The articles in this special issue have triggered memories of the events and research findings that led us to the idea that difficulties can be desirable, but they have also emphasized the complexities and challenges of trying to incorporate such difficulties into teaching and self-regulated learning. Before we go on to comment on the individual papers in this special issue, we provide a bit of history with respect to the considerations that led to the idea that difficulties can be desirable.

In the framework we titled A New Theory of Disuse (Bjork & Bjork, 1992), which was written for a Festschrift honoring William K. Estes, we tried to capture what we labelled some “important peculiarities” (p. 36) of human learning and memory. We came up with the somewhat awkward title for our framework by reference to Thorndikc’s (1914) original Law of Disuse, which stated that learned habits, without continued practice, fade or decay from memory with the passage of time. We wanted to give Thorndike credit for emphasizing that use is critical for keeping memories accessible, but to also point out that the decay idea, which remains appealing to most people, had been completely discredited by McGeoch (1932) and others. Instead, we wanted to convey that memory representations remain in memory, but can become inaccessible—other than, perhaps, in the presence of rare and unique cues.

In our Festschrift chapter we sought to provide linkages to some of the dynamics that emerged from Estes’ stimulus fluctuation theory,...