In order to give the child the impression that a character is listening to their stories, we have invented a clever mechanism that captures the motions and speech of a child using sensors and audio processing. Continuing in the vein of research on story-listening toys, we have built Dolltalk to encourage children to tell and act out original stories. Dolltalk consists of two dolls and a system that records and plays back the stories. The playback alters the pitch of the childs voice higher or lower depending on which doll is supposed to be speaking. Children play with their customized dolls and tell their stories, which are recorded and played back with the same content but with different voices. Dolltalk gives the illusion that it can truly listen by analyzing their physical gestures and speech.
(Source: http://tangible.media.mit.edu/projects/dolltalk/)