Durante el proceso resolucion de una situacion problema que involucra un sistema de engranajes en contexto de juego manipulativo, las acciones de ninos(as) de 4 anos muestran planes y procedimientos que evidencian el uso articulado de herramientas cognitivas de formula hipotesis y experimentacion. Se identifican las transformaciones del funcionamiento cognitivo en los cambios de formatos de representacion de conocimientos: exploratorio, intermedio y resolutorio. Participan 60 ninos(as), en cuatro intentos de experimentacion y dos aplicaciones con intervalos de 15 dias. Se privilegia una perspectiva procedural y se apoya en la metodologia microgenetica. A traves de los intentos, el nino elabora premisas, las transforma, las comprueba y extrae conclusiones, re-elabora o genera nuevas premisas, avanzando en su proceso de comprension. Palabras Claves: Cambio cognitivo, formulacion de hipotesis, experimentacion, razonamiento fisico During the process resolution of a problem that involves a system of gears in context of manipulative game, the actions of 4 year old children show plans and procedures which they demonstrate the articulated use of cognitive tools to formulate hypothesis and experimentation. The transformations of the cognitive operation in the changes of formats of knowledge representation are identified: exploratory, intermediate and resolving. 60 four-year-old children participated in four attempts of experimentation and two applications with intervals of 15 days. A procedural perspective is privileged and it leans in the microgenetic methodology. Through the attempts, the child elaborates anticipated, transforms them, verifies them and draws conclusions, re-elaborates or generates new premises, advancing in his process of understanding. Key words: Cognitive change, formulation of hypothesis, experimentation, physical reasoning.