Functional characteristics of the inner voice and the inner ear: single or double agency?

Double agency theories of short-term memory posit the functional independence of a phonological store (inner ear) and articulatory process (inner voice). A series of 5 experiments challenges this view. Articulatory suppression during retention of 9-item lists gives rise to a changing-state effect similar to that shown for irrelevant speech. Also, vocalized suppression is more disruptive than silently mouthed suppression, but this difference arises from vocalization itself rather than from any auditory feedback to which it gives rise. Class similarity between the to-be-remembered items and the articulatory material is not a critical determinant, but the effect occurs only with tests of serial order. For mouthed suppression, the irrelevant speech effect is only attenuated with changing-state suppression. Also, the presence of changing-state irrelevant speech abolishes the changing-state effect of articulatory suppression. Functional equivalence of codes from auditory, visual, and articulatory sources is claimed.