A person's personal space is carried with them everywhere they go. It is the most inviolate form of territory.[8] Body spacing and posture, according to Hall, are unintentional reactions to sensory fluctuations or shifts, such as subtle changes in the sound and pitch of a person's voice. Social distance between people is reliably correlated with physical distance, as are intimate and personal distance, according to the delineations below. Hall did not mean for these measurements to be strict guidelines that translate precisely to human behavior, but rather a system for gauging the effect of distance on communication and how the effect varies between cultures and other environmental factors.