"Women and children first!" may be a sentiment that was laudably practiced during the evacuation of the RMS Titanic, but that kind of selflessness is not the norm in most disasters at sea, according to a new study.

Swedish researchers examined 18 maritime disasters that occurred around the world over three centuries, from the grounding of the HMS Birkenhead in 1852 to the 2011 sinking of the Russian cruise ship MV Bulgaria. They were looking for signs that men consistently give up their seats on lifeboats. But as their paper in the Proceedings of the National Academy of Sciences shows, chivalry turns out to be a rare virtue at sea.

Overall, male crew members have the highest survival rate during a maritime accident, followed by male passengers and ship captains. Women had a survival rate that was only half that of men's, on average, while children fared the worst.

The sex gap in survival rates has decreased since World War I, the authors noted.

Given these figures, the Titanic stands out conspicuously - it was a disaster where the survival rate of women was three times that of men. Titanic was also one of only five ships in the study where the captain specifically ordered that women and children should be seated on the lifeboats first (some reports also say that the crew of the Titanic shot at men that disobeyed captain's order).

"Most notably, it seems as if it is the policy of the captain, rather than the moral sentiments of men, that determines whether women are given preferential treatment in shipwrecks," the authors wrote.

The researchers say that they found no link between how quickly the ship sunk and how men behaved. Nor did other contextual factors, like the length of the voyage, help or hurt the survival rate for women.

"On the basis of our analysis, it becomes evident that the sinking of the Titanic was exceptional in many dimensions and that what happened on the Titanic seems to have spurred misconceptions about human behavior in disasters," the authors wrote.