Introduction

Health cognitions are items of knowledge or beliefs about health and illness. These include evaluations of health-relevant behaviours, expectations about the consequences of these behaviours, self-representations, perceptions of social approval or disapproval resulting from engaging in these behaviours, perceptions about the behaviour of others, perceptions regarding one's own abilities and thoughts about ones personal disposition towards engaging in particular behaviours. The assessment of health cognitions is more than merely the rule-based assignment of numerals to objects or events. Assessment must assign values to entities that are theoretically meaningful, and in this respect assessment and theory go hand in hand. Theory provides us with guidance as to what we should measure, but it is good measurement that theory depends upon.

Self-report methods for assessing health cognitions

Health cognitions are commonly assessed by self-reports measured using Guttman, Thurstone, Likert, or semantic differential scales (Kline, 2000), although only the latter two continue to receive significant attention. Likert scales are less cumbersome than Thurstone's technique without compromising on reliability and validity. Semantic differential scales consist of bipolar adjective scales where respondents are asked to rate an attitude object (e.g. ‘Exercising for 30 minutes, 5 times a week would be …’ Good–Bad). Unlike other techniques, semantic differential scales do not require the development and scaling of specific belief items (see Eagly & Chaiken, 1993).

Important considerations for self-report measures

Since good theory depends upon dependable measurement, it is disappointing that much published work examining health cognitions pays scant attention to reliability and validity.