Testing the retrieval effort hypothesis: Does greater difficulty correctly recalling information lead to higher levels of memory?

Although substantial research has demonstrated the benefits of retrieval practice for promoting memory, very few studies have tested theoretical accounts of this effect. Across two experiments, we tested a hypothesis that follows from the desirable difficulty framework [Bjork, R. A. (1994). Memory and metamemory considerations in the training of human beings. In J. Metcalfe, A. Shimamura, (Eds.), Metacognition: Knowing about knowing (pp. 185–205). Cambridge, MA: MIT Press], the retrieval effort hypothesis, which states that difficult but successful retrievals are better for memory than easier successful retrievals. To test the hypothesis, we set up conditions under which retrieval during practice was successful but differentially difficult. Interstimulus interval (ISI) and criterion level (number of times items were required to be correctly retrieved) were manipulated to vary the difficulty of retrieval. In support of the retrieval effort hypothesis, results indicated that as the difficulty of retrieval during practice increased, final test performance increased. Longer versus shorter ISIs led to more difficulty retrieving items, but higher levels of final test performance. Additionally, as criterion level increased, retrieval was less difficult, and diminishing returns for final test performance were observed.