Causes and symptoms in preschoolers' conceptions of illness

The nature of children's concept of illness is of interest both to researchers in health psychology and to those studying naive theories of biology. Recent perspectives on conceptual development suggest that children's concepts are not always simpler versions of adults' concepts. Rather, children's concepts may have a variety of different structures. Two studies investigate whether preschoolers' (and adults') concept of illness has a nominal, cluster, or natural kind representation. Evidence for conceptual structure came from ascriptions of illness and from inferences about properties of illnesses. The roles of symptoms and underlying causes were investigated with respect to these judgments. Results suggest that adults' concept of illness has a property cluster (e.g., prototype) structure. Both causes and symptoms affected adults' categorization of illnesses, with neither type of feature being definitive. Adults did not see any features as universally or uniquely characteristic of illness. Children's ascriptions of illness generally matched adults'. However, children's inferences for some properties were highly correlated with judgments of illness. Thus, children may view illness as a richer source of inferences (and hence more like a natural kind) than do adults. Among the inferences explored were judgments of contagion. Children seemed to associate contagion with a particular type of causal process (infection) rather than with illness per se. Results are discussed in terms of their implications for accounts of children's biological knowledge.