Experimentally Examining the Proposed Relationships Among “Rehearsal-based” Effects

Despite the importance of rehearsal to most models of verbal working memory, its role has been recently called into question. Much prior work in support of rehearsal models has centered on the experimental effects of word-length, phonological-similarity, and irrelevant sound on serial order recall performance and the interaction of all three with concurrent articulation. However, recent research has suggested that confounding effects of stimuli, such as orthographic neighborhood, may be the true cause of the word-length effect. While these findings alone have significant implications for modern models of rehearsal, to understand them within the context of modern theories of working memory, they must also be examined through the lens of the phonological-similarity and irrelevant-sound effects. Thus, through a series of three experiments, the influence of neighborhood in each of these effects was assessed, using strict controls for both orthographic and phonological neighborhood size. The word-length effect was significantly reversed; longer words were significantly better recalled than short words. However, the phonological-similarity effect remained significant even when neighborhood size was controlled. The irrelevant-sound effect was significant when stimuli had no orthographic or phonological neighbors, but was eliminated when stimuli had both. These findings present significant problems for common memory models that include a role for rehearsal, as the relationship between “rehearsal-based” effects was more tenuous than may have otherwise been anticipated