When people observe kindness or generosity, they may be subtly pressured to look good and be more giving themselves. But this is just one of the minor reasons, as many act in an anonymous manner.

Seeing the other person being kind, people get to unconsciously copy their behaviour as the prosocial desire for goodness is rekindled.

• Women seem to be affected (or motivated) more than men by the kind behaviour of other people.
• A kind act on the street, or on TV had the same effect on people.
• The kind of kindness witness related to the response of the witness. If the act was praising, for instance, the r...