<sup>Originally posted on [Math.SE](http://math.stackexchange.com/questions/702044),
but it was suggested cogsci.SE would be a more suitable venue.</sup>

I'm aware of two publications that have trickled onto the radar screens
of non-specialists:

- [Fortune favors the bold](http://web.princeton.edu/sites/opplab/papers/Diemand-Yauman_Oppenheimer_2010.pdf) by *Diemand-Yauman & Oppenheimer*
- [Designing Effective Multimedia for Physics Education
](http://www.physics.usyd.edu.au/super/theses/PhD(Muller).pdf) by *Derek Muller*
([TED talk](http://www.youtube.com/watch?v=RQaW2bFieo8))

The former focuses on the impact of "disfluency" on retention and success when processing written material and The latter seems to focus on learning in the 
case where preexisting misconceptions need to be corrected (physics).

I'm interested to hear about similar research results in the learning of
abstract concepts, specifically mathematics.

The motivation described in the original question on Math.SE is the
fact that many mathematicians seem to hold the (painful, to students) 
belief that forcing students to struggle (in some sense) is beneficial.
I've quoted multiple examples of this attitude from various sources in 
the original question, you are welcome to have a look.

Does current research support the belief that (in mathematics) difficult
learning is better learning?