Hyperthymesia, also known as piking[1] or hyperthymestic syndrome[2] is a condition in which the individual possesses a superior autobiographical memory, meaning they can recall the vast majority of personal experiences and events in their lives. The term “hyperthymesia" is derived from the Greek words thymesis, meaning "remembering" and hyper meaning “excessive”.
As first described in a 2006 Neurocase article by Elizabeth Parker, Larry Cahill, Dr. Paul Tejera, and James McGaugh, the two defining characteristics of hyperthymesia are "1) the person spends an abnormally large amount of time thinking about his or her personal past, and 2) the person has an extraordinary capacity to recall specific events from his or her personal past".[2]
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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.[3] 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 memorise 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 being able to remember the day of the week on which a particular date fell, hyperthymestics are not calendrical calculators like some people with autism or savant syndrome. Rather, hyperthymestic recall tends to be constrained to a person’s lifetime and is believed to be an unconscious process.
Although hyperthymestics are not autistic, and likewise savants do not memorise autobiographical information, there are certain similarities between the two conditions. Like autistic savants, individuals with hyperthymesia have an unusual and obsessive interest in dates. Russian psychologist Aleksandr Luria documented the famous case of mnemonist Solomon Shereshevskii[5], who was quite different from the first documented hyperthymestic known as AJ in that he could memorise virtually unlimited amounts of information deliberately, while AJ could not - she could only remember autobiographical information (and events she had personally seen on the news or read about). In fact, she was not very good at memorising anything at all, according to the study published in ‘’Neurocase’’. Hyperthymestic individuals appear to have poorer than average memory for arbitrary information. Another striking parallel drawn between the two cases was that Shereshevskii exemplified an interesting case of synaesthesia[6] and it has been suggested that superior autobiographical memory is intimately tied to time-space synaesthesia.[7]
Twenty cases of hyperthymesia have been confirmed thus far.[8][9][10], the most famous of these being AJ (who later revealed her identity as Jill Price[11]). Her case was originally reported by researchers from the University of California, Irvine - Elizabeth Parker, Larry Cahill and James McGaugh - and is credited as being the first case of hyperthymesia. AJ can apparently recall every day of her life from when she was 14 years old: "Starting on February 5th, 1980, I remember everything. That was a Tuesday."[12]
As the condition becomes better known, more and more people who claim to have hyperthymestic abilities are coming forward. In the aftermath of the 2006 Neurocase publication alone, more than 200 people contacted McGaugh; however only a handful of cases were determined to be actual cases of hyperthymesia. The second verified case was Brad Williams,[13][14][15], the third was Rick Baron[16], and in 2009 Bob Petrella became the fourth person diagnosed with hyperthymestic syndrome[17] . Unusually, all three of these men are left-handed. On December 19, 2010, actress Marilu Henner was featured on 60 Minutes for her superior autobiographical memory ability. Henner claimed she can remember almost every day of her life since she was 11 years old[18][19]. The show was initially pitched as a story featuring hyperthymestic violinist Louise Owen, but the reporter Lesley Stahl volunteered her friend Marilu Henner as having a similar ability[3].
Parker and colleagues used a variety of standardised neuropsychological tests in their diagnosis of AJ’s hyperthymesia. These included tests of memory, lateralisation, executive functions, language, calculations, IQ, visual-spatial and visual-motor functions[2]. They also devised novel tests to examine the extent of her memory abilities. These mostly consisted of questions pertaining to specific dates and events in history. Some of her personal recollections were verified with diary entries as well as by her mother.[2]
Hyperthymestic abilities can have a detrimental effect on cognitive capacity. The constant, irrepressible stream of memories has caused significant disruption to AJ’s life. She described her recollection as "non-stop, uncontrollable and totally exhausting" and as "a burden".[2] Like all hyperthymestics, AJ is prone to getting lost in remembering. This can make it difficult to attend to the present or future as she is permanently living in the past.
Surprisingly, AJ displays considerable difficulty in memorising allocentric information. "Her autobiographical memory, while incredible, is also selective and even ordinary in some respects," - McGaugh.[2] This was demonstrated by AJ's poor performance on standardised memory tests. At school, AJ was an average student, clearly unable to apply her exceptional memory to her studies. Similar patterns have been observed in other cases of hyperthymesia.
