Perceived severity (also called perceived seriousness) refers to the negative consequences an individual associates with an event or outcome, such as a diagnosis of cancer. These consequences may relate to an anticipated event that may occur in the future, or to a current state such as a pre-existing health problem.
The concept of severity as an important determinant of behaviour has appeared in a number of theories and across different academic disciplines, albeit under a more general name. Within economic theory, the concept of ‘utility’ has been used to understand behavioural choice (e.g. consumer decision-making) where utility refers to the value placed on an object or outcome. Within psychology the concept of ‘valence’ was developed to explain behavioural motivation (Lewin et al., 1944), the hypothesis being that people would avoid areas of negative valence and move towards areas of positive valence. Although these economic and psychological theories developed independently, the similarity between the concepts of utility and valence has been noted (Edwards 1954).
Severity can be seen as an example of negative utility and negative valence; however, the specific term appears to have its roots in the Health Belief Model (HBM). According to Rosenstock (1974) the HBM draws heavily on the psychological literature and the behavioural motivation theory of Lewin (Lewin et al., 1944). Lewin proposed that behaviour depends on two variables: 1) the value an individual places on a particular outcome, and 2) the likelihood that an individual will be successful in achieving their goal (‘expectancy’). Together, these two factors comprise the central components of 'expectancy-value' theories.
As with severity, the concept of expectancies has also appeared across a number of different disciplines and theoretical models (Feather, 1959; Maiman and Becker, 1974), and a number of theories used to understand health behaviour are classified as expectancy-value theories, including the Health Belief Model (HBM) (Hochbaum, 1958; Maiman and Becker, 1974), Protection Motivation Theory (PMT) (Rogers, 1975; Rogers, 1983), the Extended Parallel Process Model (EPPM) (Witte, 1992; Witte, 1998), the Theory of Reasoned Action (Fishbein and Ajzen, 1975) and the Theory of Planned Behaviour (Ajzen, 1985). Although these models differ in the types of behaviour they were developed to explain, the variables they include, and how the variables are thought to combine to predict behaviour or behavioural intentions, they all contain concepts that concern the evaluation or value attached to events or behavioural outcomes.