes in the context and hence what vulnerabilities exist which the intervention may be able to address. It will also be influenced by whether the local context provides affordances so that potential beneficiaries may be able to benefit from the intervention. Thinking through these issues should enable local policymakers and practitioners to decide whether such interventions could be delivered immediately at scale, be implementing but only within evaluated pilot studies or be rejected in favour of other interventions.

Progress to date has varied between different sub-disciplines and this final chapter will touch on common themes throughout. Psychology as a discipline has much to gain from the digital age, especially following the mass adoption of smartphohes. Software development is an entire discipline within itself, but even comparatively simple smartphone apps that collect minimal data can be highly revealing of everyday behaviour. However, we face numerous challenges that go beyond technological development. Some of these issues pretain to theorising and replication, while others concern the scientific climate in which we operate. Most of these issues are not unique to research involving new technology, but they become more apparent as the speed of innovation accelerates. As a result, we appear to carry very little understanding forward to the next mass-adopted innovation.

By reflecting on past successes and failures, this chapter provides guidance on how psychological research can become more productive and break free from tired cycles of research. More importantly, if psychological science can re-align existing priorities and embrace the digital age, it has nothing to lose and everything to gain.

Chapter 1 has three goals. First, it provides motivation and history for the methodology by reviewing seminal insights and current debates about the relationship between language and thought, outlining how most research in this field concerns the structure of language rather than its use. Second, it outlines the scope for using CODA by identifying crucial and typical areas of application, with specific focus on mental representations and cognitive processes. Third, it highlights the scope and limits of language analysis of this kind, along with a discussion of reliability and generalisability of insights gained by using CODA. Altogether, the chapter provides in-depth insights into the foundational insights the method builds on, what it is intended for, why and where it is useful, and how it relates to other approaches to cognition.