Molecular genetics is corning to play an increasing role in biomedical understanding of common diseases. The implication of genetic findings is that at-risk individuals may be offered predictive genetic tests. How do individuals make decisions about predictive tests? Richards (1993) argues that the first step in understanding how people make these decisions is to investigate lay beliefs of genetics.
The first aim of this thesis was to examine lay representations of genetics. As such, the first study in the thesis examined representations of genetics in a sample of 72 first year undergraduate students. Through content analysis of open-ended questionnaires, it was discovered that respondents' representations of genetic diseases consisted primarily of causal
explanations of such diseases. Three mental models of inheritance were inferred from participants' representations of inheritance. Additional representations centred on the identity, consequences, and treatment of genetic diseases. A cohort study of 268 undergraduate participants examined whether representations of genetics varied over one and a half years. Very few differences were found between the cohorts. Representations of genetics also did not seem to be a function of the demographic variables that were measured.
The second aim of the thesis was to describe how individuals make decisions to pursue predictive genetic testing. Two vignette studies were employed to assess participants' decisionmaking behaviour. In the first study, 115 undergraduate respondents were presented with a hypothetical predictive testing scenario. A range of decisions were elicited; similarly, there was a wide range of responses to the scenario. In the second study, information was made available
for 20 participants, recruited from the general public, to access via a computer package. Analysis of verbal protocol and information acquisition data demonstrated that participants went through an iterative process of accessing and evaluating information until they reached a final decision.
Using a nomothetic approach, an evaluation of the consequences of the various options was the most prevalent decisional strategy. An idiographic approach, however, revealed that individuals made their decisions in a variety of decision-making styles.
The final aim of the thesis was to explore the role of lay beliefs of genetics in the decision to pursue predictive genetic testing. Using a nomothetic approach, little correspondence was found between participants' representations of genetics and their decision making. Using an idiographic approach, however, individuals' representations of genetics seemed to be influential in some people's decision making. For a large number of participants, however, it was difficult to assess
whether their representations of genetics had a bearing on their decision making.