We only remember as few as 5% of our dreams, but do they have a role beyond surreal experiences during the night? The reason for dreaming that believe depends on your background in psychology...
Reading into Dreams
Freud supporters would say that dreams are an outlet for the sub-conscious, and the repressed emotions from childhood that lie there. A bad relationship or loss of a close one during childhood, for example, can be repressed, and the anger for the loss might be redirected towards the 'inner self', and only emerge during dreams or through regression. Freud's theories are difficult to prove, but, while they can not be disproven, they are very popular among many psychologists, and the relevance of some dreams to our lives would indicate that they are of some significance.
Dreaming for Survival
Another theory for dreams is that they play an important role in helping us, or at least, some animals, to survive. Dreams offer an opportunity for us to process our experiences from the previous day, and, by comparing them to past experience, formulate a stategy for survival that may be useful during the day. Of course, this theory is quite contrived and as difficult to prove as Freud's, and if dreams really are so important, why do we only remember a tiny proportion of them? Nevertheless, research has given some support to Winston's 'Survival Strategy' theory, as people deprived of REM sleep (the part in which dreams occur) have experienced serious side effects.
An Opportunity to Take Account
Crick and Michison suggested that dreams and nightmares offer the opportunity for us to 'reverse learn' and again process our experiences. By processing useless information, we 'clean up' our neuronal network (ie synapses) making it more efficient and ready for the day ahead. So, does research support this? Winston looked at the size of dolphins' cortexes and found that they have unusually large cortexes for mammals of their size. The suggestion that dolphins have more capacity for information would explain why they do not dream. In contrast, the human cortex is smaller and would need to process useless information. However, this is only a theoretical explanation for dreams, as other psychologists believe that the human cortex is folded and therefore potentially much larger than we previously thought. Memory tests conducted by Bahrick has also indicated that the human memory is potentially unlimited in capacity, which raises the question: why do we need to process unwanted information?