I agree with homeschoolmom. My almost 4 yr old dcg used to lie a lot, it has decreased quite a bit actually. I used to ask "did you do....?" and she would say no. I kept telling her that I don't like to be lied too and if you lie you get into more trouble when the truth comes out. Now I just tell her "I saw you..." and I either tell her that I don't like that behaviour or if it's something major she gets a time away from the group.