Here’s the 1980 definition of Infantile Autism as it appeared in DSM-III.
A. Onset before 30 months of age
B. Pervasive lack of responsiveness to other people
C. Gross deficits in language development
D. If speech is present, peculiar speech patterns such as immediate and delayed echolalia, metaphorical language, pronominal reversal
E. Bizarre responses to various aspects of the environment, e.g., resistance to change, peculiar interest in or attachments to animate or inanimate objects
F. Absence of delusions, hallucinations, loosening of associations, and incoherence as in Schizophrenia.
And here is how the equivalent items are phrased in the current version, DSM-5, under Autism Spectrum Disorder:
A. Symptoms must be present in the early developmental period (but may not become fully manifest until social demands exceed limited capacities or may be masked by learned strategies later in life).
B. Deficits in social-emotional reciprocity must be present (or have been present earlier in development). However, these can range from abnormal social approach and failure of normal back and forth conversation through reduced sharing of interests, emotions, and affect and response to total lack of initiation of social interaction
C. ASD can be diagnosed with or without accompanying language impairment
D. “Peculiar speech patterns” are not required for a diagnosis. However, echolalia and idiosyncratic phrases are considered examples of Stereotyped or repetitive movements, use of objects, or speech – one of four nonsocial features (see E below)
E. Any two of the following must be present (currently or earlier in development): (1) Stereotyped use of objects; (2) Insistence on sameness, inflexible adherence to routines, or ritualized patterns of verbal or nonverbal behaviour; (3) Highly restricted, fixated interests that are abnormal in intensity or focus; (4) Hyper- or hypo-reactivity to sensory input or unusual interest in sensory aspects of the environment
F. Hallucinations and delusions, which are defining features of schizophrenia, are not features of ASD
it’s fair to say that the majority of people whom we would today think of as being “on the spectrum” would not have come close to a diagnosis in the 1980s.