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Posted by Sylvia on Saturday, December 27, 2003 (22:45:44)
written by Dr. Darold A. Treffert
What is savant syndrome?
Savant Syndrome is a rare, but spectacular, condition in which persons with various developmental disorders, including autistic disorder, have astonishing islands of ability, brilliance or talent that stand in stark, markedly incongruous contrast to overall limitations. The condition can be congenital (genetic or inborn), or can be acquired later in childhood, or even in adults.
The savant skills co-exist with, or are superimposed upon, various developmental disabilities including autistic disorder, or other conditions such as mental retardation or brain injury or disease that occurs before (pre-natal) during (peri-natal) or after birth (post-natal), or even later in childhood or adult life. The extraordinary skills are always linked with prodigious memory of a special type — exceedingly deep but very, very narrow.
How common is savant syndrome?
Approximately one in ten (10%) of persons with autistic disorder have some savant skills. In other forms of development disability, mental retardation or brain injury, savant skills occur in less than 1% of such persons (approximately 1:2000 in persons with mental retardation).
Since these other forms of mental disability are much more common than autistic disorder however, it turns out that approximately 50% of persons with savant syndrome have autistic disorder, and the other 50% have some other form of developmental disability, mental retardation or brain injury or disease. Thus not all savants are autistic, and not all autistic persons are savants.
What is the range of savant skills?
Savant skills exist over a spectrum of abilities. The most common savant abilities are called splinter skills. These include behaviors such as obsessive preoccupation with, and memorization of, music and sports trivia, license plate numbers, maps, historical facts, or obscure items such as vacuum cleaner motor sounds, for example. Talented savants are those persons in whom musical, artistic, mathematical or other special skills are more prominent and highly honed, usually within an area of single expertise, and are very conspicuous when viewed against their overall handicap.
The term prodigious savant is reserved for those very rare persons in this already uncommon condition where the special skill or ability is so outstanding that it would be spectacular even if it were to occur in a non-handicapped person. There are probably fewer than 50 prodigious savants living worldwide at the present time who would meet this high threshold of special skill.
What are the typical savant skills?
Particularly striking is the consistent observation also over this past century that savant skills typically, and curiously, are generally confined to only about five general areas of expertise — music, art, lightning calculating or other mathematical skills, calendar calculating and mechanical/spatial skills.
This very limited, but spectacular, array of special skills is noteworthy considering the much wider palette of skills in the human repertoire, and the rarity of the obscure skill of calendar calculating in the general population, which seems an ability almost universal, innately so, among savants.
Music is the generally the most common savant skill-usually playing piano by ear and almost always with perfect pitch. Other percussion instruments such as marimba or drums can be mastered as well, but much less frequently. Musical performance abilities predominate, but outstanding composing skills have been documented as well, most often linked to performance ability, but not necessarily so. The triad of mental disability, blindness and musical genius occurs with a curious, conspicuous frequency in reports over this past century, particularly when one considers the relative rarity of each of those circumstances individually.
Artistic talent, usually painting or drawing, is seen next most frequently. Other forms of artistic talent can occur as well, such as sculpting. Lightning calculating or other mathematical skills, such as the ability to compute multi-digit prime numbers contrasted with the inability to perform even simple arithmetic, has often been reported. Mechanical ability, constructing or repairing intricate machines or motors for example, or spatial skills such as intricate map and route memorizing, or being able to compute distances with precise accuracy just from visualization, do occur, but are seen somewhat less frequently.
Calendar calculating is curiously and conspicuously common among savants, particularly considering the rarity of that obscure skill in the general population. Beyond being able to name the day of the week that a date will occur on in any particular year, calendar calculating includes being able to name all the years in the next 100 in which Easter will fall on March 23rd, for example, or all the years in the next 20 when July 4 will fall on a Tuesday. The so-called 'calculating twins' reported extensively in the literature, have a calendar calculating span of over 40000 years backward or forward in time. They also remember the weather for every day of their adult life.
Other skills are occasionally seen including multilingual acquisition ability or other unusual language (polyglot) skills, exquisite sensory discrimination in smell or touch, perfect appreciation of passing time without access to a clock face, or outstanding knowledge in specific fields such as neurophysiology, statistics, history or navigation, to name a few. While always controversial, there have been some reports of extra-sensory perception skills occurring in savants as well.
Typically a particular one of these skills occurs singly in each person with savant syndrome. However in some instances multiple skills occur in the same person. Regardless of the type of skill, it is always combined with prodigious memory, and it is this special kind of memory-extraordinarily deep but very, very narrow — that cuts across all the various special skills and welds the condition of savant syndrome together.
Why is savant syndrome seen more frequently in males than females?
