A few years ago, we switched to the Matter & Interactions
curriculum for our introductory classes. This has not been
without its hiccups, among them the fact that there has been a
small decline in the conceptual learning gains measured by the
Force Concept Inventory, the oldest and most widely used of the
conceptual tests favored by the Physics Education Research
community. We’ve spent some time discussing whether this is a
temporary glitch, due to the transition, or something inherent
in the curriculum. (Our numbers are small enough that these
results remain at the level of plural anecdotes.)  Yesterday,
via ZapperZ, I ran across an arxiv paper showing that we’re not
the only ones to see this:  The performance of over 5000
students in introductory calculus-based mechanics courses at the
Georgia Institute of Technology was assessed using the Force
Concept Inventory (FCI). Results from two different curricula
were compared: a traditional mechanics curriculum and the Matter
& Interactions (M&I) curriculum. Post