As of 2017, less than 100 people have been diagnosed with Highly Superior Autobiographical Memory. Highly Superior Autobiographical Memory (HSAM) is a memory phenomenon first described by researchers at the Center for the Neurobiology of Learning and Memory at UC Irvine. Individuals with HSAM have a superior ability to recall specific details of autobiographical events, tend to spend a large amount of time thinking about their past and have a detailed understanding of the calendar and its patterns.
On December 19, 2010, actress Marilu Henner was featured on the US television program 60 Minutes for her superior autobiographical memory ability. Henner claimed she could remember almost every day of her life since she was 11 years old. The show was initially pitched as a story featuring hyperthymestic violinist Louise Owen, but the reporter Lesley Stahl volunteered her friend Henner as having a similar ability.
Individuals with hyperthymesia can recall almost every day 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. Despite 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.
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.
Some can also have poorer short term memory.
MRI studies of their brain show preliminary evidence of specific regions and networks that may be different from control participants, although this is work that is still quite preliminary.
They have also identified several children with this ability, and are now conducting genetic studies in twins to understand the potential genetic basis of this ability.