Idiot savants: rate of incidence

Do Savant Syndrome and Autism Spectrum Disorders Share Sex Differences? A Comprehensive Review

Savant syndrome was described before autism. However, they soon became closely associated, as many of their symptoms (intellectual disability, repetitive behaviors, alterations in social communication, and islets of abilities) overlap. Only a few women with autism have been diagnosed with savant syndrome. The theories or hypotheses that attempt to explain savant syndrome, which are common in autism, present differential treatment according to sex. We postulate that savant syndrome associated with autism as well as autism in general is underdiagnosed in women.

Neural mechanisms of savant calendar calculating in autism: an MEG-study of few single cases

This study contrasted the neurological correlates of calendar calculating (CC) between those individuals with autism spectrum disorder (ASD) and typically developing individuals. CC is the ability to correctly and quickly state the day of the week of a given date. Using magnetoencephalography (MEG), we presented 126 calendar tasks with dates of the present, past, and future. Event-related magnetic fields (ERF) of 3000ms duration and brain activation patterns were compared in three savant calendar calculators with ASD (ASDCC) and three typically developing calendar calculators (TYPCC). ASDCC outperformed TYPCC in correct responses, but not in answering speed. Comparing amplitudes of their ERFs, there was a main effect of group between 1000 and 3000ms, but no further effects of hemisphere or sensor location. We conducted CLARA source analysis across the entire CC period in each individual. Both ASDCC and TYPCC exhibited activation maxima in prefrontal areas including the insulae and the left superior temporal gyrus. This is in accordance with verbal fact retrieval and working memory as well as monitoring and coordination processes. In ASDCC, additional activation sites at the right superior occipital gyrus, the right precuneus, and the right putamen point to visual-spatial strategies and are in line with the preference of autistic individuals for engaging posterior regions relatively more strongly in various reasoning and problem solving tasks.

The mind of the mnemonists: an MEG and neuropsychological study of autistic memory savants

About 10% of autistic individuals exhibit some form of islets of abilities in the face of serious intellectual or mental disability ("savant syndrome"). The aim of this study was to investigate brain mechanisms in a sample of autistic subjects with outstanding memory. We investigated seven mnemonist savants with high-functioning autism spectrum disorder and seven matched controls with 151-channel whole-head magnetencephalography in a continuous old-new paradigm. They were presented with 300 pseudowords and 300 shapes and had to indicate by button press, whether the presented stimulus had been shown before. Unexpectedly, mnemonist savants did not perform better than controls, but were outperformed in the recognition of pseudowords. Accordingly, event-related magnetic fields elicited by pseudowords showed widespread old-new effects in controls, but not in savants. A source analysis of its early components revealed right occipital activation in savants, but left parietal activation in controls. This might be related to a visual processing style in mnemonist savants that proved to be inefficient in this task. During the possibly familiarity-based recognition of shapes, there were earlier and more widespread bilateral old-new effects in mnemonist savants, what might reflect their experience with figural material. In a neuropsychological test battery, mnemonist savants performed comparably to autistic people without special memory skills. However, a different factor structure of these tests pointed to a different organization of memory in mnemonist savants compared to controls that is characterized by its relative independence of general intelligence.

Relationship between special abilities and autistic-like traits in a large population-based sample of 8-year-olds

BACKGROUND

The raised incidence of special abilities or 'savant skills' among individuals with autism spectrum disorders (ASD) relative to other developmental disorders suggests an association between the traits characteristic of ASD and special abilities. The purpose of this study was to investigate the association between special abilities and ASD-like traits.

METHODS

This study compared the scores of 6,426 8-year-olds with and without parent-reported special abilities on a screening questionnaire for ASD-like traits in three areas: social interaction, communication, and restricted and repetitive behaviours and interests. Measures of IQ, sex, and socioeconomic status (SES) were also compared.

