Subject MM Had a Stupendous Memory for Facts, But a Normal Brain

People with what is called Highly Superior Autobiographical Memory (HSAM) have the very rare ability to recall with astonishing detail things that happened almost every day throughout their adult lives -- an ability seemingly many times greater than that of the average person.  Some have suggested that HSAM cases can be explained as being merely the result of superior mnemonic techniques. Others have suggested that press reports about this topic are just exaggeration or sensationalism. But a scientific paper (discussed in my post here) documents the dramatic reality of  Highly Superior Autobiographical Memory (HSAM). The paper documents that certain people have memory about past events that is literally dozens of times better than the average person has. 

Read my post here for a discussion of two studies that attempted to show differences in the brains of those with Highly Superior Autobiographical Memory, but actually failed to show any major differences. The same post has a very interesting discussion of numerous memory marvels with recollection abilities as impressive as those with Highly Superior Autobiographical Memory (HSAM). The 2024 paper here says, "Structural neuroanatomical differences do not appear to characterise HSAM."

In the paper "Remarkable Cases of Memory" by W.D. Henkle in The Journal of Speculative Philosophy, Vol. 5, No. 1 (January, 1871), we read many accounts of people with memories far greater than that of the average man. Here is one account:

"Casaubon thus speaks of Joseph Scaliger: 'There was no subject in which any one could desire instruction which he was not capable of giving. He had read nothing (and what had he not read?) which he did not forthwith remember; there was nothing so obscure or obsolete in any ancient author, Greek, Latin, or Hebrew, with regard to which, when interrogated, he could not at once give a reply. He was at home in the history of all nations and all ages, the successions of government, the affairs of the ancient church; the properties, differences, and names, whether ancient or modern, of animals, plants, metals, and all natural objects, he knew accurately. With the situations of places, the boundaries of provinces, and their division at different times, he was perfectly familiar. He had left untouched none of the severer studies or sciences. So extensive and accurate was his acquaintance with languages, that if, during his lifetime, he had made but this single acquirement, it would have appeared miraculous. He committed [to memory] Homer in twenty-one days, the other Greek writers inside of two years. Sir Wm. Hamilton says, 'taking him all in all, he was the most learned man the world has ever seen. ' "

Later in the same article Henkle states this:

"Seneca, the rhetorician, says that he could repeat in order two thousand names read to him, and that he repeated in reverse order two hundred unconnected verses that had been pronounced by the pupils of his preceptor. Muretus says that he discredited this story until he tested Molino, a young Corsican, residing at Padua as a student of civil law. In the presence of a considerable number of distinguished persons in a saloon, Muretus began to dictate words, Latin, Greek, barbarous, significant and non-significant, disjoined and connected, until he wearied himself, the young man who wrote them down, and the whole company, all becoming marvellously tired, Molino alone alert and fresh wanted more words. Muretus said that he would be satisfied if he repeated half of what had been taken down. Molino, after a brief pause, repeated the words in exact order and without the slightest hesitation, and then repeated them backwards. Next he gave the first, third, fifth, and so on. He repeated them exactly in any order asked. He declared that he could repeat in this way 36,000 words, and remember them a year. ...Dr. Leyden could repeat a long act of parliament, or any similar document, after having once read it; but he could not recollect a particular point without repeating the whole. "

The highlight of the paper is Henkle's discussion of the case of Daniel McCartney, a most astonishing triple-savant with the ability to recall events from his life on any random day, along with the day of the week and weather on any such date, along with a super-human seeming math calculation ability. Henkle documented the case very well by making transcripts of three interviews he had with McCartney. The case is summarized in my previous post here. 

The 2018 paper "Neuropsychological Investigation of 'The Amazing Memory Man' ” documents the case of a subject MM, a 63-year-old man with astonishing abilities of factual recall but only average intellect. We read this about the subject:

"He has a phenomenal memory for events and dates from his personal past, but only average performance on clinical tests and laboratory tasks of new learning capacity. He does not try to memorize material or employ specific mnemonic strategies. These features make MM and other HSAM subjects different from contestants in national and international memory competitions (Maguire et al., 2003; “U.S.A. Memory Championship,” 2016; “World Memory Championship,” 2016)....MM differs from other HSAM subjects in that his extraordinary memory applies to historical events that he did not personally experience (including those long before his birth) and to general world knowledge. Most HSAM subjects have little interest in thinking about events from dates before they were born (McGaugh & LePort, 2014). Thus, the range of material for which MM has exceptional memory appears to be much broader than that of HSAM subjects previously described (see Table 3). "

According to Table 2 of the paper, his autobiographical memory was very good, with him scoring 100% on most aspects of a test. We read the following:

• Recalling previous addresses lived during his lifetime, subject MM could "confidently recall the address of all of his 15 homes, occasionally forgetting only zip codes."
• "He [was] able to recall all 44 presidents, in reverse order and without error, but he often sprinkled his reporting with amusing esoterica about them." The average college student will recall only about 19 of them. 
• "MM was given 30 random dates (e.g., February 20, November 12), and asked to describe the importance of that date in history. Well-known holidays and other dates of historic significance (e.g., July 4, September 11) were avoided. An informal survey of our colleagues produced zero correct responses. MM was successful for 27 of the 30 dates. He often produced more than one correct historical fact for each date, and he occasionally supplemented these with personal memories." 
• " Asked to provide one-word answers to 75 world knowledge questions," MM got 63% correct.  As shown in Figure 3, his performance was about twice as good as college students on the easy questions, ten times as good as the college students on the medium-hard questions, and 25 times as good as the college students on the hard questions. 
• "MM was asked to match the title of each year’s Academy Award-winning Best Picture with the year that it won the award," and answered perfectly for every year between the early 1940's and the early 1990's. 

Subject MM said that his parents had normal memory powers, which argues against any idea that memory abilities such as his have a genetic or neural basis. The authors had the subject undergo 2 MRI brain scans. The authors failed to find anything that might constitute a brain explanation of why MM had such superior memory. A few differences from average are reported here and there, but you will get a few differences from average here and there when you scan the brain of a randomly chosen person and compare it to each of a hundred structural averages in human brains.  We read this:

" Standard clinical evaluation of MM’s brain MRI images revealed no structural abnormalities. In addition, MM’s total brain and hippocampal subregion volumes were unremarkable. This is consistent with most of the previous literature. Although Maguire and colleagues (Chadwick, Bonnici, & Maguire, 2014) found that volume of hippocampal subregion CA3 was associated with degree of confusion about past memories in normal subjects, they also found that winners of international memory competitions had undistinguished brains on structural MRI scans (Maguire et al., 2003)." 

A report such as this is quite consistent with my claim that the brain is not any storage place of human memories, and that memory is not a brain activity.