In the BBC reworking of Sherlock Holmes, starring Benedict Cummerbund and Martin Freeman, the writers have Sherlock describe himself as a ‘high functioning sociopath’. Elsewhere in the series there are mutterings of autism and Asperger’s from his sidekick Dr. Watson. But would Conan Doyle, a medical man himself, have agreed with these diagnoses? And exactly how would modern psychologists explain the enigma that is Sherlock Holmes? Lori Boul shares her thoughts.