RESULTS

From parent report, children with special abilities showed significantly more ASD-like traits than those without such abilities. General intelligence did not mediate this relationship: IQ was found to be positively associated with ability, but negatively associated with ASD-like traits. Special abilities were more strongly associated with restricted/repetitive characteristics than with social or communication traits.

CONCLUSIONS

Results support the association between special abilities and ASD-like traits, and expand it to traits in the general population. The type of nonsocial traits most strongly associated with parental reports of special abilities suggests a link to a feature information processing style, or 'weak central coherence'.

Calendar calculating in savants with autism and healthy calendar calculators

BACKGROUND

Calendar calculation is the ability to quickly name the day that a given date falls on. Previous research has suggested that savant calendar calculation is based on rote memory and the use of rule-based arithmetic skills. The objective of this study was to identify the cognitive processes that distinguish calendar calculation in savant individuals from healthy calendar calculators.

METHOD

Savant calendar calculators with autism (ACC, n=3), healthy calendar calculators (HCC, n=3), non-savant subjects with autism (n=6) and healthy calendar calculator laymen (n=18) were included in the study. All participants calculated dates of the present (current month). In addition, ACC and HCC also calculated dates of the past and future 50 years.

RESULTS

ACC showed shorter reaction times and fewer errors than HCC and non-savant subjects with autism, and significantly fewer errors than healthy calendar calculator laymen when calculating dates of the present. Moreover, ACC performed faster and more accurate than HCC regarding past dates. However, no differences between ACC and HCC were detected for future date calculation.

CONCLUSIONS

The findings may imply distinct calendar calculation strategies in ACC and HCC, with HCC relying on calendar regularities for all types of dates and an involvement of (rote) memory in ACC when processing dates of the past and the present.

What aspects of autism predispose to talent?

In this paper, we explore the question, why are striking special skills so much more common in autism spectrum conditions (ASC) than in other groups? Current cognitive accounts of ASC are briefly reviewed in relation to special skills. Difficulties in 'theory of mind' may contribute to originality in ASC, since individuals who do not automatically 'read other minds' may be better able to think outside prevailing fashions and popular theories. However, originality alone does not confer talent. Executive dysfunction has been suggested as the 'releasing' mechanism for special skills in ASC, but other groups with executive difficulties do not show raised incidence of talents. Detail-focused processing bias ('weak coherence', 'enhanced perceptual functioning') appears to be the most promising predisposing characteristic, or 'starting engine', for talent development. In support of this notion, we summarize data from a population-based twin study in which parents reported on their 8-year-olds' talents and their ASC-like traits. Across the whole sample, ASC-like traits, and specifically 'restricted and repetitive behaviours and interests' related to detail focus, were more pronounced in children reported to have talents outstripping older children. We suggest that detail-focused cognitive style predisposes to talent in savant domains in, and beyond, autism spectrum disorders.

The savant syndrome: an extraordinary condition. A synopsis: past, present, future

Savant syndrome is a rare, but extraordinary, condition in which persons with serious mental disabilities, including autistic disorder, have some 'island of genius' which stands in marked, incongruous contrast to overall handicap. As many as one in 10 persons with autistic disorder have such remarkable abilities in varying degrees, although savant syndrome occurs in other developmental disabilities or in other types of central nervous system injury or disease as well. Whatever the particular savant skill, it is always linked to massive memory. This paper presents a brief review of the phenomenology of savant skills, the history of the concept and implications for education and future research.

Autism and pitch processing splinter skills

Autism is characterized by an uneven profile of cognitive abilities and population studies show that approximately 10 percent of diagnosed individuals possess a skill that is significantly better than would be predicted by global IQ. Recent evidence suggests that individuals with autism who possess special skills may represent a distinct genetic group within the autism spectrum. Intellectually high- and low-functioning children and adolescents with autism, together with age- and intelligence-matched comparison participants, completed two experiments that tested pitch discrimination and pitch memory within a visuo-spatial format. The analysis of the data from the studies showed that a subgroup of individuals with autism achieved performance scores that were between four and five standard deviations above the mean for the groups. Unlike comparison participants, their performance appeared to be independent of intelligence, musical training and experience. The findings were interpreted within the context of neuroconstructivist models of typical development and delayed language acquisition characteristic of autism and other neurodevelopmental disorders.

