Leslie completed his undergraduate degree in Psychology and Linguistics at the University of Edinburgh in 1974 and received his D.Phil.
For a number of years he was a Medical Research Council Senior Scientist at the University of London.
In 2005 he gave the XIII Kanizsa Memorial Lecture at the University of Trieste and in 2006 he was the inaugural recipient of the Ann L. Brown Award for Excellence in Developmental Research.
[3] Leslie was a member of the Cognitive Development Unit (CDU) in London who proposed the theory of mind impairment in autism.
He has contributed a number of influential experimental studies and theoretical ideas on the perception of cause and effect, object tracking, and agent detection in infancy, the developmental role of modularity of mind, and the Theory of Mind Mechanism (ToMM) in the development of social cognition and its impairment in autism.