Most of us are familiar with the 1988 movie Rain Man, which portrays a fictional autistic savant. An autistic savant is an autistic person with serious handicaps which nonetheless coexist with extraordinary talents that seem almost superhuman. Fantastical though a story Rain Man sounds, it is based on a true story. The movie is based on a real person named Kim Peek. Kim Peek
memorized over 6000 books and has encyclopedic knowledge of geography, music, literature, history, sports and nine other areas of expertise (Peek & Hanson 2008). He can name all the US area codes and major city zip codes. He has also memorized the maps in the front of telephone books and can tell you precisely how to get from one US city to another, and then how to get around in that city street by street. He also has calendar-calculating abilities and, more recently, rather advanced musical talent has surfaced. Of unique interest is his ability to read extremely rapidly, simultaneously scanning one page with the left eye and the other page with the right eye. Magnetic resonance imaging (MRI) shows the absence of the corpus callosum along with other substantial central nervous system (CNS) damage (Treffert, 2009).
Treffert notes that mental handicap, blindness and musical genius have all frequently occurred with one another. Women are relatively underrepresented among autistic savants; there is 1 female autistic savant for every 6 male autistic savants, with a ratio of autism in general of 1 female autist for every 4 male autists.
Savant syndrome was first noted in 1783, in an article published in Gnothi Sauton, the German psychology journal. The article described the case of Jedediah Buxton. He was severely mentally disabled but had remarkable calculating ability. The first formal presentation of the syndrome, however, occurred in 1887 by Dr. J Landon Down, of Down Syndrome fame. He referred to them as “idiot savants” and discussed 10 cases of such people. He described one of these savants as capable of reciting The Rise and Fall of the Roman Empire verbatim and could easily recite the entire work.He likewise spoke of other patients who exhibited “music ability, arithmetical genius or precise timekeeping skill, all of which, taken together, compromised a clinical picture of savant syndrome – special skills+phenomenal memory – which unfailingly reoccurs in case reports to this day”(Treffert, 2009).
While the term “idiot” was used of a person with an IQ below 25, most savants possess an IQ of at least 40 (Treffert, 2009). The term “savant” comes from the French “savoir,” for “to know.” Treffert notes that “savant syndrome” is a more accurate term than the popular “autistic savant,” since many savants are not autistic at all, but suffer some other developmental disorder or form of organic brain damage. Of 51 savants, for example, Treffert notes that one researcher found that 41 were autistic (12 of these were ‘prodigious’ savants possessing extraordinary abilities far beyond what is typically observed in any ordinary human). Treffert lists some important works on the subject: Tregedold’s 1914 work includes an important chapter on the subject in “Mental Deficiency,” Hill (1978) published a comprehensive review of literature on the subject from 1890 to 1978, Rimland provided a comprehenesive summary of the subject from 531 cases, selected from a survey consisting of 5,400 autistic children, and Heaton & Wallace furnishes us with a highly comprehensive bibliography on the subejct (Treffert, 2009). Treffert also lists his own 1988 work, “Extraordinary People” and Hermelin’s 2011 work summarizing the doctor’s findings after 20 years of research on savant syndrome.
Dr. Down was famous for his description of the eponymous Down Syndrome, developing developmental disorders into congenital and accidenteal categories (Treffert, 2009). Treffert suspects that Dr. Down anticipated certain insights into autism when he described children who exhibited normal intellectual development at first but then abruptly began to regress. He described a class of developmentally disordered persons who exhibited rhythmic movement patterns, language deficits and relative seclusion. Treffert notes the approprirateness with which Dr. Down described this syndrome as “developmental retardation,” since autism was later class under “developmental disorders” under DSM-III.
Of the 5,400 children surveyed in Rimland’s aforementioned study on autism, 531 were reported as having special abilities. This 10 percent occurrence, Treffert notes, “has become the generally accepted figure in autistic disorder”(Treffert, 2009). Treffert notes that the incidence of savant syndrome among the developmentally disabled is around 1 in 2,000, though some estimate 1.4 in 1,000. Treffert summarizes:
Whatever the exact figures, mental retardation and other forms of developmental disability are more common than autistic disorder, so a reasonable estimate might be that approximately 50 per cent of persons with savant syndrome have autistic disorder and the other 50 per cent have other forms of developmental disability, mental retardation or other CNS injury or disease. Thus, not all autistic persons have savant syndrome and not all persons with savant syndrome have autistic disorder (Treffert, 2009)
But why does savant syndrome can to occur so disproportionately among men? Geschwind & Galaburda suggest that prenatal exposure of testosterone to the male brain damages and/or slows neuronal growth in the left hemisphere, with the right-hemisphere increasing in size to compensate for the damage (Treffert, 2009).
