Visual specificity effects on word stem completion: beyond transfer appropriate processing?

An important, but poorly understood, aspect of memory retrieval concerns the conditions under which priming is influenced by perceptual changes in the form of target items. According to transfer appropriate processing perspectives, perceptual specificity effects on priming require a study task that focuses attention on the perceptual, rather than semantic, features of the items. Other research suggests that perceptual specificity effects are enhanced by conditions yielding high levels of explicit memory. The present experiments manipulated encoding tasks and other variables known to influence explicit memory (repetition and retention interval) in order to gain insight into the determinants of perceptual specificity effects on visual word-stem completion. In Experiment 1 we found that perceptual specificity (letter case) effects on stem completion priming depend on perceptual encoding when subjects' awareness of the study-test relationship is limited. In Experiments 2-4 we found that perceptual specificity effects can be obtained after semantic encoding--especially when the study-test retention interval is short. Perceptual specificity effects after short retention intervals were independent of encoding task, and may reflect a form of involuntary explicit memory.