Annotation: the savant syndrome

BACKGROUND

Whilst interest has focused on the origin and nature of the savant syndrome for over a century, it is only within the past two decades that empirical group studies have been carried out.

METHODS

The following annotation briefly reviews relevant research and also attempts to address outstanding issues in this research area. Traditionally, savants have been defined as intellectually impaired individuals who nevertheless display exceptional skills within specific domains. However, within the extant literature, cases of savants with developmental and other clinical disorders, but with average intellectual functioning, are increasingly reported.

RESULTS

We thus propose that focus should diverge away from IQ scores to encompass discrepancies between functional impairments and unexpected skills. It has long been observed that savant skills are more prevalent in individuals with autism than in those with other disorders. Therefore, in this annotation we seek to explore the parameters of the savant syndrome by considering these skills within the context of neuropsychological accounts of autism. A striking finding amongst those with savant skills, but without the diagnosis of autism, is the presence of cognitive features and behavioural traits associated with the disorder.

CONCLUSIONS

We thus conclude that autism (or autistic traits) and savant skills are inextricably linked and we should therefore look to autism in our quest to solve the puzzle of the savant syndrome.

Exploratory subsetting of autism families based on savant skills improves evidence of genetic linkage to 15q11-q13

OBJECTIVE

Autism displays a remarkably high heritability but a complex genetic etiology. One approach to identifying susceptibility loci under these conditions is to define more homogeneous subsets of families on the basis of genetically relevant phenotypic or biological characteristics that vary from case to case.

METHOD

The authors performed a principal components analysis, using items from the Autism Diagnostic Interview, which resulted in six clusters of variables, five of which showed significant sib-sib correlation. The utility of these phenotypic subsets was tested in an exploratory genetic analysis of the autism candidate region on chromosome 15q11-q13.

RESULTS

When the Collaborative Linkage Study of Autism sample was divided, on the basis of mean proband score for the "savant skills" cluster, the heterogeneity logarithm of the odds under a recessive model at D15S511, within the GABRB3 gene, increased from 0.6 to 2.6 in the subset of families in which probands had greater savant skills.

CONCLUSIONS

These data are consistent with the genetic contribution of a 15q locus to autism susceptibility in a subset of affected individuals exhibiting savant skills. Similar types of skills have been noted in individuals with Prader-Willi syndrome, which results from deletions of this chromosomal region.

Das Savant-Syndrom: Eine Übersicht

Zusammenfassung. Theoretischer Hintergrund: Unter dem Savant-Syndrom versteht man das Auftreten eines herausragenden umschriebenen kognitiven Funktionsbereichs oder einer erstaunlichen Fertigkeit vorwiegend bei allgemeiner Intelligenzminderung. Fragestellung: Mit dieser Arbeit soll ein aktueller Überblick zur Beschreibung, Prävalenz, Neuropsychologie und Theoriebildung bezüglich des Syndroms gegeben werden. Methode: Auf der Basis historischer Berichte und derzeitiger empirischer Studien wird der Forschungsstand zum Savant-Phänomen dargestellt und diskutiert. Ergebnisse: Savants zeigen vor allem Kompetenzen in den Bereichen Gedächtnis, Musik, Zeichnen, Rechnen und Lesen. Spektakuläre Fälle dieser Inselbegabungen sind selten. Öfter anzutreffen sind Leistungen, die nur angesichts der vorherrschenden Psychopathologie der Person bemerkenswert sind. Savants sind unter autistisch beeinträchtigten Individuen vergleichbar häufig zu finden. Zum Verständnis der besonderen Fertigkeiten wurden in der Vergangenheit vielfältige, im Wesentlichen auf Fallstudien basierende Erklärungsansätze angeboten. Darunter die Involvierung von mechanischen Gedächtnisleistungen (rote memory), regelbasierten kognitiven Strategien, low-level-Informationsverarbeitung, repetitiv-übendem Verhalten, genetischen Faktoren und cerebralen Besonderheiten. Schlussfolgerungen: Angesichts der Heterogenität des Phänomens ist eine uneinheitliche Genese des Savant-Syndroms wahrscheinlich.

