The Defining Characteristics of Autism

There are no medical tests for autism.

By Gladys Pollack

According to Autism Treatment Services of Canada, an accurate diagnosis of autism must be based on observation of an individual's communication, behaviour and developmental levels. The word “syndrome” is applied to autism by diagnosticians because the symptoms are many and varied. People with autism are a very heterogeneous group, says Dave Mikkelsen, executive director of Autism Treatment Services.

The Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) established by the American Psychiatric Association has established the basic defining characteristics of the syndrome of autism. They include the following:

1. Impaired Development of Reciprocal Social Interaction

Individuals with autism do not develop normal interactive social relationships with others. Many times they are described as living in a world of their own. They may avoid both eye contact as well as physical contact with others. Their social skills are poorly developed and social interactions, when they do occur, are mechanical and stilted.

2. Impairment in Communication and Imaginative Activity

Impairment affects both verbal and nonverbal skills. Approximately 40 to 50 percent of autistic people never develop functional language use. When speech and language do develop, they are qualitatively different from that of normal children or even children with language disorders. “Echolalia” refers to the parrot-like way autistic individuals repeat what has been said to them. Pronoun reversal is common in the autistic population. The autistic individual may be unable to label objects or understand abstract speech. They may develop unusual speech patterns or utterances that are apparently uncommunicative but whose meaning is clear to those familiar with the individual. Abnormal speech melody, or dysprosody, is also a symptom of autism. Speech, when present, may be characterized by rises at the end of sentences, or conversely, a monotonous tonal quality. Nonverbal communication through facial expression and gesture is often absent or situationally inappropriate.

Impaired imaginative activity refers to the inability to engage in imaginative or symbolic play.

3. Markedly Restricted Repertoire of Activities and Interests

This refers to the inability to relate normally to objects and events in the environment. Autistic individuals frequently are obsessive/compulsive about the state of their surroundings. They may require certain elements to remain the same, from the positions of objects to the order of their routines. This inflexibility can lead to a very rigid lifestyle. Autistic people may develop bizarre attachments to objects, such as a piece of string, or they may become preoccupied with a particular aspect of an object. Frequently they may engage in stereotypical motor behaviours such as hand flapping and rocking. They may experience a profoundly restricted range of interests and a preoccupation with one narrow interest.

Other associated features include:

Abnormal Cognitive Development

The cognitive development of the autistic population is generally uneven and a large proportion are mentally handicapped. However, it is not uncommon for an autistic person to have an exceptional ability in one or more areas.

Abnormal Posture and Motor Behaviour

Often, autistic individuals engage in stereotypical motor behaviours such as hand flapping, rocking or lunging. They may exhibit unusual body postures (walk on their tiptoes) or hand postures.

Odd Responses to Sensory Input

There is great variation in their responses to sensory stimulation and responses may be inconsistent. Sometimes a loud noise may be totally ignored, while at other times a whisper may elicit a sensitive response.

Abnormality in Eating, Drinking and Sleeping

Some autistic individuals may restrict their diet to a few different foods. Some may refuse to eat items with a particular colour. Individuals with autism frequently have disturbed sleep patterns.

Abnormalities of Mood

People with autism may have erratic emotional responses, exhibiting great variation in their emotions or inappropriate reactions to their environment. Some may show little variation in their emotions.

Self-injurious Behaviour

Head-banging, biting of hands or wrists, head and elbow slapping, hair pulling and scratching are often observed in the autistic population. There is a great variation in the intensity of this self-injurious behaviour.

For more information, visit Autism Treatment Services of Canada/Association Canadienne pour L' Obtenton de Services aux Personnes Autistiques at:

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