Quote from : The Secret Life of Marilyn Monroe Book

She had told Kazan that she was bored with the roles she was playing because so many of them had been basically the same kind of empty-headed characterization. She wanted nothing ore than to challenge herself with more complex parts--and also wanted others to think of her as being more than a caricature. ... Anytime she had an opportunity to broaden her mind, she wanted to take advantage of it.