Health Psychology. Michael Murray
Dissatisfied
5–9 Extremely dissatisfied
Is there any basis for assuming the total scores on the SWLS are measures of a quantitative attribute ‘Life Satisfaction’ such that there is an absolute zero (as there would be in any ratio scale) and a person with a score of 20 has exactly double the life satisfaction of a person who has a score of 10 and/or that two people with scores of 30 and 25 have a life satisfaction that is the same ‘distance’ apart (5 points) as in the case of two people with scores of 20 and 15? If the 5-point differences were shown to be the same, then the SWLS would be an interval scale. However, neither of the hypotheses is plausible. We can only infer a person’s life satisfaction from their answers to items on the SWLS. This is because we have no independent definition of life satisfaction, and no evidence that life satisfaction is a quantitative attribute, apart from the SWLS scores themselves.
The total scores on the SWLS really only allow respondents to be placed along an ordinal scale, yet it is common practice to treat the scores as if they were interval scale data that can be added together, subtracted, averaged and compared between groups using standard deviations and variance scores in statistical analyses.
This measurement problem cuts through the entire discipline of psychology. We infer or, in truth, are forced to act on the unproven assumption (i.e., prejudice) that a person’s score on a questionnaire is a measure on a continuous quantitative interval scale. That assumption has never been tested and psychometrics, therefore, has been challenged as a form of ‘pathological science’ (Michell, 2008).
[Nobody promised you a rose garden! We said at the outset that we would adopt a critical stance, and the measurement problem we have described here, which, for obvious reasons, is not normally talked about, is a good start. The situation is not completely hopeless, however, so please do read on.]
Fortunately, for a practical domain like health psychology, it is possible to ‘get by’ without any proper solution to the measurement problem. Yes, it’s a fudge, but a necessary fudge, because otherwise psychological science would be no more advanced today than it was in 1900. One of the main goals of health psychologists is to design interventions that are effective solutions to health problems. Normally we can find ways to objectively compare different interventions to see what works and what doesn’t work. The associations between interventions and outcomes can be observed and measured in quantitative terms. Additionally, a patient seeking treatment for an unpleasant condition can express their thoughts, feelings and motives using plain words by answering questions or items on a questionnaire. In the vast majority of cases, either psychological measures are assumed, for the sake of convenience, to lie along an interval scale or the data are purely categorical.
Health psychologists are concerned with patient–practitioner interactions, public health promotion, or working in communities where actions are carried out, all with observable inputs and outputs. Outcomes in these various scenarios are all objectively observable and measurable, even if the measurements themselves are not shown to have an underlying quantitative attribute. In addition, it is the experiences of the actors that are important, and these are amenable to qualitative methods where the presumption of quantitative attributes and the associated measurement problem do not apply.
A Framework for Health Psychology
Theoretical thinking in any scientific discipline consists of four broad types that vary according to their level of generality: paradigms, frameworks, theories and models. Paradigms explicitly state assumptions, laws and methods in a complete system of thinking about a field of inquiry (Kuhn, 1970). Frameworks have some of the characteristics of paradigms, but are smaller-scale and much looser, although they are a way of organizing information about a field. Figure 1.5 shows a framework about the main influences on the health of individual human beings that we find quite helpful. It has been adapted from the work of Dahlgren and Whitehead (1991) and we call this the ‘Health Onion’.
Figure 1.5 The ‘Health Onion’: a framework for health psychology
Source: Dahlgren and Whitehead (1991)
The ‘Health Onion’ has a multi-layered structure of ‘rings’, with the individual person at its core, surrounded by four layers of influence,‘systems’ or ‘rings’
Core: age, sex and hereditary factors (Part 1 of this book).
Level 1: individual lifestyle (Part 2 of this book).
Level 2: social and community influences (Part 1 of this book).
Level 3: living and working conditions, and health care services (Parts 3 and 4 of this book).
Level 4: general socio-economic, cultural and environmental conditions (Part 1 of this book).
The Health Onion is a systems framework with seven characteristics:
1 It is holistic – all aspects of human nature are interconnected.
2 It is concerned with all health determinants, not simply with events during the treatment of illness.
3 The individual is at the core with health determinants acting through the community, living and working conditions, and the socio-economic, cultural and physical environment.
4 It places each layer in the context of its neighbours, including possible structural constraints upon change.
5 It has an interdisciplinary flavour that goes beyond a medical or quasi-medical approach.
6 It makes no claim that any one level is more important than others.
7 It acknowledges the complex nature of health determinants.
Different theories and models are needed for each setting and context. However, there is also a need for a general paradigm for individual health within which specific theories and models can be nested. Such a paradigm should attempt to represent in an explicit, detailed and meaningful way the constraints upon and links between individual well-being, the surrounding community and the health care system (Marks, 1996). No such general paradigm exists. We are waiting for a Hippocrates, Darwin or Einstein.
BOX 1.6 Filtering of evidence in evidence-based practice
Some methodological purists believe we have a paradigm for all of health care in the form of evidence-based medicine or evidence-based practice (EBP). In EBP, randomized controlled trials are used to produce conclusions about the effectiveness of different methods and treatments. In theory, the approach sounds wonderful. In practice, it is far from perfect. Evidence on effectiveness in EBP is assumed to have an objective, inviolable status that reflects ‘reality’. It is given an iconic status. In some undefined ways, this evidence about ‘reality’ not only aids decision-making, but also determines it. In truth, evidence is never absolutely certain. It rests on subjective elements consisting of negotiable, value-laden and contextually dependent beliefs that are given the status of ‘facts’ when all they really are items of information. Until the Magellan–Elcano circumnavigation of 1519–22 the Earth was assumed by everybody to be completely flat. The flat-Earth was a belief masquerading as fact. Flat-earthers still exist, but their numbers are dwindling.
The nature of evidence, and the methods by which evidence is gained, are contentious issues in the history of science. In health care, evidence (= new knowledge) for a technique or treatment is not an accident, but the product of a series of ‘gates’ or ‘filters’ that must be passed before the technique is deemed to be useful.
Consider the sequence of processes through which evidence must pass if it is to be considered admissible in EBP. The filtering is so selective that, typically, systematic reviewers will be able to find only a dozen or fewer primary studies that fulfil the inclusion criteria from a field of several thousand. It’s not unlike making a pot of filter coffee