What collective behaviour means

1. A crowd is not just a lot of individuals standing near each other, because being in one changes what each person is willing to do.
2. Two things do most of that work, the way a crowd hides you and the way a crowd sets a norm for everyone in it.
   1. Being hidden is deindividuation, the loss of your sense of being a separate, identifiable person, and it loosens the self-control that normally holds your behaviour in place.
   2. The norm is whatever the crowd around you appears to be doing, and it quietly tells you what counts as acceptable here.
3. Neither of those is good or bad on its own, which is why collective behaviour can run in two completely opposite directions.

When crowds behave pro-socially

1. A shared purpose
   1. When a crowd has gathered in order to do something good, such as a charity walk or a clean-up of a local park, the norm on offer is a helping one and people fall in with it.
2. A visible model
   1. One person openly helping shows everyone else that helping is what is done here, and the behaviour spreads through the crowd quickly.
3. A sense of being one group
   1. Losing your separate identity does not only remove restraint, because it can also replace your own goals with the crowd's, and a stranger in the crowd starts to feel like one of your own people worth helping.

When crowds behave anti-socially

1. Anonymity
   1. In a large crowd you are unlikely to be picked out or named, so the fear of being blamed that usually restrains you is much weaker.
2. A hostile norm
   1. If the people around you are shouting abuse or damaging property, that becomes the visible standard for the group, and joining in feels less like a decision than like keeping up.
3. Responsibility spread thin
   1. When hundreds of people are present, no single person feels that stopping the trouble is their job, so the harmful behaviour continues unchallenged.

Evidence from Haney, Banks and Zimbardo

1. Haney, Banks and Zimbardo (1973) selected 24 men who had been screened as normal and healthy, of whom 22 took part, and assigned the roles of guard and prisoner at random.
   1. Prisoners were given a smock and an ID number rather than a name, and the guards worked as an anonymous group, so almost everything that marked either side out as an individual was removed.
2. The guards' verbal aggression escalated day by day and was worst when they were away from surveillance, which is exactly what you would expect if anonymity is what loosens restraint.
3. Five prisoners were released early and the study was stopped on day six of a planned fourteen.
4. The careful screening and the random allocation are what make the study useful here, because they rule out the argument that these particular men were simply cruel to begin with.
   1. Even so, not all of the guards were cruel and about half the prisoners lasted the whole study, so individual differences survived the situation rather than being wiped out by it.

Turning this into marks

1. Name the mechanism, such as anonymity or the crowd's norm, and then say what it does to behaviour.
2. Cover a pro-social case as well as an anti-social one, because an answer about harm alone is half an answer.
3. The mark most often lost is leaving the crowd in the source unnamed, so say which crowd it was and what it was doing.