What is hyperthymesia

Hyperthymesia also known as “highly superior autobiographical memory” or “perfect autobiographical memory” ¹. Hyperthymesia (Highly Superior Autobiographical Memory) participants have a remarkable ability to recall details of personal and public events over an extensive range of lifetime periods ². This ability suggests that they may be unable to forget and, thus, are able to preserve a remarkable richness of detail concerning autobiographical events. Normally, the passage of time is known to have two hallmark effects on event memory. First, forgetting of information tends to occur at a roughly exponential rate ³. Second, the quality of a memory, even the most memorable, generally becomes altered as time passes ⁴. While individuals with hyperthymesia have detailed memory for previous autobiographical events, the rate of forgetting and the quality and quantity of these memories has not been previously investigated in sufficient detail. Hyperthymesia individuals can remember the day of the week a date fell on and details of what happened that day from every day of their life since mid-childhood. For details that can be verified, hyperthymesia individuals are correct 97% of the time ⁵. For example, when one individual was asked what happened on October 19, 1987, she immediately responded with, “It was a Monday. That was the day of the big stock market crash and the cellist Jacqueline du Pré died that day.” Hyperthymesia individuals can remember what happened on a day a decade ago better than most people can remember a day a month ago. In some ways, these abilities seem to be at odds with what scientists know about the reconstructive, unreliable, and malleable processes underlying memory in people with typical memory ¹.

Individuals who have Highly Superior Autobiographical Memory (hyperthymesia) demonstrate the ability to recall accurately vast amounts of remote salient autobiographical events without the explicit use of mnemonics ². Hyperthymesia individuals forget autobiographical details at a far slower rate than do age- and sex-matched controls ⁶. Furthermore, in comparison with controls, hyperthymesia participants maintain more richly detailed recollections and their forgetting curve for autobiographical memory is shallow, which should come as no surprise given the nature of their memory ². The data here suggest that hyperthymesias are not better than controls in acquiring information. However, they are far superior at retaining information.

Hyperthymesia abilities are distinct from previously described superior-memory individuals (mnemonists) ⁷ who typically rely upon practiced mnemonics to remember unusually long lists of domain-specific data, yet remain average in their ability to retrieve autobiographical information. One technique used by mnemonists for producing strong memories is through overt intensive memorization of material and or use of mnemonic techniques ⁸. In contrast, hyperthymesia individuals report that they do not rehearse their experiences or use mnemonic techniques with the explicit intent to create strong memories, unlike many memory experts ⁹. Interestingly, although hyperthymesic individuals have exceptional autobiographical memory, they are no better than control subjects at laboratory memorization tasks ². Therefore, the study of individuals who have strong and lasting memories of ordinary daily experiences provides a novel perspective from which to investigate memory encoding, storage, and retrieval.

Hyperthymesia individuals seem not to be superior learners, exhibiting average scores on typical laboratory memory tasks that are unrelated to autobiographical memory. Furthermore, hyperthymesia individuals recall their past in rich detail and in a fashion that seems automatic and unaided by explicit mnemonic techniques or rote practice. It is puzzling that not all hyperthymesia individuals report keeping diaries, routinely refreshing information (e.g., “what did I do on this day last year?”), or categorizing and cataloging their experiences on certain dates in their minds. The sheer amount of the personal experiences that they can recall fluidly seems highly unusual, and on objective measures of autobiographical memory the statistics are astounding. For example, on the very challenging 10 Date Quiz, the mean score for hyperthymesia participants is 25.5 standard deviations above the mean score for control participants. Structural MRI brain scans of people with hyperthymesia have shown morphological differences in areas, such as the temporal gyri, that have been previously described as contributing to autobiographical memory ¹⁰. These areas were different in size and shape compared with age- and sex-matched controls, but conclusions have yet to be made as to if these differences are a result of nature, nurture, or both.

LePort et al. ⁶ suggested the possibility that hyperthymesia participants may be incidentally strengthening their memories. LePort et al. ⁶ also suggested that hyperthymesia may be a unique form of obsessive compulsive disorder (OCD). Not only do hyperthymesia participants express obsessive tendencies, but also the authors have found previously similarities between the structure of their brain and that of OCD patients. Namely, both populations share an enlarged caudate and putamen ². It is worth noting that many OCD patients actually demonstrate impairments in autobiographical memory, which may be a result of co-morbid diagnosis of depression ¹¹. In contrast, hyperthymesia participants, by means of an obsessive habit, may acquire and habitually use an implicit ability to embed autobiographical information within a larger memory network.

