From “A theory of social comparison processes,” by L. Festinger, 1954, Human Relations, 7, 117-140

1. There exists, in the human organism, a drive to evaluate his opinions and his abilities.
2. To the extent that objective, nonsocial means are not available, people evaluate their opinions and abilities by comparison respectively with the opinions and abilities of others.
3. The tendency to compare oneself with some other specific person decreases as the difference between his opinion or ability and one's own increases.
4. There is a unidirectional drive upward in the case of abilities which is largely absent in opinions.
5. There are nonsocial restraints which make it difficult or even impossible to change one's ability. These nonsocial restraints are largely absent for opinions.
6. The cessation of comparison with others is accompanied by hostility or derogation to the extent that continued comparison with those persons implies unpleasant consequences.
7. Any factors which increase the importance of some particular group as a comparison group for some particular opinion or ability will increase the pressure toward uniformity concerning that ability or opinion within that group.
8. If persons who are very divergent from one's own opinion or ability are perceived as different from oneself on attributes consistent with the divergence, the tendency to narrow the range of comparability becomes stronger.
9. When there is a range of opinion or ability in a group, the relative strength of the three manifestations of pressures toward uniformity will be different for those who are close to the mode of the group than those who are distant from the mode. Specifically, those close to the mode of the group will have stronger tendencies to change the positions of others, relatively weaker tendencies to narrow the range of comparison, and much weaker tendencies to change their position compared to those who are distant from the mode of the group.