A general flaw in the human memory system is that there is no built-in way to distinguish definitively between what actually happened and what was only imagined. Thoughts and feelings about what happened often have the same status as do memory traces of what really happened. Social reality is ambiguous. Thus, all that is needed for an unconsciously learned bias to grow stronger is an ambiguous reality, which the bias interprets for you. It is the root of prejudice: you become increasingly convinced of your bias in the the absence of the chance to confirm beliefs.
The "cognitive" unconscious facilitates the non-emotional, mechanical parts of perception and activity that, for example, allow people to speak a sentence in keeping with syntactic rules they cannot explain, or move a hand with precision. Long thought to be simple-minded, new research shows that the cognitive unconscious is extremely smart and in psychological tests was able to master visual display rules which no person could do consciously. The "emotional" unconscious acts by adding emotional content, which can warp the way people perceive and react, as in stage fright.
Psychologists have shown that even an encounter people are not consciously aware of can have a palpable influence on feelings, thoughts and actions. Students learned to infer fairness in strangers (arbitrarily based on facial proportions) after exposure to photographs of slightly lengthened or shortened faces of professors they had previously assessed as fair and unfair. The initial bias can silently confirm itself without actually testing that conclusion against reality.
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