Islamic etiquette holds that in any encounter the first person to say Salaam gets a multiple of the blessings that the person who is being addressed receives when he replies.
This is interesting because since Salaam means peace, it's clear that the first person in the encounter who makes their intentions known to the other party is the one who is doing the most to promote co-operation - since it is they who are removing any doubt that the encounter will be peaceful.
Robert Axelrod in his work on game theory (The Evolution of Co-operation) sets the following criteria as the ones which promote co-operation,
- being clear,
- retaliating and
- being forgiving.
Being the first to say salaam makes the individual's co-operative intentions clear and thus promotes co-operation on the part of the other party.
Islam also sets clear guidelines for retaliation should co-operation not be forthcoming, and the other party seeks to take advantage of those with peaceful intentions. The religion also sets the penalties for infringing on the rights of others - and thus makes clear to others that Muslims will not be the first to instigate aggression.
Game theorists recognise that being clear about a willingness to retaliate actually promotes peace, because the other party knows that there will be a penalty to pay for aggression.
However, in Islam forgiveness is also considered important, since it gives the other side an opportunity to behave in a more co-operative manner in the future.