I A Total of 6 (or more items from (A), (B) and (C), with at least 2 from (A) and one each from (B) and (C)

1. Qualitative impairments in social interaction, as manifested by at least 2 of the following:-

1. Marked impairments in the use of multiple non-verbal behaviours such as eye-to-eye gaze, facial expression, body posture and gestures to regulate social interaction

2. Failure to develop peer relationships appropriate to developmental level - a failure to develop any friendship beyond the most superficial acquaintance.
3. A lack of spontaneous seeking to share enjoyment, interests or achievements with other people - eg: by a lack of showing, bringing or pointing out objects of interest to other people (joint-attentional behaviours which occur in normal babies between 9 and 14 months)
4. Lack of social or emotional reciprocity - eg: not actively participating in simple social play or games (such as turn-taking), preferring solitary activities or involving others only as ‘tools’ or ‘mechanical aids’ (According to Leo Kanner, 1943, and Simon Baron-Cohen, 1988, a lack of empathy is often seen as the central feature of the social deficit)

B.   Qualitative impairments in communication, as manifested by at least one of the following:-

1. 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

2. In individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others
3. Stereoptyped and repetitive use of language or idiosyncratic language
4. Lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level (Alan Leslie, 1987, adds the lack of symbolic play to this criterion while Baron-Cohen, 1987, talks about engaging in play which is often lacking in creativity and imagination - such ‘pretend play’ normally occurring in normal children between 14 and 18 months)

C.   Repetitive and stereotyped patterns of behaviour, interests and activities, as manifested by at least 2 of the following:-

1. Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus

2. Apparently inflexible adherence to specific, non-functional routines or rituals
3. Stereotyped and repetitive motor movements - eg: hand or finger flapping or twisting or complex whole body movements
4. Persistent preoccupation with parts of objects

II Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years:

1. Social interaction

2. Language as used in social communication
3. Symbolic or imaginative play

III The disturbance is not better accounted for by Rett’s Disorder

Based on DSM IV-TR (2000)