Savant syndrome

Savant syndrome is a condition in which a person with a mental disability, such as an autism spectrum disorder, demonstrates profound and prodigious capacities or abilities far in excess of what would be considered normal. People with savant syndrome may have neurodevelopmental disorders, notably autism spectrum disorders, or brain injuries. The most dramatic examples of savant syndrome occur in individuals who score very low on IQ tests, while demonstrating exceptional skills or brilliance in specific areas, such as rapid calculation, art, memory, or musical ability. Although termed a syndrome, it is not recognized as a mental disorder nor as part of a mental disorder in medical manuals such as the ICD-10 or the DSM-5.

Another form of savant syndrome is acquired savant syndrome, in which a person acquires prodigious capabilities or skills following dementia, a head injury or severe blow to the head, or other disturbance. This syndrome is rarer, with a study by Darold Treffert in 2010 showing that in a registry of 319 known savants, only 32 had acquired savant syndrome.

Characteristics

Savant skills are usually found in one or more of five major areas: art, musical abilities, calendar calculation, arithmetic, and spatial skills. The most common kind of autistic savants are calendrical savants, "human calendars" who can calculate the day of the week for any given date with speed and accuracy. Memory feats are the second most common savant skill in a survey.

Approximately half of savants are autistic; the other half often have some form of central nervous system injury or disease. Among those with autism, it is estimated that 10% have some form of savant abilities.

Mechanism

Psychological

No widely accepted cognitive theory explains savants' combination of talent and deficit. It has been suggested that individuals with autism are biased towards detail-focused processing and that this cognitive style predisposes individuals either with or without autism to savant talents. Another hypothesis is that savants hyper-systemize, thereby giving an impression of talent. Hyper-systemizing is an extreme state in the empathizing–systemizing theory that classifies people based on their skills in empathizing with others versus systemizing facts about the external world. Also, the attention to detail of savants is a consequence of enhanced perception or sensory hypersensitivity in these unique individuals. It has also been confirmed that some savants operate by directly accessing low-level, less-processed information that exists in all human brains that is not normally available to conscious awareness.

Neurological

Savant syndrome results from damage to the left anterior temporal lobe, an area of the brain key in processing sensory input, recognizing objects and forming visual memories. Savant syndrome has been artificially replicated using transcranial magnetic stimulation to temporarily disable this area of the brain.

Epidemiology

See also: Epidemiology of autism

There are no objectively definitive statistics about how many people have savant skills. The estimates range from "exceedingly rare" to one in ten people with autism having savant skills in varying degrees. A 2009 British study of 137 parents of autistic children found that 28% believe their children met the criteria for a savant skill, defined as a skill or power "at a level that would be unusual even for 'normal' people". As many as 50 cases of sudden or acquired savant syndrome have been reported.

Males with savant syndrome outnumber females by roughly 6:1, slightly higher than the sex ratio disparity for autism spectrum disorders of 4.3:1.

History

The term idiot savant (French for "learned idiot" or "knowledgeable idiot") was first used to describe the condition in 1887 by John Langdon Down, who is known for his description of Down syndrome. The term idiot savant was later described as a misnomer because not all reported cases fit the definition of idiot, originally used for a person with a very severe intellectual disability. The term autistic savant was also used as a description for the disorder. Like idiot savant, the term came to be considered a misnomer because only half of those who were diagnosed with savant syndrome were autistic. Upon realization of the need for accuracy of diagnosis and dignity towards the individual, the term savant syndrome became widely accepted terminology.

See also

• Asperger syndrome
• Ideasthesia
• Creativity and mental illness
• Hyperthymesia