Yes, true.

Not to mention that those children who don't have the mental capacity to voice their thoughts and feelings (very young children) will express it in other ways.

In the younger child, it can often be exhibited in ways such as excessive temper tantrums, juvenile verbal abuse (EG: "You're a fat cow!"), damage to personal property, physical violence and even self harming.

For a child younger again (the infant and toddler) it is often exhibited through health, excessive emotion, continuous sleep issues and many other things.