Deficits in executive functioning and anomalous lateralisation were also identified in AJ. These cognitive deficiencies are characteristic of frontostriatal disorders (see Causes| Biological).[2]
Due to the scarcity of hyperthymestic individuals, relatively little is known about the processes governing this superior memory ability.
It has been proposed that the information encoded by hyperthymestics is semantic and therefore semantic cues are used in retrieval. Once cued, the memory is retrieved as episodic and follows a pattern similar to that of a spreading activation model. This is particularly evident AJ’s case. She describes how one memory triggers another, which in turn triggers another and how she is powerless to stop it: "It's like a split screen; I'll be talking to someone and seeing something else.”[2] This theory serves to explain why hyperthymestics have both a sense of ‘knowing’ (semantic memory) and ‘remembering’ (episodic memory) during recollection. Hence, hyperthymesia is essentially superior semantic autobiographical memory.[2]
Individuals with hyperthymesia often display OCD tendencies. AJ reports that from a young age, she would become upset when order in her environment was disturbed. She kept a daily diary for 32 years as a way of maintaining control over her environment. Hoarding behaviour is also common[12], both AJ and Williams collect TV guides. This obsessive-compulsive nature may be facilitating consolidation of memories and could explain the unconscious use of dates as organised mnemonic devices.[20]
The theory that hyperthymestic abilities could be attributed to a failure in our cognitive capacity to forget superfluous information has been suggested by numerous researchers.[4] Parker et al report on how executive difficulties, such as lack of inhibition, may explain the constant and unstoppable memory retrieval. “It is, however, quite possible that there is no causal relationship and that the overall parallels between her memory and her neuropsychological weaknesses are simply correlative.”[2]
An MRI study conducted on AJ provides a solid argument as to the neurological foundation of her superior memory[12] [21]. Both the temporal lobe and the caudate nucleus were found to be enlarged. The hippocampus, located in the medial temporal lobe, is involved in the encoding of declarative memory (memory for facts and events), while the temporal cortex is involved in the storage of such memory.[22] The caudate nucleus is primarily associated with procedural memory, in particular habit formation, and is therefore intrinsically linked to Obsessive Compulsive Disorder. Parker and colleagues speculated that a defective frontostriatal circuit could be responsible for the observed executive function deficits in hyperthymesia. This circuit plays a crucial role in Neurodevelopmental disorders such as ASD, OCD and ADHD. Given the parallels in some aspects of behaviour, it is possible that AJ’s hyperthymestic abilities stem from atypical neurodevelopment.
This evidence provides significant support both for the extraordinary memory abilities and the behaviours of hyperthymestics. Scientists now need to ascertain if and how these brain areas are connected in order to establish a coherent neurological model for superior autobiographical memory. "This may be a key piece of the puzzle as to how memory works”
The debate as to whether hyperthymestic syndrome can be considered a distinct form of memory is ongoing.
K. Anders Ericsson of Florida State University does not believe that there is sufficient evidence to suggest that the skills of AJ and Williams need additional explanation: "Our work has pretty much concluded that differences in memory don't seem to be the result of innate differences, but more the kinds of skills that are developed."[23]
McGaugh rejects the idea that hyperthymestic syndrome can be explained away so easily, he argues that there is no explanation as to how they are able to memorise so much: "You'd have to assume that every day they rehearse it... The probability of these explanations dwindles as you look at the evidence."[23]
Cases of hyperthymesia have forced many people to re-evaluate what is meant by “healthy” memory: “it isn't just about retaining the significant stuff. Far more important is being able to forget the rest.”[23]
There is also significant debate over the limits of our memory capacity. Some are of the view that the brain contains so many potential synaptic connections that, in theory at least, there is no limit to the number of long-term memories that the brain can store. In 1961, Wilder Penfield reported that specific stimulation of the temporal lobes resulted in vivid recollection of memories. He concluded that our brains were making "continuous, effortless, video-like recordings" of our experiences, but that these records are not consciously accessible to us.[24]
The main character, Carrie Wells played by Poppy Montgomery, of the CBS television series Unforgettable, possesses superior memory capabilities which she uses to help solve crimes under investigation by the police. Her abilities are attributed to her having Hyperthymesia.