Be careful what you promise people. You are not just obliging yourself to keep your promises; other people will hold you to account for them as well.

Dutch-sponsored researcher Manuela Vieth investigated how the behaviour of other people and one's own behaviour influences later behaviour.

The punishing of bad behaviour and the rewarding of good behaviour are patterns of behaviour which help to maintain the social order. Yet according to some researchers, the rewarding of good behaviour, positive reciprocity, is non-existent or virtually non-existent. Vieth's results have now shown them to be wrong.

Social experiments involving trust

To investigate how people allow themselves to be influenced by their own and other people's previous behaviour, Vieth had subjects make decisions in different choice situations. The emphasis was on trust situations and similar interactions in which proceeds could be shared. In some choice situations participants could reward trustworthiness and in others they could promise rewards or threaten with penalties.

Depending on their behaviour, participants earned more or less money. People could earn more money by betraying trust than by rewarding trust. Punishing or rewarding also cost money. These choice situations were played out one-on-one with anonymous partners. Interactions were not repeated with the same people, so emotional ties and potential future benefits played no role in the behaviour.

When one player indicated that he trusted the other, the other person actually appeared to become more trustworthy. Conversely, when someone promised to be trustworthy, the other person also trusted him more. But promising to be trustworthy also increases your own trustworthiness. With these results, Vieth shows that feelings of obligation and people's urge to be consistent in their behaviour can ensure that people keep their word.

Punishment and rewards

Vieth found that the breaking of promises of trustworthiness leads to revenge. Betrayal of trust after a reward for trustworthiness had been promised was also punished severely. Feelings of indignation therefore seem to have a marked influence on later behaviour. The fulfilment of promises was valued less highly, however. Friendly behaviour after the granting of favours led to weaker feelings of obligation than the original favours.

The money, however, had only a limited influence on the decisions to punish or reward. Only one person voluntarily accepted the costs of reducing or increasing the other person's results in situations which had not been preceded by an unfriendly or friendly decision of the other person. The behaviour therefore appeared to be guided primarily by feelings of indignation or obligation and by the tendency to behave consistlently.

Source: NWO