This thesis illustrates that Kanner held an explicitly descriptive frame of reference toward his eleven child patients, their parents, and autism. Adolf Meyer, his mentor at Johns Hopkins, trained him to make detailed life-charts under a clinical framework called psychobiology. By understanding that Kanner was a psychobiologist by training, I revisit the original definition of autism as a category of mental disorder and restate its terms. This history illuminates the theoretical context of autism's discovery and has important implications for the first definition of autism amidst shifting theories of childhood mental disorders and the place of the natural sciences in defining them.

Leo Kanner studied and described early infantile autism in humans in the US during the twentieth century. Though Eugen Bleuler first coined the term autism in 1910 as a symptom of schizophrenia, Kanner helped define autism as a disease concept separate from schizophrenia. He helped found an early child psychiatry department in 1930 at the Johns Hopkins University Hospital in Baltimore, Maryland. Kanner revised criteria for diagnosing autism, beginning with his article Autistic Disturbances of Affective Contact in 1943, and he helped reclassify autism as a disorder caused by defective neurological development.

Bernard Rimland studied autism in children in the United States in the second half of the twentieth century. His early research in the 1950s and into the 1960s led him to assert that infantile autism was a neurodevelopmental disorder, or one that is caused by impairments in the growth and development of the brain or central nervous system. Rimland's assertion that infantile autism was a neurodevelopmental disorder contradicted another theory at that time that the condition resulted from emotionally cold parenting. Rimland spent much of his career as a psychology researcher for the United States Navy in Point Loma, California, but in his spare time he researched and wrote about autism, and he advocated for children with autism and their families.

Infantile Autism: The Syndrome and Its Implications for a Neural Theory of Behavior (hereafter Infantile Autism) is a book written by Bernard Rimland, published in 1964. The book proposed a theory to explain the causes of autism. The book also synthesized research into autism and used Rimland's neural theory, described in the book, as a theory to explain some aspects of behavior, intelligence, and abnormality. Moreover, Infantile Autism contributed to a debate between Rimland and child psychologist Bruno Bettelheim in the 1960s over whether autism was caused by upbringing (see refrigerator mother theory) or by impaired brain development. Rimland's book convinced many autism researchers to look for abnormal psychological development.

Leo Kanner published Autistic Disturbances of Affective Contact in 1943 in the journal Nervous Child. This article described the cases of eleven children with autism. Kanner described the behavior and upbringing of each child, aged two to eight, as well as the educational backgrounds of the children's. Though Eugen Bleuler, a professor of psychiatric at the University of Z rich and director of the Burgh lzli Asylum in Z rich in Z rich, Switzerland from 1898 to 1927, was first to use the term autism to describe of a symptom of schizophrenia, scientists cite Kanner's article as the first description of autism as a unique disease concept distinct from schizophrenia. One of the most cited articles about autism in the twentieth century, this article was the first to demarcate Kanner syndrome, which later called childhood autism. Researchers, including Kanner, eventually treated early infantile autism as a disorder resulting from abnormal development of the autistic children's brains.

In 1943, child psychiatrist Leo Kanner in the US gave the first account of Early Infantile Autism that encouraged psychiatrists to investigate what they called emotionally cold mothers, or refrigerator mothers. In 1949, Kanner published Problems of Nosology and Psychodynamics of Early Infantile Autism. In that article, Kanner described autistic children as reared in emotional refrigerators. US child psychiatrists claimed that some psychological or behavioral conditions might have origins in emotional or mental stress, meaning that they might be psychogenic. Kanner described autism's cause in terms of emotional refrigeration from parents into the early 1960s, often attributing autism to the lack of parental warmth. In the 1960s, Bernard Rimland in the US and Bruno Bettelheim in Austria disagreed on the role of psychogenesis in autism. Rimland suggested that autism's cause was rooted in neurological development, while Bettelheim continued to emphasize the role of nurturing during early childhood. Nevertheless, many mothers reported that they felt a deep sense of anguish and resentment toward child psychiatrists who often made them feel as if they were to blame for their children's autism.

Hans Asperger studied mental abnormalities in children in Vienna, Austria, in the early twentieth century. Asperger was one of the early researchers who studied the syndrome that was later named after him, Asperger's Syndrome. Asperger described the syndrome in his 1944 publication Die Autistischen Psychopathen im Kindesalter (Autistic Psychopathy in Childhood). At that time, the syndrome was called autistic psychopathy, and Asperger noted that characteristics of the syndrome included lack of sympathy, one-sided conversations, and difficulty forming friendships. Asperger's work led to the recognition of Asperger's Syndrome as a disorder that results from abnormal development, and the syndrome was later classed on the autism spectrum.

Paul Eugen Bleuler studied autism and schizophrenia, among other psychiatric disorders, throughout continental Europe in the early twentieth century. Bleuler worked as a psychiatrist caring for patients with psychiatric disorders at a variety of facilities in Europe. In 1908, Bleuler coined the term schizophrenia to describe a group of diseases that cause changes in thought processes and behavior in humans as well as difficulties relating to the world. Bleuler also introduced the concepts of autism, which he defined as a disconnect from the outside world, and ambivalence, which he defined as the coexistence of conflicting ideas in one’s mind. Bleuler’s concepts enabled later researchers, such as Bernard Rimland, to study the causes of those disorders, and to suggest that abnormal development of fetal brains potentially caused those disorders.