Not good news for shy folks :o But conclusive testing on homo sapiens, rather than rats, would determine this issue once and for all.
The meek shall inherit a shorter lifespan, Tim Radford
The Guardian, 9 December 2003
It doesn’t pay to be shy, as research has shown that timidity could seriously shorten your lifespan - at least if you are a rat.
Sonia Cavigelli and Martha McLintock of the University of Chicago report in the Proceedings of the National Academy of Sciences that rats with neophobia, or fear of the unfamiliar, are 60% more likely to die at any time than bolder ones.
The research could also offer a guide to human behaviour. At 14 months, some human babies show signs of shyness, inhibition and fearfulness that correspond with more active endocrine and autonomic nervous systems. The Chicago team decided to explore this connection between fear and physiology in animals with much shorter lifespans and less complicated behaviour: laboratory rats.
They placed 28 young male rats in a tank into which various unfamiliar objects were introduced - a bowl, an empty food hopper, a tunnel and a brick - and watched their reactions. They found that some males cheerfully stepped out into their new surroundings while others remained hunched in fear. According to their behavior, the rats were classified as either neophobic or neophilic - novelty-loving.
The researchers found that both groups developed diseases, but the novelty-loving ones consistently survived longer.
The median lifespan for neophobes was 599 days compared with 701 days for the less frightened ones. All the neophobic males were dead by 840 days, whereas the oldest of the neophiles hung on for another six months.