1 Centre for Research on Networked Learning and Knowledge Building. Department of Psychology. University of Helsinki, Helsinki (Finland). E-mail: sami.paavola{at}helsinki.fi, 2 Centre for Research on Networked Learning and Knowledge Building. Department of Psychology. University of Helsinki, Helsinki (Finland). E-mail: kai.hakkarainen{at}helsinki.fi, 3 Department of Philosophy. University of Helsinki, Helsinki (Finland). E-mail: matti.sintonen{at}helsinki.fi