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Objectives: The Demand-Control (DC) and Effort-Reward Imbalance (ERI) models predict health in a work context. Self-report measures of the four key constructs (demand, control, effort, and reward) have been developed and it is important that these measures have good content validity uncontaminated by content from other constructs. We assessed relevance (whether items reflect the constructs) and representativeness (whether all aspects of the construct are assessed, and all items contribute to that assessment) across the instruments and items.Methods: Two studies examined fourteen demand/control items from the Job Content Questionnaire and seventeen effort/reward items from the Effort-Reward Imbalance measure using discriminant content validation and a third study developed new methods to assess instrument representativeness. Both methods use judges' ratings and construct definitions to get transparent quantitative estimates of construct validity. Study 1 used dictionary definitions while studies 2 and 3 used published phrases to define constructs.Results: Overall, 3/5 demand items, 4/9 control items, 1/6 effort items, and 7/11 reward items were uniquely classified to the appropriate theoretical construct and were therefore 'pure' items with discriminant content validity (DCV). All pure items measured a defining phrase. However, both the DC and ERI assessment instruments failed to assess all defining aspects.Conclusions: Finding good discriminant content validity for demand and reward measures means these measures are usable and our quantitative results can guide item selection. By contrast, effort and control measures had limitations (in relevance and representativeness) presenting a challenge to the implementation of the theories. Statement of contribution What is already known on this subject? While the reliability and construct validity of Demand-Control and Effort-Reward-Imbalance (DC and ERI) work stress measures are routinely reported, there has not been adequate investigation of their content validity. This paper investigates their content validity in terms of both relevance and representativeness and provides a model for the investigation of content validity of measures in health psychology more generally. What does this study add? A new application of an existing method, discriminant content validity, and a new method of assessing instrument representativeness. 'Pure' DC and ERI items are identified, as are constructs that are not fully represented by their assessment instruments. The findings are important for studies attempting to distinguish between the main DC and ERI work stress constructs. The quantitative results can be used to guide item selection for future studies. [ABSTRACT FROM AUTHOR]

Objectives: 'Habit' is a process whereby situational cues generate behaviour automatically, via activation of learned cue-behaviour associations. This article presents a conceptual and empirical rationale for distinguishing between two manifestations of habit in health behaviour, triggering selection and initiation of an action ('habitual instigation'), or automating progression through subactions required to complete action ('habitual execution'). We propose that habitual instigation accounts for habit-action relationships, and is the manifestation captured by the Self-Report Habit Index (SRHI), the dominant measure in health psychology.Design: Conceptual analysis and prospective survey.Methods: Student participants (N = 229) completed measures of intentions, the original, non-specific SRHI, an instigation-specific SRHI variant, an execution-specific variant, and, 1 week later, behaviour, in three health domains (flossing, snacking, and breakfast consumption). Effects of habitual instigation and execution on behaviour were modelled using regression analyses, with simple slope analysis to test habit-intention interactions. Relationships between instigation, execution, and non-specific SRHI variants were assessed via correlations and factor analyses.Results: The instigation-SRHI was uniformly more predictive of behaviour frequency than the execution-SRHI and corresponded more closely with the original SRHI in correlation and factor analyses.Conclusions: Further, experimental work is needed to separate the impact of the two habit manifestations more rigorously. Nonetheless, findings qualify calls for habit-based interventions by suggesting that behaviour maintenance may be better served by habitual instigation and that disrupting habitual behaviour may depend on overriding habits of instigation. Greater precision of measurement may help to minimize confusion between habitual instigation and execution. Statement of contribution What is already known on this subject? Habit is often used to understand, explain, and change health behaviour. Making behaviour habitual has been proposed as a means of maintaining behaviour change. Concerns have been raised about the extent to which health behaviour can be habitual. What does this study add? A conceptual and empirical rationale for discerning habitually instigated and habitually executed behaviour. Results show habit-behaviour effects are mostly attributable to habitual instigation, not execution. The most common habit measure, the Self-Report Habit Index, measures habitual instigation, not execution. [ABSTRACT FROM AUTHOR]