According to Entertainment Weekly on Dec. 7, Peter Jackson gives an explanation of the mentality of Smaug in "The Hobbit: The Desolation of Smaug". Jackson considers the character more so like the "Hannibal Lector of the dragon world".
Though J.R.R. Tolkien's story has been around since 1937 and has been read countless times by fans of old who have been witnessed to the recognizable dialogue between Bilbo and Smaug. Jackson somehow how felt he contributed his own style of said dialogue to a theater audience.
Jackson also is aware that Smaug has a superior intellect compared to that of Bilbo who could so easily outwit Gollum.
"Smaug is super intelligent. Unlike Gollum who’s a messy, scattered kind of character, Smaug is smarter than Bilbo is. He’s very, very cunning. He plays psychological games with Bilbo. He’s really the Hannibal Lecter of the dragon world. All of that is to some degree in Tolkien’s book, but we really focused it razor-sharp for the movie.”
Another thing some may wonder is Smaug's obsession with the gold he's been sitting on top of all this time. Much like a dog that chases a squirrel, all this time it never gets caught. Then one day the squirrel is captured and now the dog cannot figure out what to do with it. This situation could be just as analogous to Smaug's as Jackson explains the villain's obsession with the acquired riches.
"We took the approach that Smaug is a paranoid psychopath. He has a lust for gold, but it’s a lust that he can’t explain. He’s not like a normal person who wants wealth for all the trappings of fast cars and yachts. Smaug doesn't have any of that, the poor guy. For 200 years, he’s been there on this pile of gold waiting for someone to come, just sitting there doing crossword puzzles and catching up on Breaking Bad seasons on Netflix. He hasn't got much else to do".
Most villains are human and when the acquire some kind of funds, they usually build a weapon of great power or attempt to take over the world. Smaug, however completely intelligent, would be incapable of creating a weapon of mass destruction. Not even an old-fashioned catapult.
Jackson also focused on the size of the beast as compared to what fans have been imagining the entire time when reading the book.
“I thought, ‘The one thing that would surprise me is if he lifts his head out of the gold and, instead of his head being two or three feet long, his head is the size of a bus and his body is the size of a 747. That would be pretty scary.’ So I thought, ‘OK, we’ll go with size".
"The Hobbit: The Desolation of Smaug" opens in theaters Dec. 13.