Lying is deliberately telling a mistruth. Prevaricating is another word for it. Kids usually do it if they think they are going to get into trouble or if they notice others doing it.
It can be hard to teach aspie children the difference between telling a little white lie to spare another person's feelings or to avoid putting themselves into situations of personal embarrassement and telling a great big whopper.
Even Aspie adults often have trouble with this concept as on the one hand they are told always to be truthful and on the other, that sometimes they shouldn't be.
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Break out you Western girls,
Someday soon you're gonna rule the world.
Break out you Western girls,
Hold your heads up high.
"Western Girls" - Dragon