When there’s only one person around in a situation, they’re much more
likely to lend assistance to people in need, whether it’s to help pick
up something they have dropped or something more important like help
them when they are hurt.

When there’s a group of people, though, no one acts. They all expect someone else will do it, so no one volunteers or pauses.

The
Asch conformity experiments were a series of studies published in the
1950s that demonstrated the power of conformity in groups. These are
also known as the "Asch Paradigm" and proved that people will conform to
a groups opinion even if it conflicts their own.

This has a
profound effect when it comes to public opinion on such issues as war,
corruption, conspiracy (fact) theories and even what happened on 9/11,
since the majority of people watch main stream media television, and the
social conformity will be based on what they see on the news often
bypassing their own opinions so as not to be the outcast.