Ethologists have studied the way in which information is conveyed by intention movements that accompany the expression of emotions. When a dog bares its teeth or wags its tail, it communicates its likely subsequent actions, communication which both humans and other species understand. Such communications are adaptive and allow members of a species to live in close proximity and to interact efficiently. Ethologists also believe that primates, including humans, use nonverbal cues (facial expressions, gestures, sounds) to indicate emotional states. Movement such as crossing the arms, lowering the head, and standing rigidly, for example, can communicate in body language a negative attitude. Researchers have also been interested in the universality of particular facial expressions as indicators of particular emotions, and some do indeed seem to be universal. But some facial expressions and other gestures differ in meaning from culture to culture and are regulated by cultural norms called display rules.