Subsequent research clarifying neurobiological similarities and differences between an OCD patient population and hyperthymesia participants would provide further insight into mechanisms of hyperthymesia more greatly related to OCD or autobiographical memory. Namely, similarities in the functional connectivity of the orbitofronto-striatal circuitry would signify a pathophysiology comparable to that of OCD patients ¹². Differences in the functional connectivity of the Default Mode Network, previously shown to be important for self-referential thought, self-projection and autobiographical remembering (Buckner et al., 2008), would point to neurobiological processes possibly contributing to hyperthymesia, but distinct from OCD. Future research will be needed to directly compare the neural and behavioral profiles of hyperthymesia and OCD to further investigate this relationship.

Hyperthymesia symptoms

Hyperthymesia is not an illness. Hyperthymesia or Highly Superior Autobiographical Memory, simply means people with hyperthymesia have a remarkable ability to recall details of personal and public events over an extensive range of lifetime periods ². This ability suggests that they may be unable to forget and, thus, are able to preserve a remarkable richness of detail concerning autobiographical events.

Hyperthymesia causes

The cause of hyperthymesia is currently unknown and is an area of ongoing active research.

Hyperthymesia test

Currently the diagnosis of hyperthymesia involves complex screening and cognitive tests done in few research laboratories ¹³.

Hyperthymesia screening procedures

The Public Events Quiz consisted of thirty questions presented over the telephone ¹³. It contained two types of questions: fifteen asked for the date of a given significant public event that took place within the individuals’ lifetime (e.g., When did Jimmy Carter win the Nobel Peace prize?); fifteen asked for the significant public event that took place on a given date that fell within the individual’s lifetime. In addition, for all 30 questions, individuals were asked to state the day of the week the date fell on. The order of presentation of the two types of questions was interchanged. The significant public events given were selected from five different categories: Sporting events, political events, notable negative events, events concerning famous people and holidays. The participant received one point for each correctly identified category (i.e., the event, the day of the week, the month, the date and the year) and could achieve a total of 88 possible points. Percentages scored were calculated for each individual claiming to have hyperthymesia as well as each screening control. A score of 50% or above qualified an individual claiming to have hyperthymesia to advance to the second even more challenging round of screening, the 10 Dates Quiz.

The 10 Dates Quiz consisted of ten computer generated random dates, ranging from the individuals’ age of fifteen to the day of testing. It was administered via the telephone with no time limits. Individuals were asked to provide three different categories of information for each of the 10 dates generated: (1) the day of the week; (2) a description of a verifiable event (i.e. any event that could be confirmed via a search engine) that occurred within ± one month of the generated date; (3) a description of a personal autobiographical event the individual participated in. One point was awarded for the correct day of the week, for giving a verifiable event confirmed as true, and/or for giving a personal autobiographical event. A maximum of three possible points per date could be achieved (thirty points total). The percentage scored for each category as well as the total score, the average of all three categories, was calculated. A total score of 65% or above qualified the individual as an hyperthymesia participant and for further, in person, behavioral and neuroanatomical testing.

Cognitive tests

Following the screening procedure, hyperthymesia participants were brought to the laboratory and examined with a cognitive battery consisting of thirteen behavioral tests assessing autobiographical memory, various types of learning and memory, obsessional tendencies hand dominance and depression levels. The choice of tasks was driven by our prior experience with hyperthymesia individuals and by our desire to assess different aspects of their memory ability. The battery took approximately an hour and a half to complete. Three participants failed to complete the entire battery. The number of participants who took each test is detailed in the results.

Autobiographical Memory Task

Autobiographical memory was assessed following a modified cued-recall procedure based on Pohl, Bender, and Lachmann ¹⁴. Each participant was asked to recall five specific personal events, chosen such that answers could be verified for accuracy. Participants had no prior knowledge of which personal events would be asked. The five specific events were: First day at university; First day of elementary school; 18th birthday celebration; Address and description of the first place they resided after moving out of parents’ house; Last final exam in college.

