For lab meeting this week we're reading a testing effect review by Rowland (2014). It is a heroic effort. The main ideas are summed up well on p. 21, in the Conclusions section, where it is noted that a retrieval difficulty hypothesis is supported, whereas a transfer-appropriate processing account is not. Additional support was found for semantic elaboration accounts, like Mary's mediator hypothesis, but the bottom line is that currently, no one unifying account can explain all testing data.
Another interesting finding was that benefits of testing emerged immediately as well as a delay, which dovetails with some things Karpicke has been saying lately about the "crossover" in testing being an artifact of test difficulty and item selection effects.
The somewhat unsatisfying, but honest, conclusion is on p. 22, where it is stated that "the underlying mechanisms that produce the effect remain elusive," and that "the testing effect is likely to reflect multiple memory mechanisms." In other words, there's lots more work to be done.
The IRB for my main research line was expiring soon, so this morning I submitted a continuing review form to keep it open, noting that 63 additional subjects had been consented since the last time I did the review. I also added Lena to the IRB so that she can help with data collection in the case that I am incapacitated (or, more likely, am unable to make into the lab for whatever reason).
Edit: The IRB has been approved.