This finding may account as well for the high male : female ratio in other disorders, including autism itself since left hemisphere dysfunction is often seen in autism (Treffert 2005, 2006a). Other conditions, such as dyslexia, delayed speech and stuttering, also have a male predominance in incidence, which may be a manifestation of the same left hemisphere growth interference in the prenatal period described above (Treffert, 2009).
Although always extraordinary and intriguing, the skillset of such savants is oftentimes quite unusual and highly specialized:
Considering all the abilities in the human repertoire, it is interesting that savant skills generally narrow to five general categories: music, usually performance, most often piano, with perfect pitch, although composing in the absence of performing has been reported as has been playing multiple instruments (as many as 22); art, usually drawing, painting or sculpting; calendar calculating (curiously an obscure skill in most persons); mathematics, including lightning calculating or the ability to compute prime numbers, for example, in the absence of other simple arithmetic abilities; and mechanical or spatial skills, including the capacity to measure distances precisely without benefit of instruments, the ability to construct complex models or structures with painstaking accuracy or the mastery of map making and direction finding.
Other skills have been reported less often, including: prodigious language (poly-glot) facility; unusual sensory discrimination in smell, touch or vision including synaesthesia; perfect appreciation of passing time without benefit of a clock; and outstanding knowledge in specific fields such as neurophysiology, statistics or navigation. In Rimland’s (1978) sample of 543 children with special skills, musical ability was the most frequently reported skill followed by memory, art, pseudo-verbal abilities, mathematics, maps and directions, coordination, calendar calculating and extrasensory perception. Hyperlexia, which is distinguished by precocity rather than age-independent level of skill, has also been frequently reported in autism (Grigorenko et al. 2002) (Treffert, 2009)
Phenomenal memory is an essential feature of savant syndrome, and although savants usually possess only one specific set of skills, they sometimes possess numerous skills, especially in autistic savants. A subclass of savants are known as “prodigious” savants. In these cases, their skills are so extraordinary that they are virtually unheard of in normal persons. Treffert notes the various terms used of this remarkable memory, citing Down (1887), who referred to it as ‘verbal adhesion,’ Critchley (1979), who referred to it as ‘exultation of memory’, Tredgold (1914), who referred to it as ‘automatic’, and Barr (1898) who referred to it as ‘an exaggerated form of habit'(Treffert, 2009). He notes that many researchers of this syndrome see it as a kind of
“non-conscious ‘habit formation rather than a ‘semantic’ memory system. They proposed two different neural circuits for these two different types of memory: a higher level corticolimbic circuitu for semantic memory and a lower level cortico-striatal circuit for the more primitive habit memory, which is sometimes referred to as procedural or implicit memory. Savant memory is characteristically very deep, but exceedingly narrow, within the confines of the accompanying special skill”(Treffert, 2009)
While savant syndrome ordinarily occurs in childhood, accompanying a developmental disorder, they can also appear in adults following some form of brain damage. He also notes reports of fronto-temporal dementia patients who acquire intriguing skills following the progression of the disease, and in spite of its otherwise devastating effects.
While their extraordinary but relatively ‘mechanical’ reproduction of patterns (as in savants who exhibit musical genius) is sometimes associated with lack of creativity, Treffert notes that this is not quite accurate. In the case of Leslie Lemke, Treffert notes that he reproduced Tchaikovsky’s first piano concerto perfectly without having ever heard it before, eventually becoming bored with the song and began to create new songs. He also notes a well-known Japanese savant who has produced 40 original songs.
But where does savant syndrome come from? How and why does it develop? Scientists are not sure. Treffert believes that in at least some cases, it stems from “left brain dysfunction with right brain compensation”(Treffert, 2009).
Treffert, Darold. The savant syndrome: an extraordinary condition. A synopsis: past, present, future. Philos Trans R Soc Lond B Biol Sci. May 27, 2009; 364(1522): 1351–1357.
doi: 10.1098/rstb.2008.0326. Retrieved from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2677584/