Characteristics

A pervasive developmental disorder, Asperger syndrome is distinguished by a pattern of symptoms rather than a single symptom. It is characterized by qualitative impairment in social interaction, by stereotyped and restricted patterns of behaviour, activities and interests, and by no clinically significant delay in cognitive development or general delay in language. Intense preoccupation with a narrow subject, one-sided verbosity, restricted prosody, and physical clumsiness are typical of the condition, but are not required for diagnosis.

Social interaction

The lack of demonstrated empathy is possibly the most dysfunctional aspect of Asperger syndrome. Individuals with AS experience difficulties in basic elements of social interaction, which may include a failure to develop friendships or to seek shared enjoyments or achievements with others (for example, showing others objects of interest), a lack of social or emotional reciprocity, and impaired nonverbal behaviours in areas such as eye contact, facial expression, posture, and gesture.

Unlike those with autism, people with AS are not usually withdrawn around others; they approach others, even if awkwardly. For example a person with AS may engage in a one-sided, long-winded speech about a favourite topic, while misunderstanding or not recognizing the listener's feelings or reactions, such as a need for privacy or haste to leave. This social awkwardness has been called "active but odd".[1] This failure to react appropriately to social interaction may appear as disregard for other people's feelings, and may come across as insensitive.

The cognitive ability of children with AS often allows them to articulate social norms in a laboratory context, where they may be able to show a theoretical understanding of other people's emotions; however, they typically have difficulty acting on this knowledge in fluid, real-life situations.[5] People with AS may analyze and distil their observation of social interaction into rigid behavioural guidelines, and apply these rules in awkward ways, such as forced eye contact, resulting in a demeanour that appears rigid or socially naive. Childhood desire for companionship can become numbed through a history of failed social encounters.

The hypothesis that individuals with AS are predisposed to violent or criminal behaviour has been investigated but is not supported by data. More evidence suggests children with AS are victims rather than victimizers. A 2008 review found that an overwhelming number of reported violent criminals with AS had coexisting psychiatric disorders such as schizoaffective disorder.

Restricted and repetitive interests and behaviour

People with Asperger syndrome often display behaviour, interests, and activities that are restricted and repetitive and are sometimes abnormally intense or focused. They may stick to inflexible routines, move in stereotyped and repetitive ways, or preoccupy themselves with parts of objects.

Pursuit of specific and narrow areas of interest is one of the most striking features of AS. Individuals with AS may collect volumes of detailed information on a relatively narrow topic such as dinosaurs or members of congress, without necessarily having genuine understanding of the broader topic. For example, a child might memorize camera model numbers while caring little about photography. This behaviour is usually apparent by grade school, typically age 5 or 6 in the United States. Although these special interests may change from time to time, they typically become more unusual and narrowly focused, and often dominate social interaction so much that the entire family may become immersed. Because narrow topics often capture the interest of children, this symptom may go unrecognised.

Stereotyped and repetitive motor behaviours are a core part of the diagnosis of AS and other ASDs. They include hand movements such as flapping or twisting, and complex whole-body movements. These are typically repeated in longer bursts and look more voluntary or ritualistic than tics, which are usually faster, less rhythmical and less often symmetrical.

Speech and language

Although individuals with Asperger syndrome acquire language skills without significant general delay and their speech typically lacks significant abnormalities, language acquisition and use is often atypical. Abnormalities include verbosity, abrupt transitions, literal interpretations and miscomprehension of nuance, use of metaphor meaningful only to the speaker, auditory perception deficits, unusually pedantic, formal or idiosyncratic speech, and oddities in loudness, pitch, intonation, prosody, and rhythm.

Three aspects of communication patterns are of clinical interest: poor prosody, tangential and circumstantial speech, and marked verbosity. Although inflection and intonation may be less rigid or monotonic than in autism, people with AS often have a limited range of intonation: speech may be unusually fast, jerky or loud. Speech may convey a sense of incoherence; the conversational style often includes monologues about topics that bore the listener, fails to provide context for comments, or fails to suppress internal thoughts. Individuals with AS may fail to monitor whether the listener is interested or engaged in the conversation. The speaker's conclusion or point may never be made, and attempts by the listener to elaborate on the speech's content or logic, or to shift to related topics, are often unsuccessful.

Children with AS may have an unusually sophisticated vocabulary at a young age and have been colloquially called "little professors", but have difficulty understanding figurative language and tend to use language literally. Children with AS appear to have particular weaknesses in areas of non literal language that include humour, irony, and teasing. Although individuals with AS usually understand the cognitive basis of humour they seem to lack understanding of the intent of humour to share enjoyment with others. Despite strong evidence of impaired humour appreciation, anecdotal reports of humour in individuals with AS seem to challenge some psychological theories of AS and autism.

Other

Individuals with Asperger syndrome may have signs or symptoms that are independent of the diagnosis, but can affect the individual or the family. These include differences in perception and problems with motor skills, sleep, and emotions.

Individuals with AS often have excellent auditory and visual perception. Children with ASD often demonstrate enhanced perception of small changes in patterns such as arrangements of objects or well-known images; typically this is domain-specific and involves processing of fine-grained features. Conversely, compared to individuals with high-functioning autism, individuals with AS have deficits in some tasks involving visual-spatial perception, auditory perception, or visual memory. Many accounts of individuals with AS and ASD report other unusual sensory and perceptual skills and experiences. They may be unusually sensitive or insensitive to sound, light, touch, texture, taste, smell, pain, temperature, and other stimuli, and they may exhibit synesthesia; these sensory responses are found in other developmental disorders and are not specific to AS or to ASD. There is little support for increased fight-or-flight response or failure of habituation in autism; there is more evidence of decreased responsiveness to sensory stimuli, although several studies show no differences.

Hans Asperger's initial accounts and other diagnostic schemes include descriptions of physical clumsiness. Children with AS may be delayed in acquiring skills requiring motor dexterity, such as riding a bicycle or opening a jar, and may seem to move awkwardly or feel "uncomfortable in their own skin". They may be poorly coordinated, or have an odd or bouncy gait or posture, poor handwriting, or problems with visual-motor integration. They may show problems with proprioception (sensation of body position) on measures of apraxia (motor planning disorder), balance, tandem gait, and finger-thumb apposition. There is no evidence that these motor skills problems differentiate AS from other high-functioning ASDs.

Children with AS are more likely to have sleep problems, including difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings AS is also associated with high levels of alexithymia, which is difficulty in identifying and describing one's emotions. Although AS, lower sleep quality, and alexithymia are associated, their causative relationship is unclear.

As with other forms of ASD, parents of children with AS have higher levels of stress.