A feature model of immediate memory is presented, and simulations are described. List items are characterized as multiattribute vectors that can be selectively overwritten by subsequent external events and by the ongoing stream of internal activity. Degraded primary memory vectors are compared with intact secondary memory vectors, and retrieval likelihood is computed as the ratio of similarities. The model is shown to account for the major modality-based phenomena of the immediate serial recall literature, including modality-based temporal grouping effects and the negative effects of phonological similarity.
251The ability to reconstruct recently presented information as it recedes backward in time is basic to a fully functioning cognitive system. The interpretation of spoken language, among other examples, requires the preservation of temporal order information, a task that is typically assumed to be a critical function of primary, or short-term, memory. This article describes a simulation model that handles a variety of phenomena characteristic of immediate retention. The model is based on an earlier descriptive framework (Nairne, 1988); its main appeal is to the composition of list traces in primary memory and to the manner in which trace composition might change as a function of interference from externally presented events and ongoing cognitive activities. The focus of the simulation studies is on modality-based effects in immediate memory. These effects are quite large and stable empirically, and their analysis exploits the feature-based properties of the model. In a later section, I apply the proposed mechanics to a range of other benchmark data in the immediate memory literature.Of the many variables that can affect performance in a task such as immediate serial recall, where subjects are required to reproduce short lists of items in the exact order of presentation, one of the more conspicuous is presentation modality. The modality effect refers to the superior recency performance that occurs for auditory, compared with visual, presentation. Typically, serial recall of auditory and visual lists leads to declining performance over serial position, but, for the last few serial positions, there is a relative auditory advantage (Conrad & Hull, 1968;Corballis, 1966;Craik, 1969;Murdock & Walker, 1969;Murray, 1966). The stimulus suffix effect is a related phenomenon, which is observed when an extra item, usually a word presented aloud, eliminates the modality effect by reducing the recency advantage that is found for auditory lists (Dallett, 1965).The presentation of list information aloud also interacts significantly with the organization of presentation: If a nine-item list is presented with the items in groups of three, separated by short pauses, auditory presentation leads to large grouping advantages, relative to visual presentation, and, within each group, there is a recency advantage for the last serial position (Frankish, 1985(Frankish, , 1989Ryan, 1969). In addition, under auditory presentation, increa...