1) Artless simplicity 2) Artlessness 3) Credulity 4) Credulous quality 5) Credulousness 6) French word used in English 7) Girlish quality 8) Green state 9) Guilelessness 10) Inexperience 11) Innocence 12) Innocent nature 13) Lack of guile 14) Lack of seasoning 15) Lack of sophistication 16) Lack of worldliness 1) Artlessness 2) Credulousness 3) Gullibility 4) Ingenuousness 5) Innocence 6) Naiveness 7) Naivety 
• (n.) Native simplicity; unaffected plainness or ingenuousness; artlessness. • (n.) Native simplicity; unaffected plainness or ingenuousness; artlessness.
Na`ïve`té' noun [ French See Naïve , and confer Nativity .] Native simplicity; unaffected plainness or ingenuousness; artlessness. « A story which pleases me by its naïveté -- that is, by its unconscious ingenuousness.» De Quincey. 
[n] - lack of sophistication or worldliness
naivety noun lack of sophistication or worldliness
the quality or state of being naive; natural or artless simplicity. · a naive action, remark, etc.
[SAT terms] lack of sophistication or worldliness