Extroverts are better able to fight disease, a new study from researchers at the University of Nottingham and the University of California indicates.
Researchers looked at 121 healthy adults between the ages of 18-59 and found that extroverts had stronger immune systems than those who are more cautious.
As lead author Professor Kavita Vedhara explains, this could be because of personality rather than biology - extroverts are more sociable so might be exposed to more infections.
"Individuals who may be less exposed to infections because of their cautious/conscientious dispositions have immune systems that may respond less well. We can't, however, say which came first," she said.
Professor Vedhara added in an email interview with i100.co.uk that the data came with a caveat.
"Our data actually suggest that extroverts have an immune system that we would expect to respond well to infection, whereas conscientious people do not.
"So we might expect that conscientious people have less effective immune systems. However, that is only what we would predict from our results. We did not, in this study, actually test how well the immune system responds to infection - but just looked at the expression of genes that orchestrate this response," she said.