Savant syndrome does occur four to six times more frequently in males than females. Partly that is due to the fact that savant syndrome occurs in as high as 10% of persons with autistic disorder where that same disproportionate male:female ratio is seen. Even beyond that, however, research by Geschwind and Galaburda, explained in greater detail elsewhere on this site, demonstrated in the developing human fetus the left hemisphere of the brain always completes its development later than the right hemisphere. Therefore the left hemisphere of the brain is exposed for a longer period of time than the right to brain insult or injury of any kind.
One such type of neuronal damage can be produced by circulating testosterone, which in the male fetus, reaches very high levels and can be, in some instances, neurotoxic. This same testosterone mediated developmental injury, causing left hemisphere brain damage before birth in males may account for the same highly disproportionate male:female ratio seen in some other forms of CNS injury such as stuttering, dyslexia, hyperactivity, other learning disabilities and autistic disorder itself.
When was savant syndrome first discovered?
No doubt savants have been present throughout history. Although the term 'savant' was not applied to these special people until 1887 by Dr. J. Langdon Down, as described below, a report describing Jedediah Buxton, a prodigious lightning calculator who performed the most complicated multiplications and divisions swiftly in his head, appeared in a German Psychology Journal, Gnothi Sauton, as early as 1751.
Then in 1789, Dr. Benjamin Rush, often referred to as the father of American Psychiatry, described in detail the lightning calculating skills of Thomas Fuller "who could comprehend scarcely anything, either theoretical or practical, more complex than counting." When Fuller was asked how many seconds a man had lived who was 70 years, 17 days and 12 hours old he gave the correct answer of 2,210,500,800 in 90 seconds even correcting for the 17 leap years included.
But it was in 1887 that Dr. J. Langdon Down gave a series of lectures before the Medical Society of London based on his 30-year experience as Superintendent of the Earlswood Asylum. In those lectures he described 10 cases in careful detail of instances in which there was a striking contrast of superiority and disability in the same person. The special abilities included extraordinary musical, artistic, mathematical and mechanical skills always coupled with phenomenal memory in each and every case.
One individual built exquisite model ships from hand-fashioned parts and could recite complex texts verbatim. Another boy, after attending opera, would come away with a perfect recollection of all the arias. Another lad had memorized The Rise and Fall of the Roman Empire in its entirety and could recite it forward or backward. Still another young man could multiply multi-digit figures in his head as quickly as they could be written down on paper.
Dr. Down is best known for having named Down's Syndrome. But the cases of special abilities in otherwise severely disabled persons caught his attention as well and he coined the term idiot savant for these extraordinary individuals, linking those two words together because at that time the term idiot was an accepted scientific term for IQ below 25, and savant, or "knowledgeable person", was derived from the French word savoir meaning "to know". Dr. Down meant no harm by the term "idiot", and in fact he apologized for having to apply it — "I have no liking for the term. It is so frequently a term of reproach" he cautioned — but it was the accepted scientific term for a level of mental retardation at that time.
While descriptive perhaps, the term idiot savant was actually a misnomer since almost all reported cases since that time occur in persons with IQ above 40. In the interest of accuracy and dignity the term Savant Syndrome has been substituted and widely accepted. That term is preferable to autistic savant because only about one-half of persons with savant syndrome are autistic, and the other half have developmental disabilities or other forms of central nervous system injury or disease.
What is the relationship of savant syndrome to IQ?
When Dr. Down originally named the condition idiot savant, he linked its name with a classification of IQ of less than 25, but almost all reported cases have occurred in persons with an IQ above 40. However a low measured IQ score, or 'mental retardation' either as a symptom or separate disorder, is not what determines whether a person is or is not a savant. Instead the term savant syndrome encompasses a number of different mental disabilities including, but not limited to, the separate disorder of mental retardation itself. When applied to savant syndrome, the term 'mental disability' can include disorders as Autism, Asperger's, Hyperlexia or Williams Syndrome, for example.
In some of these persons measured IQ can be normal or even superior, although when that is the case, usually the IQ sub-scores show a wide scatter among the various sub-tests that make up the overall IQ test battery with some sub-tests showing severe limitations and other showing extremely high scores. Thus a low IQ score, while often present in savant syndrome, is not necessarily the case in all instances, and it is not a finding essential or requisite to savant syndrome. Some savants do score in the normal or superior range on commonly used IQ tests, or at least on some of the sub-tests that make up the overall IQ test battery.
