He explored both prenatal and post natal developmental issues and touched upon developmental aspects that are experience-expectant (visual experiences, hearing experiences, language learning) and experience-dependent (unique to individual such as reading, singing etc).
While he touched upon a variety of Pervasive Developmental Disorders (PDDs), his main focus was on Autism spectrum disorders that occur in 1 in 1000 individuals with males being much more susceptible to it than females (4-5:1). About 75% of them have mental retardation and often exhibit restricted, repetitive, stereotyped behaviour. There was a good discussion about autistic savants, GABAergic behaviour being local vs global etc and one of the inputs was that even now the best therapy for autism continues to be behavioural and needs strong commitment from parents as well.