Incidence of Savant Syndrome in Finland

The general incidence of Savant Syndrome was assessed in Finland. First, a survey was made of all 583 facilities which served people with mental retardation. Second, letters asking for information regarding people with Savant Syndrome were published in two key Finnish journals of the field. We received reports of 45 cases of Savant Syndrome. This makes an incidence rate of 1.4 per 1,000 people with mental retardation. The most common form of exceptional skills was calendar calculation, followed by feats of memory.

The savant syndrome and autistic disorder

Savant syndrome, characterized by remarkable islands of mental ability in otherwise mentally handicapped persons, may occur in autistic as well as nonautistic individuals. Overall, approximately 10% of autistic persons exhibit savant abilities; roughly 50% of those with savant syndrome have autism, and the remaining 50% have other forms of developmental disability. Most commonly, savant syndrome takes the form of extraordinary musical abilities, but may also include calendar-calculation, artistic, mathematical, spatial, mechanical, and memory skills. While savant syndrome was first described more than a century ago, only recently have researchers begun to employ a more uniform nomenclature and more standardized testing in an effort to compare the abilities of savants with those of normal persons. Males show signs of savant syndrome approximately four times more often than females. Along with imaging study findings, this fact suggests the presence of a developmental disorder involving left-brain damage with right-brain compensation.

Savants, segments, art and autism

This study describes two experiments which investigate pattern construction by graphically gifted, autistic savants. We explore whether the notion of weak central coherence in autism might be extended to account for the relatively high frequency of savants among the autistic population. We also suggest that an awareness of constituent segments in wholes may be relevant to artistic talent in general.

The abilities of a musical savant and his family

The ability of a male autistic savant (TR) to play two unfamiliar piano pieces after listening to a tape-recording was tested, closely following the procedures of Sloboda, Hermelin, and O'Connor (1985). Other components of TR's musical ability--pitch recognition, improvisation, and ability to provide harmonic accompaniment--were also examined. TR's musical precocity was examined in relation to his general level of intellectual functioning as indexed by a battery of standardized psychological tests of intelligence, memory, reading, visual organization, and creativity. His parents and two male siblings also completed tests of intelligence. Results from psychometric testing indicated that TR has idiosyncratic levels of cognitive functioning with difficulties in verbal reasoning but high levels of concentration and memory. His speed of information processing, as indicated by Inspection Time, and was better than average. TR demonstrated perfect pitch recognition and other family members also demonstrated excellent relative pitch. TR's ability to recall and perform structured music within both the diatonic and whole-tone systems was exceptional but dependent upon his familiarity with musical structure and was therefore organized and rule-driven. Furthermore, TR demonstrated competence in improvisation and composition, albeit restricted by his adherence to structural representations of familiar musical rules.

Dysfunctional attention in autistic savants

A dysfunctional attention hypothesis of the basis of savant skills was tested with a series of computerized tasks that assessed the ability to divide, shift, direct, and sustain attention. Ten healthy men with pervasive developmental disorders and unusual calendar-calculating skill, and 10 age- and sex-matched controls were tested. There were four general findings. First, the savants and controls did not differ on a measure of visual sustained attention. Second, the savants failed to detect rare auditory targets significantly more than did the controls. Third, the savants were unable to efficiently divide their attention when required to detect both visual and auditory targets simultaneously. Finally, deficient orienting or a deficit in shifting selective attention from one stimulus location to another was evidenced in overall slower reaction times for the savants across tasks requiring shifts and redirecting of attention. This deficit was attributed to an inability to disengage attention as a result of deficient orienting and overselectivity.

