I guess I'll never find out if the rumor is true that George Lucas hates directing actors, but anyone who doubts his ability to get good performance out of actors should see "THX 1138" and "American Graffiti". Especially "THX 1138". Here is a story in which androids co-exist with humans who themselves act robotically, yet Lucas is able to inject "warm blood" into the characters played by Robert Duvall and Maggie McOmie who are required by the script to show minimum emotions as they are the enslaved citizens in a futuristic totalitarian state. Lucas had to be engaged with the actors on the set in order to extract intense Bergmanesque (pardon the expression) acting from these actors who had their heads shaved and wore only blinding-white mental-ward-regulars' uniforms.
Between 1971 when this picture came out and 1977 when Star Wars reinvented the modern sci-fi genre, Lucas only made one movie, "American Graffiti". Something just didn't seem right. If you were a so-called "studio honcho" in 1971 and happened to see this movie and could not conclude that this USC film school "kid" is enormously talented, you did not deserve the title.
"THX 1138" was partially filmed in the then-still-unfinished San Francisco subway system where Lucas brilliantly created the atmosphere of a cruel futuristic society in which the empty slogan of "Work and Be Happy" is repeated over and over. I've heard some people suggest that "THX" means "Thinks" because the protagonist, played by Robert Duvall, defies the "no thinking" order from the authority, but in the imdb.com trivia section, someone theorizes that "THX" sounds like "Sex" when pronounced by his secret lover (sex is banned in the fictional dictatorship). Another one claims that "THX 1138" is merely Lucas's old home phone number. Lucas apparently has the last laugh, as he later maximized the commercial potential of the memorable title by turning it into the brand name/logo of a popular movie theater sound system.