Participants were asked to recall verbally each event in as much detail as possible and encouraged to include details such as dates, weather, names of others present and location. At the conclusion of the test, participants were asked to supply the following items for verification of the accuracy of their memories: College transcripts, correspondence from first address, kindergarten or 1st grade class photo, pictures from 18th birthday celebration, diaries and calendars.

Two separate scores were devised, one for ‘AMT Verifiable Details Score’ and one for ‘AMT Total Details Score’. Details for the ‘AMT Verifiable Details Score’ were verified via personal documents, calendars, or web searches (using sites such as historical weather databases, Google Maps and news articles) and given one point if accurate. The percentage correct out of all verifiable details was calculated. Details for the ‘AMT Total Details Score’ were not verified. One point was given regardless of whether a detail could or could not (e.g., conversations, thoughts, emotions etc.) be verified by the researcher.

Names to faces

The recall of names paired with faces was assessed following a modified procedure based on Morris, Jones, and Hampson ¹⁵. Participants were shown fourteen unknown faces (seven male, seven female), for two seconds each. Each face was verbally assigned a first and last name. All faces were presented in frontal position with a neutral expression. Immediately following the study phase, the faces were shown in the same order and participants were asked to recall the name previously associated with each face. The facial images were selected from the Wechsler Memory Scale-III (WMS-III) Faces subtest. Names were generated using an online random name generator that uses US census data to randomly generate male and female names (http://random-name-generator.info/http:/www.kleimo.com/random/name.cfm). One point was given for a correctly given first and last name paired with the appropriate face (maximum of 2 points per face).

Visual memory

Visual memory was assessed following a procedure developed by Marks ¹⁶. Participants were shown a stimulus consisting of a set of 15 unrelated objects for 20 seconds. Following the distraction question, “Would you like a drink of water?” they were asked five questions regarding the objects and their locations. If they were unable to answer a question, a prompt directly followed consisting of three options, one of which was the correct answer. A correct answer without a prompt was given two points. A correct answer with a prompt was given one point.

Forward and backward digit span

Auditory short-term recall was assessed following a modified version of the WMS-III digit span. Participants were presented with a series of number sequences that increased in length, incrementally with every correct response. After each individual number sequence, participants were asked to either repeat it verbatim or in reverse order. The test was concluded after two consecutive incorrect responses. One point was given for each correctly repeated sequence.

Visual reproduction

Visual memory was assessed following a modified version of the WMS-III Visual Reproduction Subtest. Participants were given ten seconds to look at an abstract design, and then asked to draw the design from memory on a blank sheet of paper. Scores were assigned according to the WMS-III with a maximum of thirty possible points.

Logical memory test

Memory for story content, presented verbally, was assessed using a modified version of the WMS-III Logical Memory Subtest. Free-recall and recognition tests were administered. Participants were read Story A of the WMS-III Logical Memory by the examiner and immediately after asked to verbally recall the story in as much detail as possible. One point was given for each correctly recalled key word or phrase. Hyperthymesia performance for the free-recall portion was compared with that of MRI Controls. Immediately following the free-recall portion hyperthymesia participants and Cognitive Battery Controls were asked 15 yes or no questions about the story. A point was given for each correct answer.

Verbal paired associates

Verbal memory was assessed following a modified version of the WMS-III. Participants were read a series of eight word pairs at a rate of one word pair per three seconds. Immediately following the eight pair list, they were prompted with the first word of a given pair and instructed to give the correct corresponding word. The order of first words presented during the test phase differed from the order of the original word pairs. One point was given for each correct answer.

Leyton Obsessional Inventory Score-Short Form

Common obsessional symptoms were assessed using the Leyton Obsessional Inventory Score-Short Form (LOI-SF) ¹⁷ as prior encounters with a number of the individuals demonstrated a potential obsessional component. The LOI-SF self-report inventory consists of thirty “Yes/No” questions assessing the presence or absence of obsessional symptoms focusing on concerns of contamination and honesty, the presence of repeating behaviors, uncomfortable thoughts/doubts and checking behaviors, allotting too much attention to detail, strictness with one’s conscience and routine, taking a long time to dress, hang up and put away clothing, and lastly belief in extremely unlucky numbers. Participants could score a maximum of thirty points. Approximately half of the questions were reverse scored to account for simple response biases.

Edinburgh Handedness Inventory

Hand dominance in everyday activities was assessed using the Edinburgh Handedness Inventory (EHI) ¹⁸. Participants were given a copy of the EHI and asked to self-report hand use preferences.

