Intelligence, religious and political beliefs are connected to the accuracy of UK adults' population estimates

British people tend to overestimate the prevalence of different minority demographics, beliefs, and behaviors among the public, according to a study publishing December 22 in the open-access journal PLOS ONE.

Adrian Furnham at the Norwegian Business School in Oslo, Norway, and colleagues, asked 573 U.K. adults to make population estimates for the U.K. for each of 25 different characteristics, including socioeconomic, religious, health, and behavioral traits. Participants were also asked to complete an intelligence test and to rate their own religiousness, political beliefs, and optimism. They found that the accuracy of estimates was generally low, but respondents were most accurate for the prevalence of vegetarianism, car ownership, and voting. Estimates were least accurate for the proportion of the population who identify as homosexual, which was overestimated by 10% on average, while participants tended to underestimate the percentage of adults claiming state benefits.

Accuracy was significantly correlated with respondents' religiousness, political orientation, and intelligence but optimism did not seem to play a significant role. Incorrect guesses were more likely to overestimate than underestimate the true size of minority groups, and the tendency to exaggerate was strongly related to religious and political attitudes. People were most likely to exaggerate estimates relating to minorities, whereas estimates of affluence and education were less associated with ideology. The researchers found that nationality, sex, religiousness, intelligence, number of children, occupation, and political views were significantly correlated with the magnitude of an individual's estimate; together these individual differences accounted for 12% of the variation between respondents.

Although the study sample was not fully representative of the British population, the results suggest that the statistics people read and remember are biased by their existing beliefs. Perceptions of issues relating to welfare benefits and minorities appear to be particularly prone to bias, which the authors suggest may be related to feelings of social competition.

The authors add: "The study shows that people are generally quite inaccurate about social and demographic statistics of their own society. There is a clear tendency, for example, to overestimate minorities. The tendency to overestimate is related to IQ levels and a sense of being threatened."