An interesting article...

Cognitive Dissonance

Cognitive dissonance is a psychological phenomenon which refers to the discomfort felt at a discrepancy between what you already know or believe, and new information or interpretation. It therefore occurs when there is a need to accommodate new ideas, and it may be necessary for it to develop so that we become "open" to them. Neighbour (1992) makes the generation of appropriate dissonance into a major feature of tutorial (and other) teaching: he shows how to drive this kind of intellectual wedge between learners' current beliefs and "reality".

Beyond this benign if uncomfortable aspect, however, dissonance can go "over the top", leading to two interesting side-effects for learning:

if someone is called upon to learn something which contradicts what they already think they know — particularly if they are committed to that prior knowledge — they are likely to resist the new learning. Even Carl Rogers recognised this. Accommodation is more difficult than Assimilation, in Piaget's terms.
and—counter-intuitively, perhaps—if learning something has been difficult, uncomfortable, or even humiliating enough, people are less likely to concede that the content of what has been learned is useless, pointless or valueless. To do so would be to admit that one has been "had", or "conned".

Cognitive dissonance was first investigated by Leon Festinger and associates, arising out of a participant observation study of a cult (Dittos, Rush!) which believed that the earth was going to be destroyed by a flood, and what happened to its members — particularly the really committed ones who had given up their homes and jobs to work for the cult — when the flood did not happen. While fringe members were more inclined to recognise that they had made fools of themselves and to "put it down to experience", committed members were more likely to re-interpret the evidence to show that they were right all along (the earth was not destroyed because of the faithfulness of the cult members).

Note: See below