Inferential processes in four year old children are observed using a task that involves coordinating up to fi ve classifi cation criteria. Three types of probabilistic reasoning were found : riddle (37.8%), transitional (22.2%) and solving (40%). The riddle search type is the outline of a relationship between “space search” and sample space reduction based on individual concrete actions (interventions) applied directly to the task. The transitional search type is an experimental laboratory that allows the child to observe the relationship between interventions and the outcome of those actions where an intra-variable conditional probability is generated. The solving search type crystallizes a coordination that involves classifi cation operations with sophisticated levels of abstraction since they demand the intersection of two or more variables.