Earnest and serious: when should each be used?

Question

I've noticed there's a lot of overlap between the following words meaning "earnest" or "serious" when talking about a person:

• まじ
• 真面目{まじめ}
• 真剣{しんけん}
• 本気{ほんき}
• 正気{しょうき}: (This word really means "sane" I believe, but I'm including it as I think 「正気か？」 can translate to "are you serious?")
• 素直{すなお}: (I'm not sure whether this word meaning "honest" belongs here I but keep wondering what it's relationship to 真面目{まじめ} is when it means "obedient". I thought there might be some overlap in it's usage, e.g. 「素直な顔」 "obedient face" and 「真面目な顔」 "serious face". It could well be unrelated though.)

Would I be allowed to ask what the differences between these words are and when they're used?

Answer 1

• まじ colloquial and contracted form of 真面目.
• 真面目 'diligent, serious'
• 真剣 'serious, under one's best' implies some tension
• 本気 'one's best, mean it'
• 正気 'has not lost conscious (due to alchohol, drug, fainting, or extreme situation, etc.)'
• 素直 'obedient, open minded'

Answer 2

まじ

Never heard it used, except in 「まじで？」 which is sometimes written "本気". It means "aren't you joking" (see 本気)

真面目

真面目に勉強した。 He applied himself to studying.

真剣

真剣にやってくだい。 Do it conscientiously, won't you?

本気

本気で言った。 He wasn't joking when he said that.

正気

I never heard/used it enough to answer…

素直

Unrelated to the above… It means docile, honest, compliant…