Hypermnesia is an extreme degree of retentiveness and recall, with unusual clarity of memory images. In forensic contexts, eyewitnesses have demonstrated increased recall after undergoing hypnotic induction to help retrieve memories, but such memories have been ruled inadmissible in some U.S. courts. Hyperthymesia, or the hyperthymestic syndrome, is the ability to remember an abnormally large number of life experiences in vivid detail, and is also known as highly superior autobiographical memory (HSAM).

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