As Derwing (2010) observed nearly ten years ago, one of the goals of pronunciation research is to identify how different aspects of second language (L2) speech develop over time, providing teachers with information on the pronunciation problems that will work themselves out, versus those that will likely pose an ongoing challenge. At the same time, research must account for the cognitive, socio-affective, and experiential variables that shape pronunciation learning outcomes (Moyer, 2014a, 2014b).