Hyperthymesia is a condition which leads people to be able to remember an abnormally large number of their life experiences in vivid detail.

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. The word "hyperthymesia" derives from Ancient Greek: hyper- ("excessive") and thymesis ("remembering").

Individuals with hyperthymesia can recall much of their lives in near perfect detail, as well as public events that hold some personal significance to them. Those affected describe their memories as uncontrollable associations; when they encounter a date, they "see" a vivid depiction of that day in their heads. Recollection occurs without hesitation or conscious effort.

It is important to draw a distinction between those with hyperthymesia and those with other forms of exceptional memory, who generally use mnemonic or similar rehearsal strategies to memorize long strings of subjective information. Memories recalled by hyperthymestic individuals tend to be personal, autobiographical accounts of both significant and mundane events in their lives. This extensive and highly unusual memory does not derive from the use of mnemonic strategies; it is encoded involuntarily and retrieved automatically.[4] Despite perhaps being able to remember the day of the week on which a particular date fell, hyperthymestics are not calendrical calculators, like some people with savant syndrome. Rather, hyperthymestic recall tends to be constrained to a person's lifetime and is believed to be a subconscious process.

The Downside of Having an Almost Perfect Memory

...DeGrandis says he’s struggled from depression and anxiety, which he believes may be linked to his inability to let certain things go. In getting to know other HSAM study participants, he’s learned this is a common theme.

“I consider myself lucky in that I’ve had a pretty good life, so I have a lot of happy, warm and fuzzy memories I can think back on,” he says. “But I do tend to dwell on things longer than the average person, and when something painful does happen, like a break-up or the loss of a family member, I don’t forget those feelings.”

Research also suggests that people with HSAM tend to have obsessive traits. “Some subjects, like Price, focused on orderliness,” McGaugh wrote in Learning and Memory: A Comprehensive Reference, which was updated this year to include a chapter on HSAM. “Some were germ-avoidant, and some had hobbies that involved intense, focused and sustained efforts,” he added. It’s not known yet whether these traits are the result of their superior memory, or if both are caused by another underlying factor.

And while people with superior memories have an uncanny talent for linking dates and events, they do occasionally make mistakes. “Their memories are much more detailed than ours, and last for a longer period of time, but they’re still not video recordings,” says McGaugh. “Memory is a distracting process, and what we pull from our brains isn’t always entirely accurate.”

People with HSAM are also no better than normal when it comes to remembering things like faces or phone numbers. The ability is not the same as a so-called photographic memory, which allows people to vividly recall details from a scene they’ve only observed for a short time; nor is it the same as a talent held by competitive “memory athletes” who use mnemonic devices to remember long strings of data, for example.

“I’m not great with names, or with mundane details like whether I brushed my teeth today or where I put my keys,” says DeGrandis. “My mind is always moving and filled with so many other things, and maybe that contributes, ironically, to a poorer short-term memory.”