Becks Depression Inventory II

The severity of depression was assessed using the Becks Depression Inventory II (BDI-II). Hyperthymesia participants were given a copy of the BDI-II and asked to complete 21 multiple-choice self-report questions relating to symptoms of depression. Note that hyperthymesia performance was compared with that of MRI Controls.

Hyperthymesia treatment

Hyperthymesia is not an illness as such no treatment is required.

References

1. Patihis L, Frenda SJ, LePort AK, et al. False memories in highly superior autobiographical memory individuals. Proc Natl Acad Sci U S A. 2013;110(52):20947-52. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3876244/
2. LePort A. K. R., Mattfeld A. T., Dickinson-Anson H., Fallon J. H., Stark C. E. L., Kruggel F., et al. (2012). Behavioral and neuroanatomical investigation of highly superior autobiographical memory (HSAM). Neurobiol. Learn. Mem. 98 78–92. 10.1016/j.nlm.2012.05.002
3. Wixted J. T., Carpenter S. K. (2007). The wickelgren power law and the Ebbinghaus savings function. Psychol. Sci. 18 133–134. 10.1111/j.1467-9280.2007.01862.x
4. Levine B., Svoboda E., Hay J. F., Winocur G., Moscovitch M. (2002). Aging and autobiographical memory: dissociating episodic from semantic retrieval. Psychol. Aging 17 677–689. 10.1037/0882-7974.17.4.677
5. LePort AKR, et al. Behavioral and neuroanatomical investigation of Highly Superior Autobiographical Memory (HSAM) Neurobiol Learn Mem. 2012;98(1):78–92
6. LePort AK, Stark SM, McGaugh JL, Stark CE. Highly Superior Autobiographical Memory: Quality and Quantity of Retention Over Time. Front Psychol. 2016;6:2017. Published 2016 Jan 21. doi:10.3389/fpsyg.2015.02017 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4720782/
7. Wilding J, Valentine E. Superior Memory. Hove, East Sussex: Psychology Press; 1997.
8. Foer J. (2011). Moonwalking with Einstein: The Art and Science of Remembering Everything. London: Penguin.
9. Ericsson K. A., Moxley J. H. (2014). “Experts’ superior memory: from accumulation of chunks to building memory skills that mediate improved performance and learning,” in SAGE Handbook of Applied Memory, eds Perfect T. J., Lindsay D. S., editors. (London: Sage Publishing; ), 404–420
10. LePort AKR, et al. Behavioral and neuroanatomical investigation of Highly Superior Autobiographical Memory (HSAM) Neurobiol Learn Mem. 2012;98(1):78–92.
11. Wilhelm S., McNally R. J., Baer L., Florin I. (2011). Autobiographical memory in obsesssive-compulsive disorder. Br. J. Clin. Psychol. 36 21–31. 10.1111/j.2044-8260.1997.tb01227.x
12. Menzies L., Chamberlain S. R., Laird A. R., Thelen S. M., Sahakian B. J., Bullmore E. T. (2008). Integrating evidence from neuroimaging and neuropsychological studies of obsessive-compulsive disorder: the orbitofronto-striatal model revisited. Neurosci. Biobehav. Rev. 32 525–549. 10.1016/j.neubiorev.2007.09.005
13. LePort AK, Mattfeld AT, Dickinson-Anson H, et al. Behavioral and neuroanatomical investigation of Highly Superior Autobiographical Memory (HSAM). Neurobiol Learn Mem. 2012;98(1):78-92. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3764458/
14. Pohl RF, Bender M, Lachmann G. Autobiographical memory and social skills of men and women. Applied Cognitive Psychology. 2005;19:745–759.
15. Morris PE, Jones S, Hampson H. An imagery mnemonic for the learning of people’s names. British Journal of Psychology. 1978;69:335–336
16. Visual imagery differences in the recall of pictures. Marks DF. Br J Psychol. 1973 Feb; 64(1):17-24.
17. The structure of obsessionality among young adults. Mathews CA, Jang KL, Hami S, Stein MB. Depress Anxiety. 2004; 20(2):77-85.
18. The assessment and analysis of handedness: the Edinburgh inventory. Oldfield RC. Neuropsychologia. 1971 Mar; 9(1):97-113.