We can determine when someone is trying to deceive us by paying attention to their nonverbal behavior, such as eye behaviors or body movements. Some people get nervous and may fidget or twitch while trying to deceive an someone. If we know the person well enough, we may be able to pick up on this right away. If we do not know them, we still need to pay attention to their nonverbal behaviors. There is not so much a conscious effort to control our nonverbal behaviors.
Words are arbitrary.
Language is based on experiences. Not everyone experiences the same things, thus, everyone has a different frame of reference in which they use language. Each person is privy to a connotative and a denotative definition of a word. The connotative definition is based on our experiences because we can relate a word with an experience. This could be an enormous limitation.