IQ is a measure of so-called 'general intelligence'. While some scatter is common in most persons on the sub-tests of the IQ test battery, sub-test scores do tend to cluster in certain ranges for a given individual producing, when averaged, an overall 'general' intelligence score, or IQ. That IQ score does tend to be correlated with a general level of overall intellectual functioning. But the very wide scatter of abilities seen in some savants on the IQ sub-scores, which is much more pronounced than in most persons, has raised the question of whether it would be more accurate to view all persons as a series of multiple intelligences, rather than having what has been designated general intelligence, or IQ.
Indeed some investigators view savants as refuting the notion of 'general intelligence' and argue, instead, that each of us have multiple intelligences and testing & measurement of "IQ" in all persons should be revised to reflect that reality.
Further, in viewing 'mental retardation' one needs to differentiate between 'actual' retardation (measured IQ below 70) and 'functional' retardation. The latter can occur in someone with seemingly normal or even superior intellectual capacity whose mental disability, from whatever etiology, causes them to function at a much lower level over all than one might expect from estimated or even measured IQ.
It is not uncommon to see some autistic persons, for example, function at a superior level in some areas such as mathematics, verbal skills or memory, but be so severely disabled in other areas so as to 'function' at much lower level overall. The present IQ sub-tests, such as digit span, for example, are not sufficiently tailored to realistically assess certain areas of superior function in savants, and do need to be revised and tailored accordingly to be able to get a true measure of savant capabilities for comparative studies in the area of 'intelligence'.
In summary, measured IQ levels in savant syndrome most often are below 70. However while savant syndrome can occur in persons where Mental Retardation is the basic CNS disorder, savant syndrome can also be seen in persons with IO's below 70 as a finding or symptom where the basic developmental disorder is instead Autism, Asperger's, Hyperlexia, PDD or Williams Syndrome, for example, or a number of other conditions following CNS injury or disease.
While it is true that in most persons with savant syndrome measured IQ is below 70, savant syndrome includes a number of mental disorders in which IQ function, in scattered areas of functioning at least, can be normal or even superior. In short, savant syndrome is not synonymous with, nor limited to mental retardation, and in some persons with savant syndrome IQ can be in the normal, or even superior range.
Full Article
What is "autism"? What is the relationship of savant syndrome to autism?
The word 'autism' has lost its specificity. With respect to children the term 'autism' referred originally to a group of youngsters first described by Dr. Leo Kanner in 1943 to whom he attached the diagnosis of Early Infantile Autism. These were children who from a very early age showed "autistic" aloneness, mutism or language that failed to convey meaning to others, suspected deafness, a tendency to stare through but not at people, obsessive desire for sameness, use of the third person rather than personal pronouns, echolalia, literalness, fascination with spinning objects and rhythm, over-all serious-mindedness, phenomenal rote memory, and many repetitive and stereotypical behaviors, to name some of their characteristics and behaviors. They were children often described as being "in a world of their own".
Over the years, however, the term "autism" has been expanded to include what now is generally referred to as Autistic Disorder. This official diagnostic category includes, but is not now limited to, Kanner's original Early Infantile Autism group. In a state-wide survey in Wisconsin only about 25% of children with Autistic Disorder actually had Early Infantile Autism. The remainder had many of the same signs and symptoms of Early Infantile Autism, but with an onset either later in childhood, at about age 2 or 3, after a period of normal growth and development, or else they presented a clinical picture of autistic symptoms mixed with signs of other organic brain dysfunction.
Thus at the present time Autistic Disorder is a spectrum condition ranging in severity of disability from mild to profound. It is classified as a Developmental Disability, meaning it is in fact an organic or biological, not psychological, disorder that involves dysfunction of some portion of the central nervous system. In reality Autistic Disorder should probably more accurately be called "the Group of Autistic Disorders" because it appears those disorders stem from a variety of causes, and not from a single etiology. Also, those various disorders or sub-groups present with a variety of differing clinical symptoms and onsets, and have varying clinical courses and outcomes.
No single cause has been identified for either Autistic Disorder, or the sub-group of Early Infantile Autism, but it appears that some cases are genetic or in-born, and others involve, perhaps, some environmental, nutritional, metabolic, or other causes. The search for those causes is underway, as is the search for specific treatments for specific sub-groups of this over-all spectrum condition of Autistic Disorder.
Finally "autism" as a disorder needs to be separated from "autism" as a symptom. A number of CNS disorders such as Mental Retardation or other forms of CNS injury or disease, can have "autistic" symptoms or "autistic" behaviors as a part of the over-all clinical picture. But those autistic symptoms are not synonymous with, or the same as, Autistic Disorder as such.
Within the broad classification of Autistic Disorder, as pointed out above, approximately one in ten such persons has savant syndrome at a splinter skill, talented or prodigious level, with splinter skills being by far the most common presentation. Most clinicians include Asperger's Disorder in the spectrum of Autistic Disorders, and in persons with Asperger's Disorder savant skills are likewise quite common, at least at that 10% level.
