The goal of this study is to analyse the influence of the visual analysis skills on the student modelling activities in a web-based learning environment. The influence of collaborative work was also tested. Thus, 131 French high school students working individually and 116 in pairs used the environment Cell World. The environment recorded the outcomes of a sequence of modelling operations into log-files. The students' visual analysis skills were assessed individually in pre-and post-tests. The

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... nalysis of the log-files has shown that cooperative work allows better performances at the very beginning of the modelling sequence. However, the difference of performances between collaborative and individual workers is not anymore different during the rest of the following operations. The results show also that low-performing modellers are lower in visual analysis skills than highperforming modellers. Keywords -visual analysis skills, collaborative work, webbased environment.