Towards a Model of Face-to-Face Grounding 
 We investigate the verbal and nonverbal means for grounding , and propose a design for embodied conversational agents that relies on both kinds of signals to establish common ground in human-computer interaction . We analyzed eye gaze , head nods and attentional focus in the context of a direction-giving task . The distribution of nonverbal behaviors differed depending on the type of dialogue move being grounded, and the overall pattern reflected a monitoring of lack of negative feedback . Based on these results, we present an ECA that uses verbal and nonverbal grounding acts to update dialogue state . 