The autistic disorder belongs to the pervasive developmental disorders that usually begin in the early childhood and affect large areas of the child's development. The term spectrum disorder is used because the disorder is highly variable.
Impairments are mostly in the areas of communication, social interaction, play behavior and the area of interests.
Many children have a delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime). For some kids its even difficult to express their basic needs, which can lead to frustration and aggressive behaviors. Children with adequate speech, have impairments in the ability to initiate or sustain a conversation with others. They often have a stereotyped and repetitive use of language (echolalia). Meaning, the children repeat what they have just heard from another person or they repeat previously heard sequences of radio plays or films again and again.
Impairments are usually found in social interactions. Many children show little or no interest in their peers. During social interaction they lack multiple nonverbal behaviors, such as eye-to-eye gaze, facial expression, body postures, and gestures to regulate social interaction. Most of the time they lack to share enjoyment, interests, or achievements with other people (e.g., by a lack of showing, bringing, or pointing out objects of interest). Emotions of others are often not recognized and therefore an appropriate response is lacking. For many persons it is difficult to share their feelings or interests with others. Also learning from interactions with others is often severely limited due to difficulties in the area of motor imitation.
Restricted, repetitive, and stereotyped patterns of behavior, interests, and activities:
Abnormalities are also usually found in the play behavior and interests of the children. Often you can find a preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus (e.g. lining up things, interests in schedules or specific topics such as trains, bells or astronomy). Some of the kids are interested in parts of objects only (e.g. turning the wheels of a car) and many of them are lacking symbolic play. Many children engage in stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting or complex whole-body movements like rocking). And some of them display inflexible adherence to specific, nonfunctional routines or rituals.