Pollution phenomena are complex systems in which different parts are integrated by means of causal and temporal relationships. To understand pollution, children must develop some cognitive abilities related to system thinking and temporal and causal inferential reasoning. These cognitive abilities constrain and guide how children understand pollution processes. Hence, ascertaining whether changes among children's ideas of pollution are related to system thinking and inferential reasoning abilities could be useful in improving environmental education. Eighty participants between 9 and 16 years old were interviewed to evaluate how children explain different aspects of pollution-related systems. From the explanations found in these interviews, three progressive epistemic structures were reconstructed. The three epistemic structures differ in the type of causal and temporal relationship established by the participants and in the mechanisms that the participants used to relate the pollutant to its effects. IntroductionEnvironmental phenomena, including pollution processes, constitute dynamic complex systems that are characterized by their self-organization and adaptation over time (Assaraf and Orion 2009). A system's existence and functions depend on the interaction of its parts. Hence, the different parts of a system are interconnected, making a net of cause and effect relations where the changes in the status of one or more of the system's parts affect the status of the other parts (Assaraf and Orion 2005). Additionally, in pollution-related systems, the cause and effect relations are typically distant in time and space (IPCC 2007). This could be related to temporal dynamics, such as delays, stocks, and flows (Booth-Sweeny and Sterman 2000) that underlie environmental issues, and the influence of strong positive feedback loops deployed over time (Meadows, Randers, and Meadows 2004/2006). This temporal distance between causes and the effects could be related to what Assaraf and Orion (2005) named the hidden dimensions of the system, i.e. patterns and interactions that are not observed on the surface. Due to these hidden dimensions, the causes of pollution become abstract and difficult to directly perceive with our senses.

The aim of this article is to study the possible influence that exercising a representative role at school may have on secondary school students' willingness to participate politically in society. In order to do this, an analysis was carried out of the answers given by 300 students between 13 and 18 years old, from a school with marked democratic practices, when asked about their experience of democracy at school and their intention to participate politically. The results show that students' willingness to participate in society by means of conventional actions, such as voting, does not depend directly on whether they have exercised a representative role at school. However, non-conventional actions, such as attending demonstrations or supporting boycotts, does have a meaningful relation with the exercise of representative roles in the school. As a conclusion, we highlight that participating in the representation of the school influences the democratic formation of students and their willingness to participate politically in society, although this influence is more closely related to non-conventional actions, such as strikes, boycotts and demonstrations.