We are programmed to behave according to the rules of our closer or wider community. Even without noticing it, we are following behaviour patterns that are deeply rooted in the norms and values of our social reference groups. This is called social conformity.
What happens if a new person arrives at a group? How quickly do we learn what is expected of us? How soon do we start to conform? I have just seen an interesting experiment done by National Geographic. They sounded a beep in a crowded waiting room and the rule was to stand up after the sound. When a new "patient" arrived, it took only three trials before she started to obey the rules (without even knowing WHY the others were doing it).
Watch this funny video about the experiment: