Reciprocate- acting the same way to someone as they acted to you.
Sentence: "Joe reciprocated to Bob for the candy."
Furtive- attempting to avoid notice or attention, typically because of guilt or or belief that discovery would lead to trouble.
Sentence: "While stealing the ruby Oscar was furtive when he took each step."
Naive- "Back when she was young and naive, she believed the cruel words people had spoken about the blacks."