The 22 degrees of happiness

You are at your friendliest and happiest when the temperature is 22 degrees Celsius.

A new study suggests that people living in places where the temperature is always mild - 22ºC, to be precise - are friendlier, more outgoing and emotionally stable.

Researchers at Beijing's Peking University believe that personalities may be shaped by the climate.

Analysing data from more than 1.6 million people in China and the US, the researchers discovered that 22ºC was the best temperature for happiness.

Despite differences in gender, age, average income and culture in these two countries, wherever the temperature is 22ºC, people are generally "more agreeable, conscientious, emotionally stable, extroverted and open to new experiences", the study found.

"Our findings offer insights into why people in different regions of the world exhibit different personality traits and behaviours. As climate change continues across the world, we may also observe concomitant changes in human personality," the researchers said in their paper, published in the Nature Human Behaviour journal this week.

Chris Hani Baragwanath Academic Hospital principal psychologist Jasmin Kooverjee could not comment on the reliability or validity of the study, but said people were more relaxed when they were comfortable.

"An average temperature of 22 [degrees] means it is comfortable. It is not too hot or cold. When people are comfortable, they are actually friendly because they are more relaxed."