  I describe an activity created to help our students learn how to write a
scientific paper by reverse engineering a contrastive set of existing papers. I
look at three recent implementations of this activity and use a multiple
cognitive models approach to begin understanding the variance. This leads to a
reasonable strategy for further investigation. First, I describe the conception
and design of the activity structure, and how a contrastive set was
constructed. I create an initial coding scheme to characterize group behavior
in the three implementations, with special attention paid to analyzing student
dialog on the structure of scientific papers and their ideas about the reasons
for the peculiar features they observe. There is a striking difference in the
way students engaged with the activity between the implementations not all of
which can be ascribed to differences in activity structures, and the remainder
of the paper is concerned with the use of resources and framing, case-based
reasoning and Gibson's ecological perspective to understand the reason for this
difference.
