Types of utterances that belong to meta-levels of activity have been singled out in spoken task-focused dialogues between subjects accomplishing a matching task with no visual contact. The types include activity management and planning, global and local (e.g. signals of activity phase); explicit evaluation of the state of joint project, of one's own state or partner's state; retrospective references and accounts; meta-communicative utterances for conversation management; backchannel response: "continuers"; collaborative completion, echoic quotation; repair (self-repair, other-repair); meta-linguistic utterances; meta-communicative utterances having to do with rapport, etiquette, joking, etc. Differences between normal and schizophrenic subjects have been shown in meta-communicative activity supposed to be linked to the management of distributed cognition and creation of shared representations of reality.