The characteristics of private and social speech produced during a referential-ecological communication task were analyzed through a new category system. Thirty subjects of 8 years old and 30 of 10 years were paired in order to carry on the task in tryads, which were formed by a speaker, a listener and an experimenter. The grade of intervention of such tryads was similar at both ages. Moreover, a considerable communicative fluency in the overall subjects was shown, since the experimenter's participation was very low and inferior with respect to the speaker and listener (which showed a similar level of intervention and adopt their respective roles). As far as the private speech is concerned, the audible form was significantly more frequent in the speakers than in the listeners, only at 8 years of age. Finally, the listener produced significantly more inaudible private speech than the speaker, at both ages. Aspects as the evolution of private speech, the characteristics of task and the listener's motor action are discussed.Se analizan, mediante un nuevo sistema de categorías, las características del lenguaje privado y social producido durante una tarea de comunicación referencial ecológica. Se aparearon 30 sujetos de 8 años y 30 de 10 años para realizar la tarea en tríadas, formadas por un emisor, un receptor y un experimentador. El grado de intervención de dichas tríadas fue similar en ambas edades. A la vez, se evidencia una considerable fluidez comunicativa en el conjunto de sujetos, dada la muy baja e inferior intervención del experimentador respecto a emisor y receptor (los cuales muestran similar nivel de participación y asumen sus respectivos roles). Respecto al lenguaje privado, únicamente a los 8 años la forma audible es significativament más frecuente en los emisores que en los receptores. Finalmente, el receptor produce significativamente más lenguaje privado inaudible que el emisor a ambas edades. Se discuten aspectos como la evolución del lenguaje privado, las características de la tarea y la acción motora del receptor
