C.Z.
I am reading a book right now that has a good chapter on why children lie - NurtureShock by PO Bronson & Ashley Merryman. "We may treasure honesty, but the research is clear. Most classic strategies to promote truthfulness just encourage kids to be better liars." Studies show a 4 yr old will lie about once every 2 hrs and a 6 yr old will lie about once an hour! Most lies are to cover up a trangression - the kid does something they shouldn't and then to stay out of trouble denies doing it. Children are much more disapproving of lies and liars than adults are. Lying is actually a developmental milestone - it's related to intelligence. As kids get older the reasons for lying get more complex - lie to spare a friend's feelings, increase their power, vent frustration, get attention, etc. They did a study of which story reduced lying more...The Boy That Cried Wolf or the story of George Washington cutting down the cherry tree. Believe it or not it was TBTCW didn't cut down lying at all. GW's story did - reduced 75% in boys and 50% in girls. In the BTCW the boy ultimately gets a kind of punishment. Kids that live in constant threat of consistent punishment don't lie less but become better liars. GW however got both immunity and praise for telling the truth. "I won't be upset w/ you if you cut down the tree but if you tell the truth I will be really happy." Kids are trying to please us! Also a good point they brought up is that kids learn to lie from us - tell a telemarketer we are just a guest here, etc.
They advise to keep teaching your kids that lying is wrong but once we catch a lie have your approach be different.
I highly recommend the book. They also talk about the inverse power of praise - we should be praising the EFFORT. Why white parents don't talk about race. Teen rebellion, the sibling effect, etc. A variety of topics. They have performed studies on everything to come up with their information.
Good luck!