Talents and preoccupations in idiots-savants

The question was asked whether a diagnosis of autism or a tendency to repetitive behaviour and preoccupation with a restricted area of interest, were crucial features of idiot-savant talents. Answers by caretakers to a questionnaire on these topics revealed that autistic and nonautistic savants resembled each other closely in preoccupation but differed from controls matched for IQ and diagnosis. In addition, the mentally handicapped showed fewer repetitive tendencies than did autistic controls. It is concluded that independent of diagnosis, preoccupations and repetitive behaviour appear to be closely associated with the manifestation of idiot-savant talents.

Exceptional calendar calculation ability after early left hemispherectomy

An 18-year-old male subject who had had his left hemisphere removed at age eight was better than chance at calculating the day of the week upon which dates in the past and future fell. He was able to describe his method of calculation, which relied upon both visual memory and serial calculations. The use of a serial calculation method was supported by evidence that both response time and accuracy were related to the distance in years from the current year. The use of both visual and verbal "working" memory was supported by interference effects from calendar calculations and delayed visual and verbal memory tasks. The case is discussed in terms of theories regarding similar calculation skills in idiot savants.

Low intelligence and special abilities

In summary, our research enables us to conclude that specific talents are found in people who differ widely in general intelligence levels and such talents should therefore be regarded as at least partly intelligence-independent. However, between normal and mentally handicapped populations and even within the idiot savant group, general cognitive capacity plays some part in determining the manner in which talents manifest themselves. Idiot savant special abilities can neither be regarded as the sole consequence of practice and training, nor are such skills based only on an efficient rote memory. Instead, idiots savants use strategies which are founded on the deduction and application of rules governing the material upon which their special ability operates. They also generate novel or new examples of such rule based structures just as we do in our use of language. Because of the much greater prevalence of idiots savants in the autistic than in the mentally handicapped population, some characteristic common to both autism and specific giftedness might be assumed. An obsessional pre-occupation with a limited section of the environment might be a common factor to both. It may be this rather than autism itself which is relevant to the idiot savant phenomenon.

On hermetic reading abilities

A review of the literature on hyperlexia suggests that the disorder is frequently associated with autism, that hermetic readers reach the lexicon via both the phonological and orthographic routes, and that the children derive meaning from print (notably, single words). In hyperlexia, as in other savant syndromes, the skills seemingly arise without a practice period and are not integrated with other areas of knowledge. A theory was advanced to account for the findings: Savants have dysfunctional procedural memory systems, though their declarative memories are relatively intact. The deficit in procedures is reflected in the difficulties savants have with routinized activities and in a dissociation of accessible knowledge from action. A disconnected declarative system manifests itself in the savant skill.

Idiot savant calendrical calculators: maths or memory?

Eight idiot savant calendrical calculators were tested on dates in the years 1963, 1973, 1983, 1986 and 1993. The study was carried out in 1983. Speeds of correct response were minimal in 1983 and increased markedly into the past and the future. The response time increase was matched by an increase in errors. Speeds of response were uncorrelated with measured IQ, but the numbers were insufficient to justify any inference in terms of IQ-independence. Results are interpreted as showing that memory alone is inadequate to explain the calendrical calculating performance of the idiot savant subjects.

Cognitive abilities and disabilities in infantile autism: a review

The literature on various aspects of learning and performance in autistic children is reviewed and interpreted as indicating very little that is specific to autism. Inadequate and inconsistent methodology precludes generalizations concerning the nature of the disorder. It is suggested that future research should be particularly concerned with controlling for developmental influences on performance, and with investigation of the higher functioning autistic children who are less governed by retardation factors. The current evidence is considered to support a hypothesis concerning abnormal hemisphere functioning in this group of children.