How Attitude Affect Behavior?

The question would have been, How does instead of When does....

Well, no offence here though attitude always is the representer of a person's behaviour, many fake it and many have it naturally. The way you carry yourself is the way you make other's create perceptions about you.... That's it....

A person’s behaviour changes when what he is exposed to changes. Meaning, a person’s behavioural pattern changes depends on his environment, his experiences and his disagreement with others. One of the main factors influencing behavioural patterns is the society people live in. Behavioural changes is often related to the Principal of Consistency where people expect everything in their minds to be constant and never changing and different information are always agreeing with each other. But disagreements do happen occasionally and the brain goes into a state of dissonance. Dissonance happens when two pieces of information disagrees with each other. Generally, people dislike being in a state of dissonance and so, they will work towards solving the problem and with this, their behaviour may change.
A good example of dissonance is where your friend may disagree with you in something and in a situation where your friend is a good thing but his disagreement is not, the two subjects cannot possible relate to each other and this causes dissonance. One of the simpler ways of resolving this issue is a change in opinion or behaviour towards one of the items in question. This means that if you change your opinion towards the subject or your friend into good or bad, the dissonance will no longer exist. The same applies if your friend changes his opinion towards you or the subject.
Another way to resolve this matter is when you justify your disagreement with a reason. Like how the subject may have a weakness or is vague or your friend may not be at his best at the time. But this form of rectification can only work when you truly believe in the reason you have.
Since a person’s attitude and behaviour are different, a reason can be created even when the person does not believe in it. This is done to give the impression of not being in a state of dissonance to others. This, however, is only temporary and the dissonance still exists and that person’s opinions must still change to resolve this problem. These are of course just examples and in truth, attitudes and opinions do not change as easily. The difference in changes for example, is affected by the importance of the subject matter and when something that is of less significance threatens to break the positive bond towards something that is much more important, the one that is more important is usually left unaffected.
There can also be dissonance between attitude and behaviours where a person does not agree with his or her own attitude. That person will then work towards creating a balance between the two.