The hereby research pretends to determine what is the didactic unit influence about “la circulacion de los seres humanos” during the cognitive development of the 2ndB grade students at Institucion Educativa San Vicente Hogar, located in Pereira, it has been evidenced that the levels of argumentation in the students are poor. Its methodological design of the research is focused on the (cuasiexperimental) quantitative type. During the project it was applied a diagnosis test or pretest, next, a treatment or intervention was done including a didactic unit built and based on the “pequenos cientificos methodology” which tries to influence in the usage of the four argumentation components (basic knowledge, evidence use, justification, conclusion) finally, it was applied a test (post test) to analyze the changes shown in the group. Also, the results from the students in the test are shown with the respective analysis. This research permitted to show how important and meaningful the design of a didactic unit with the “pequenos cientificos” methodology can be to develop the argumentative skill. It was also evidenced that students got meaningful learning when using argumentative elements.