Actually, I would choose Literature. Psychology is classified as a soft subject (meaning it's not as respected much) and believe it or not, many people do poorly in it because there is a lot of content you need to cram in, which I've heard is usually boring.
Choosing Literature allows you have an essay-based subject which your choices are currently lacking in and unlike Psychology, Literature is a facilitating subject, being more respected. Having your subjects all Science-based may be a little boring, so it's best to show diversity.