For this reason, Clan members are highly adept at reading body language and cannot be deceived by lying; while one can spell an untruth with one's hands, one's posture will give it away. Consequently, the idea of telling an untruth is alien to Clan culture, a fact that Ayla needs time to conceptualize and understand. However, a Clan member can "refrain from mentioning" something she would prefer other people did not know, even though residual clues would probably reveal that something was being concealed. Cultural conventions, Auel suggests, would cause other Clan members to ignore the concealment out of sheer courtesy, though, again, Ayla has trouble grasping this concept.