Interestingly Dr. Hans Asperger, in Austria in 1944, when he first described the disorder that now bears his name, entirely unaware of Dr. Kanner's work in America, also applied the term "autistic" to his group of newly described patients, just as Dr. Kanner had applied that term to his group of youngsters only a year earlier in the United States.
In summary, Autistic Disorder appears in fact to be a group of disorders, one sub-group of which is Early Infantile Autism as originally described by Dr. Kanner. Onset can be from birth, or symptoms can occur after a period of normal development. The etiology is organic, not psychologic, and the causes are apparently several, rather than a single one. Within Autistic Disorder as many as 10% of such individuals have savant syndrome. However savant syndrome can also occur in conditions other than Autistic Disorder, although not as frequently. Therefore not all autistic persons are savants, and not all savants are autistic.
What causes savant syndrome?
While a number of theories have been put forth to date, no single theory can explain all savants. Some of those theories have included eidetic imagery or the related but separate phenomenon generally called photographic memory; inherited skills; sensory deprivation and sensory isolation with overcompensation in isolated skills, compensation, ritualistic practice and reinforcement of very narrow skills to offset and compensate for lack of more general capacity or intelligence; and phenomenal memorizing ability. There are problems with each of those theories. For example formal testing shows the presence of eidetic imagery in some, but not all, savants.
Two studies, one of 25 savants and another of 51 savants showed relatives with special skills or abilities in some, but not all cases; another study of 23 savants found only one family member with special skills. A number of studies, especially those looking at calendar calculating and prodigious musical ability, have demonstrated that savant abilities extend well beyond memorization alone as accounting for the special abilities, and have documented that literal, rote memory alone cannot provide a basis for the presence of extensive savant skills.
One theory, which quite consistently provides an increasingly plausible explanation for savant abilities in many cases, is left brain injury with right brain compensation. While left hemisphere/right hemisphere separation in the brain is an over-simplification, the fact is that the two brain hemispheres do tend to have specialized functions. The skills most often seen in savants are those associated with the right hemisphere, and those most lacking are those associated with the left hemisphere. A number of cases studied thus far do document left hemisphere damage on CT and MRI scans, and those imaging studies are also correlated with corresponding left-sided deficits on detailed neuropsychological testing.
Further, recent PET scan studies, in previously normal, non-disabled older persons where savant skills have emerged as a fronto-temporal dementia proceeds (see below), have shown defects in the left anterior temporal lobe. When those same PET scan studies were carried out on an 11 year old autistic, artistic savant, the same left anterior temporal lobe dysfunction was present. PET studies have also shown particular defects in left hemisphere function in autistic persons, with confirming left-sided findings on neuropsychological tests. Even before CT and PET imaging were available, pneumoencephalograms demonstrated left hemisphere abnormalities, particular in the left temporal lobe areas, in 15 of 17 autistic patients, four of whom had savant skills in music or mechanical interest areas.
In addition to left brain injury and right brain compensation, in the savant, it is postulated that there is corresponding damage to the higher level cognitive or semantic memory circuitry, with enhanced compensatory function in the lower level, more primitive, habit or procedural memory circuitry. This esults in reliance on the characteristic automatic memory — exceedingly deep but very, very narrow — habit memory seen in all savants. Such left brain damage/right brain compensation, coupled with semantic memory damage and procedural memory compensation, produces, then, the emergence of right brain skills coupled with automatic memory typically and characteristically seen in savant syndrome.
What is the 'treatment' for savant syndrome?
Savant Syndrome is not a disorder or disease by itself. It is, instead, a condition in which extraordinary skills and prodigious memory are grafted onto, or superimposed upon, a more basic brain dysfunction that rises from a developmental disability, or some other form of central nervous system disease or disorder. Therefore the 'treatment' for savant syndrome is the same treatment as that directed toward the more basic central nervous system disorder, such as Autism or Asperger's disorder, for example. Or in the case of persons with some other form of CNS injury, for example, it would be those treatment and rehabilitation efforts as directed toward overcoming the residual symptoms from such injury.
The special skills and abilities the savant demonstrates, however, can be used as a useful tool in the overall treatment and rehabilitation efforts directed toward overcoming or lessening the handicaps from the more basic developmental disorder, injury or disease. In many cases those extraordinary abilities can be used as a way of engaging the handicapped person in improved communication capacity, improved social interaction, and improved mastery of even daily living skills with movement, than, toward greater independence overall. In that manner the savant skills can serve as a 'conduit toward normalization' for the savant.
This paper has been excerpted in segments. To read the full report written by Dr. Treffert please click here
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