When queuing in a supermarket, who do you let go first?

Unlike cooperation among individuals that meet on a regular basis, one-shot interactions among strangers are not motivated by the prospect of receiving a favour in return. So why bother being helpful? In an attempt to shed light on the evolutionary puzzle of what factors result in cooperation among genetically unrelated individuals who meet only once, two German researchers examined a situation well-known to everyone: standing in line at the checkout of a supermarket. —> Read More