Introduction: This research addresses preschoolers' intuitive understanding of rectilinear movement and some variables which affect it, and the type of arguments used when related knowledge states are justified. A first working hypothesis is that the resolution of practical, functional situations would be based on self-regulation processes. A second working hypothesis is that feedback provided by the situations would modify their levels of epistemological understanding. Method: The sample is composed of 40 boys and girls between the ages of 5.0 and 5.5 years, selected randomly from three private preschool educational institutions in Cali (Colombia), and subsequently assigned to two groups. The experimental material consists of four isomorphic situations based on a task by Chen and Klahr (1999). Results: Data support the first hypothesis: the average number of actions increased significantly between sessions, strategies undertaken by the children are organized in more complex series and with greater effectiveness. Empirical support for the second hypothesis is not supported, most arguments which the children use to describe the knowledge of characters in the situation remain stable. Discussion: A self-regulation process was identified in the children's verbalizations, which moved from mentioning actions undertaken on the material to controlling actions in advance. Positions such as that of Schauble (1996) are discussed, stating that preschoolers are hesitant to abandon strategies despite their uselessness. The activity was ineffective in transforming the arguments they use and by implication their levels of epistemological understanding. (Contains 2 tables.)