Hyperthymesia, also known as hyperthymestic syndrome or highly superior autobiographical memory (HSAM), is a condition that leads people to be able to remember an abnormally large number of their life experiences in vivid detail. It is extraordinarily rare, with fewer than 100 people in the world having been diagnosed with the condition as of 2021[update].[3][4] A person who has hyperthymesia is called a hyperthymesiac.[5]
American neurobiologists Elizabeth Parker, Larry Cahill, and James McGaugh (2006) identified two defining characteristics of hyperthymesia: spending an excessive amount of time thinking about one's past, and displaying an extraordinary ability to recall specific events from one's past.[1] The authors wrote that they derived the word from Ancient Greek: hyper- 'excessive' and allegedly thymesis 'remembering', although such a word is not attested in Ancient Greek, but they may think of Modern Greek thymisi 'memory' or Ancient Greek enthymesis 'consideration', which are derived from thymos 'mind'.[6]