This occurs because of attribution on two counts:
I. Fundamental attribution error: the tendency to underestimate the influence of external factors and overestimate the influence of internal factors when making judgments about the behavior of others.
II. Self serving bias: the tendency for individuals to attribute their own successes to internal factors while putting the blame for failures on external factors.
1) Distortions: distortion occurs when we twist and manipulate events either consciously or unconsciously. We often tend to distort reality when it is unfavorable to us, because it threatens our self-image. We then act in a defensive manner and distort or even totally shut out what is actually occurring. In other words, we tend to twist or avoid that which is an unpalatable threat to our ego. Thus, distortion is due to defense mechanisms that operate when on e encounters data or receives information that is incongruent with one's self-concept.
2) Self-fulfilling prophecy: this denotes a tendency to find in a person, situation, or even in one's own self, what one anticipates or expects to find, in other words, what we perceive could be governed by what we expect or believe to be present. For example, if a person thinks he is no good in statistics and will not do well in the exam, and if in fact he did poorly, he would tell himself, that he did poorly because he was no good at the subject, in another instance, if a person is convinced that managers have to talk assertively to be effective, and that women by nature are not so and are lacking in strong leadership, he will then tend to focus attention on how forcefully a woman manager puts forth her points of view.