Intuitive Judgments of Rate Change: The Case of Teenage Pregnancies

Three studies examined intuitive judgments of rate change. These studies considered how people intuitively decide that the occurrence rate of particular events is on the increase or in decline. Using the topic of teenage pregnancy, participants were given information about the population size and the frequency of pregnancies at a hypothetical high school in three studies at two points in time. In the first of these studies details about population size were made highly salient, and here population information was found to directly influence intuitive judgments of rate change. In the second study population information was presented in a more realistic fashion. Under these conditions judgments that the pregnancy rate had changed were found to be based on changes in the number of pregnancies. Whenever the number of pregnancies changed, regardless of compensating changes in school size, people inferred a change in rate. In the third of these studies, population details were not provided; only information about number of pregnancies was presented. Subjects' queries for additional information were then assessed. Despite the absence of population information, few subjects requested population details when asked what additional information they would like in order to judge the relative seriousness of the pregnancy problem. Taken together, the three studies suggest that when making intuitive judgments of change in rate, people may be relatively insensitive to the importance of population information. The implications of such findings are discussed.