The journal clubs are platforms for inspiration and for talking about the science which may have implications for and may stimulate our own research in new and exciting directions; and for learning interactively what is good science. Students are especially encouraged to join in.
The discussions tends to be stimulated by either questions regarding methodology and theory behind the the chosen paper or extensions and applications of the work described. There are only two requirements for the participants: curiousity and that you have read the paper. How active you are in the discussions is up to you.
On the mailing lists you will get reminders about the sessions, and occational discussions about the journal club and possible papers for discussion etc.