“…In aging research, forgetting rates have been studied across different age groups and retention intervals and the findings are mixed. Whereas some studies reported differences in initial performance, but invariant forgetting rates in older and younger adults (Fjell et al, 2005;Rybarczyk, Hart, & Harkins, 1987;Spikman, Berg, & Deelman, 1995), others have shown greater forgetting in older adults, especially after long delays (e.g., 1 week; see Huppert & Kopelman, 1989;Park, Royal, Dudley, & Morrell, 1988), or when testing individuals on episodic recall, rather than recognition tasks (MacDonald, Stigsdotter-Neely, et al, 2006). With respect to experimental manipulations, encoding factors such as meaningfulness of the material (Underwood & Richardson, 1956), degree of learning (Slamecka & McElree, 1983), and pictorial elaboration (Forbes & Reese, 1974) have been found to affect initial rate of learning, but not rate of forgetting.…”