The primal instinct to selfishly flee from a dangerous situation takes precedence over helping others - unless you have time on your hands, according to Australian researchers.
Professor Benno Torgler, of the Queensland University of Technology in Brisbane, and colleagues, report their work in this week's Proceedings of the National Academy of Sciences.
Torgler and colleagues compared the behaviour of individuals on the ill-fated R.M.S. Titanic and R.M.S. Lusitania passenger ships.
They found that the social norm of "women and children first" was deferred to only on the Titanic, where first class passengers also had a higher probability of survival.
In contrast, the situation on the Lusitania favoured survival of the fittest.
"There were substantial behavioural differences on the Lusitania," says Torgler of QUT's School of Economics and Finance.
"Those with the best chance of survival were aged 16-35 with little difference between genders (10.4% females versus 7.9% for males) and first class passengers actually fared worse. This suggests that competition was the strongest driving factor influencing survival".
The Titanic and Lusitania were chosen for the study because of the availability of individual passenger crew data, the similar passenger demographics and the historical timing of the disasters.
"The similarities between the two vessels are uncanny," notes co-author David Savage.
"The mean survival rate, age, proportion of women, and classes of passengers is almost identical. And given that the two events occurred within a couple of years of each other (the Titanic in 1912 and the Lusitania in 1915), we can also assume that the social norms or manners were unchanged", he says.
What differed between the two events was time.
The Titanic took 2 hours and 40 minutes to sink after its collision with an iceberg, whereas the Lusitania was completely submerged 18 minutes after being hit by a German U-boat.
"The shortened disaster time favoured instinctive fight-or-flight behaviour, whereas the lengthier disaster led to the appearance of social norms. We know the first is driven by the rush of adrenaline to the brain, but we don't know exactly when the altruistic behaviour takes over," says Torgler.
"These are true preferences revealed only in test conditions, they aren't something you can accurately assess by surveying responses to hypothetical situations".
Previously, the researchers had noted that British passengers on the Titanic were less likely to survive than all other nationalities.
"This had suggested that English manners were a disadvantage in a life and death situation; but on the Lusitania, these cultural differences didn't seem to make much difference to a passenger's chance of survival", says Savage, adding that this is the subject for another paper.
The group are now looking at human behaviour in risky activities in which people choose to partake, such as mountaineering, as well as other tragedies like 9/11 and the Australian bushfires.
Knowing how individuals and groups make decisions helps to shape policy for disaster situations.
"There's a fine line between crowding out naturally good behaviour and creating policy that has a positive impact on survival outcome," adds Savage.