Psychiatric Bulletin (1990), 14,475-476

The savant syndrome

Genius and mental handicap combined

J. A. M. SCHIPPERHEIJN, Locum Senior Registrar in , Napsbury Hospital, Herts; and F. J. DUNNE, Consultant Psychiatrist, Warley Hospital, Brentwood, Essex CM14 5HQ

Idiot-savants are people oflow intelligence who have music and . Calculators are capable of one or two outstanding talents such as calendar cal• remarkable feats ofmental arithmetic, including the culation, drawing, or musical performance. The syn• multiplication of three-figure numbers in a few drome occurs with high frequency among autistic seconds, the rapid calculation of square roots, and children ( is about four times commoner in the description of a geometric series to 64 places boys), and the male to female ratio is about 6: I (Hermelin & O'Connor, 1983). They follow simple suggesting a sex linked disorder (Hill, 1977). It is rules which are used as an aid to recalling dates and estimated to occur in 0.060/0 of the mentally handi• sequences in classical music; the skills though im• capped population or about I in 2,000 ofthose living pressive may be confined to tonal music. Rule-based in institutions (Treffert, 1988). The gift starts appar• strategies are used by all savants and seem to be IQ ently spontaneously between age 5 and 8 years. Fre• independent. quently the parents claim that they themselves do not The phenomenal ability of identical, mentally have the talent and know ofno one in the family who handicapped twins to name the day ofthe week for a has, but there is a tendency for savant skills to run in given date in any year has been explained by the ca• families, suggesting that genetic factors playa role. pacity to subtract multiples of a 4OO-year calendar The syndrome was first described by Langdon cycle from any given year (Horwitz et ai, 1969). Both Down in 1887 but Tredgold (1914) wrote the first twins had a very low level ofconcentration except for definitive account ofthe condition. Several types are questions concerning the calendar. The twins began found: calendar calculators, artists, musicians and by memorising a conventional calendar, then noted . The condition can be congenital, or that one month began where the last left off, and acquired in an otherwise normal individual following subsequently tacked months together, then years, injury to or disease ofthe central nervous system. and so forth. As the 4OO-year cycle is constant, they The skills can appear suddenly and likewise dis• could connect any day and date by subtracting multi• appear without explanation. Regardless of their ples of 400, and were aware of the sub-patterns particular ability, savants all have in common a within the cycle. These feats of memory may not be phenomenal memory. The term itself is a misnomer so astonishing given that the twins devoted their time being derived from the obsolete definition 'idiot' to practically nothing else from the age of nine on• denoting an individual with an IQ of25 or below, and wards; thus, rote memory may be involved. The sav• the word 'savant' or knowledgeable person from the ant's skill may represent a failure to forget rather French 'savoir' meaning, 'to know'. Most savants than an enhanced ability to store ; what have a very low IQ, otherwise they would not be stands out is the capacity for long-term memory. classified as such. Communication problems are Intense practice and appropriate reinforcement common and include low-level grammatical grasp, have been suggested as alternatives to rote memory. slowness, mutism, complete absence of speech, However, it is unlikely that practice alone can ac• hesitant speech, withdrawal and autism (O'Connor, count for the capacity of idiots-savants to compre• 1989). hend the complexities ofmusic, art or mathematics. Calendar calculators and savants with mathemat• Sensory deprivation and social isolation may also be ical ability and exceptional mnemonic skills are the involved: both lead to boredom and to the develop• most frequent; musicians are rare. In some individ• ment ofbizarre or trivial preoccupations and rituals uals, skills are remarkable because of the associated such as memorising obscure facts andcalendarcalcu• mental handicap (talented savants); in others (pro• lating, in a desperate search for stimulation. Some digious savants) the abilities would be considered normal individuals in extreme isolation develop feats spectacular even if they occurred in normal people. of mental calculation or rote memory as a way of Skills can also occur in combination, for instance, adapting; the savant may do the same, but most

475 476 Schipperheijn andDunne people with sensory impairment such as the blind To date, no single theory can explain the savant and the deaf do not develop savant skills. Eidetic syndrome but future research using positron emis• imagery, an intense coloured visual image which is sion tomography (PET) scans, nuclear magnetic aroused and maintained by scanning an object and resonance, cerebral blood flow studies and other persists for at least 40 seconds, may be found in brain mapping techniques may help to provide an the savant calculator but it cannot account for cases anatomical explanation for this extraordinary in which calculations extend into the future, for condition. which no calendars are available (Giray & Barclay, 1977). References The left cerebral hemisphere normally develops BlUNK, T. L. (1980) Idiot savant with unusual mechanical is subject to prenatal later than the right and ability: an organic explanation. American Journal of influences for a longer period oftime. A male factor, Psychiatry, 137,250-251. perhaps testosterone, might slow growth and impair GIRAY, E. F. & BARCLAY, A. G. (1977) Eidetic imagery: neuronal migration in the left brain, with subsequent longitudinal results in brain-damaged children. American enlargement and shift of dominance to the right Journal ofMental Deficiency, 82, 311-314. brain, thus favouring talents associated with right HERMELIN, B. & O'CONNOR, N. (1983) The idiot savant: brain functions (Brink, 1980). Damage to the left flawed genius orclever Hans? Psychological Medicine, 13, hippocampus and amygdala might also be important 47~81. since both are involved in the regulation ofmemory HILL, A. L. (1977) Idiots-savants: rate ofincidence. Percep• tual Motor Skills, 44, 161-162. functions: the hippocampus is responsible for simple HORWITZ, W. A., DEMING, W. E. & WINTER, R. F. (1969) A recall and the amygdala for cataloguing and provid• further account of the idiots savants, experts with the ing emotional tone to memory. Overcompensation calendar. American Journal ofPsychiatry, 126,412-415. by the right hippocampus, for example, could ac• O'CoNNOR, N. (1989) The performance ofthe 'idiot savant': count for the phenomenal memory displayed by implicit and explicit. British Journal of Disorders of savants (Treffert, 1988). Ischaemic or hypoxic injury Communication, 24, 1-20. to the brain either during pregnancy or at birth TREDGOLD, A. F. (1914) Mental Deficiency. New York: have also been proposed as causes ofthe syndrome. Wood. Of particular interest is the triad of blindness, TREFFERT, D. A. (1988) The idiot savant: a review of the syndrome. American JournalofPsychiatry, 14S, 563-572. musical genius and retardation associated with retrolental fibroplasia, suggesting that high oxygen A full list of references is available on request from the concentrations might be responsible. authors.