Clever people are more trusting than their less intelligent counterparts, researchers have claimed.
Those who are smarter than most may be better judges of character, they said. That group may also be more trusting of other people because they are better at weighing up situations, according to research from academics at Oxford University.
The study, published in the journal PLOS ONE, examined data from an American social attitudes survey.
It also found that people who are more trusting are more likely to have better health and greater happiness.
But the links between trust and health, and between trust and happiness, are not explained by intelligence, they added.
"Intelligence is shown to be linked with trusting others, even after taking into account factors like marital status, education and income," said lead author Noah Carl, from Oxford University's Department of Sociology.
"This finding supports what other researchers have argued, namely that being a good judge of character is a distinct part of human intelligence which evolved through natural selection. However, there are other possible interpretations of the evidence, and further research is needed to disentangle them."
Professor Francesco Billari added: "People who trust others seem to report better health and greater happiness.
"The study of social trust therefore has wider implications in public health, governmental policy and private charity, and there are good reasons to think that governments, religious groups and other civic organisations should try to cultivate more trust in society."
The academics analysed data from the General Social Survey, which is conducted every one or two years.
The survey, which has been running since the early 1970s, examines peoples' social status, their behaviours and social attitudes as well as intelligence.
The researchers found a strong correlation between trust and intelligence.
"One explanation is that intelligent individuals are better at evaluating others' trustworthiness, meaning that they tend to select into relationships with people who are unlikely to betray their trust," they wrote.
"Another possible explanation is that intelligent individuals are less likely to trust people to do things that someone being trusted might have a strong incentive not to do (e.g. repay a large sum of money). In other words, they may be better at identifying when any particular person would be likely to act untrustworthily, based on the characteristics of the prospective interaction (e.g., material payoffs, discount rates).
"Alternatively, it may simply be that intelligent individuals have a greater chance of interacting with people who are materially better-off, and who therefore have less to gain from acting untrustworthily. However, this seems quite implausible given that the relationship is robust to controlling for a great many different indicators of socio-economic position."