"These results provide compelling evidence that optimism is a universal phenomenon," said Matthew Gallagher, a psychology doctoral candidate at the University of Kansas and lead researcher of the study.
Optimism was highest in Ireland, Brazil, Denmark and New Zealand. It was lowest in Zimbabwe, Egypt, Haiti and Bulgaria. The United States ranked 10th among the 140 countries.
In suggesting that humans are optimistic by nature, the new study from the University of Kansas reinforces previous studies that found optimism to be a common human trait. Optimism also tends to increase with age.
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