Because Marion thinks Peter is unfriendly, Marion has never waved or said hello to Peter when she sees him in the hall. Peter, who is shy, has not greeted Marion either. His lack of greeting has reinforced Marion's belief that he is unfriendly. It appears as if Marion's behavior has led to:

Self fulfilling prophesy.

Explanation:

Self fulfilling prophesy is identified to be a sociological term or prediction that happens when a false belief is seen to tend to affect a persons behaviour; here, the false behavioural attitude that sometimes makes itself true is seen to affect a persons behaviour the more.

Even in some situations, a person is seen to perceive these instances as evidence that you know yourself and your abilities quite well(which are true in some cases), without the person thinking about the effects it has on expectations have on your behavior.

A factor about this is that you sometimes find that you can sometimes be surprisingly accurate in your predictions.

For instance, you might predict that a project you are working on will turn out exceedingly well, and feel confident in your ability to foresee the future when your hard work pays off and your project is received positively.

Alternatively, you might expect that a speech you have to give at a work event will go terribly, and thus you feel no surprise when you stutter, mumble, and frequently forget your next point while speaking.