Joaquin Phoenix on how he cracked Joker's signature laugh

Joaquin Phoenix says he based the signature laughter of iconic DC villain The Joker on a neurological disorder known as Pathological Laughter and Crying (PLC).

The condition is characterised by inappropriate and involuntary laughing and crying due to a nervous system disorder.

Phoenix, who is set to star as the Clown Prince of Crime in the eponymous film, said he watched videos of people suffering from the condition as part of his preparation.

"I started (with the laugh). I watched videos of people suffering from pathological laughter, a neurological disorder that makes individuals laugh uncontrollably," the actor told Italian magazine Il Venerdi.

Phoenix follows the likes of Jack Nicholson, Mark Hamill, Heath Ledger and Jared Leto with his portrayal of the Joker in the Todd Philips-directed movie.

Also featuring Zazie Beetz, Robert De Niro and Marc Maron, "Joker" will have its world premiere at the Venice Film Festival later this month. It releases worldwide in October.