“…Studies making more naturalistic observation often just de ned a prompt, in the absence of which communication was considered spontaneous or initiated (e.g., Charlop & Trasowech, 1991;Duker & van Lent, 1991). Quite a number of studies were concerned with conversational interactions and such research tended to adopt de nitions associated with sequencing of turns or topic shift (e.g., Dattilo & Camarata, 1991;Haring, Roger, Lee, Breen & Gaylord-Ross, 1986). However, the common characteristic of all de nitions was the treatment of spontaneity or initiation as a binary variable such that communicative acts were either initiations or responses.…”